Cool air stopped after 300 miles?

[GulfcoastPnut]

Thrilled new owner of a '92 400E, I picked her up in Houston last weekend and drove the 500 miles home. At about 300 miles into the trip there was a couple of minutes of intermittent "squealing" much like regular (metal->metal) brake wear indicators seeming to originate from the passenger side. Almost immediately after that happened and stopped the air went from dried and cool to humid and outside temp.

FWIW the PO knew the car to loose freon over the course of a couple of months so he topped it off for me before we got there and it blew cold wonderful air for the weekend and that first 4-5 hours of the trip home. I did stop at the next exit and bought a can of freon to see if it had just escaped that quickly but the system still read completely full (according to the little can's gauge).

I've been reading from this board as well as others the last few days trying to figure out where to start? Some posts that sounded familiar indicated the Base Module (that I've now learned to be living in the direct spot I heard that odd noise from) could be a common culprit. I have checked fuses inside that vault and on the driver's side with nothing blown.

Could the more knowledgeable weigh in on where to start so cool air will come back into my life? How likely is that Base Module to be bad, how would I know, how would I know that a replacement was good?

Thank you for the help!

 

[nocfn]

UGH welcomes under ugly circumstances. I am sure you will get some E400E owners discussing this asap with you. Should check pressures with gauges, do you smell and "Band-Aid" smell that is R134-A? do you have any green drainage on the ground under the transmission tunnel?

 

[gsxr]

The BM / GM (Base Module / General Module) is just a power supply. It doesn't make any noises. However, if the module senses the compressor speed varying from engine speed (due to a slipping belt, bad compressor speed sensor, or compressor binding)... it will kill the compressor until the engine is re-started.

The 1992 models have a manual belt tensioner that is failure-prone if not OE and/or over-tightened. First thing I'd do is check belt tension, belt condition, and tensioner condition. Remember the tensioner center bolt MUST be loosened before adjusting tension, then re-tightened. The factory service manual is online at this link, see Group 13 for belt / tensioner info.

Second thing will be to buy or build a blink code reader (assuming you have no access to a digital scanner / SDS), clear all codes, drive car, then see what codes return. Don't waste time posting the fifty billion codes currently on all the modules as they will be useless. See the forum "De-Coding" section for details on this. The chances of your Base Module being defective is between slim to none, but you never know...

If the car is losing refrigerant rapidly, you need to identify the leak source. If it's anything except the evaporator, replace the offending item and pull vacuum / recharge properly. If it's the evaporator, you'll probably want to try CryoSeal or Cliplight Super Seal / Total Auto before sinking ±40 hours DIY labor into the evaporator replacement. Search the forum for other threads discussing this.

BTW, congrats on the purchase and welcome to the forum!

 

[a777fan]

ANOTHER pedestrian owner newbie!

!!!

 

[GulfcoastPnut]

Thank you for the welcomes!

So far I have checked out the belt, it appears new (there was a crusty one in the trunk in a bag) and feels properly tensioned, and I've felt the clutch turn smoothly with the car off. I haven't yet had a chance to do the "short the dryer trick" since I'm waiting on a set of gauges and want to confirm what I think (that the leak is still tiny and that freon level isn't the current problem).

Am I mistaken in my understanding that the 500E board is the most appropriate place to gather general engine-bay knowledge for my 400E?

 

[gerryvz]

Am I mistaken in my understanding that the 500E board is the most appropriate place to gather general engine-bay knowledge for my 400E?

No, you are not mistaken. This forum has been serving the 500E/400E community for 10 years as of this coming November 30th.

And, one of the foremost world experts in these cars, our member "Klink", is located very much local to you. You may want to reach out to him.

You should be able to find the answer to just about any question you could have about your car on this forum. I'd say about 80-90% of the 500E content here applies directly to the 400E; that which doesn't, you'll find in the 400E sub-forums.

Cheers,
Gerry

 

[nocfn]

I told you that folks would get you in the right direction!

 

[TerryA]

GCPnut,

Welcome to the forum!! I second Gerry’s suggestion in regards to contacting Klink if you can’t solve your problem. You could not find better help. I’m formerly from New Orleans and feel your pain w/ no A/C. Where you live A/C is an essential you cannot do without.

The 400E is a great car and very dependable. Once you get some of the nitpicking stuff taken care of you will enjoy your new ride.

Good Luck & WELCOME AGAIN!!

 

[GulfcoastPnut]

Well, if anyone is curious, she was completely out of Freon. Obviously I have some significant leak I need to trace down next but I'm glad that it seems the components themselves are operating properly, a recharge and she's blowing ice cold air again.

 

[gerryvz]

I recommend that if you are going to do the leak detection yourself, that you use an electronic "sniffer" Freon detector rather than UV dye. Much easier and faster to track down leaks that way.

Did you just add R-134a from a can?

 

[GulfcoastPnut]

Thank you, that will be my next purchase (I need to do the same to my other old car).

I bought a set of gauges and found both the high and low to be zero'd out. I did fill it from a can (the one I bought while on the road trip), after which I got what seem to be a little low readings on the gauges being ~40 on the low side and something a bit higher on the high side. What should they read for this car properly charged?

 

[nocfn]

I have a table, I will add it.

 

[GulfcoastPnut]

Nocfn: It won't let me hit the "Thanks" button half a dozen times but consider it hit

So maybe the readings I was getting weren't incredibly far off of where they should have been (the youtube video I watched acted like they should be closer to 100 on the low side). Although the chart doesn't seem to show Mobile, Alabama's 250,000% humidity at 100° we have been getting lately so I'll just have to go w/ the highest line ;-)

 

[nocfn]

Yeap, Houston is a fricken sponge at the moment. BTDT!

 

[gerryvz]

The best thing to do is to pull vacuum on the system before adding/recharging with refrigerant. The gauges will also tell you if your system is holding vacuum, thus is not leaking.

I'd recommend if you can, looking for leaks and then totally evacuating the system of refrigerant and oil if a leak is found. Repair the leak and then start from scratch and add the requisite amounts of R-134a and PAG oil. Then you should be good to go for a few years into the future.

Cheers,
Gerry

 

[gsxr]

So maybe the readings I was getting weren't incredibly far off of where they should have been (the youtube video I watched acted like they should be closer to 100 on the low side). Although the chart doesn't seem to show Mobile, Alabama's 250,000% humidity at 100° we have been getting lately so I'll just have to go w/ the highest line ;-)

Pressures will vary based on ambient temp & humidity, and system condition (charge, moisture, viscous fan working, electric fans working, etc).

As a VERY VERY rough guide, on my 400E/500E's in ~90F ambients and ~25% humidty, with a good system I'll see in the 20-30psi low, 200-250psi high, and vent temps under 50F at idle, dropping to low 40's cruising at 40mph+.

YMMV, yadda yadda...

 

[GulfcoastPnut]

Reviving my thread with new information and continued issues:

So while I certainly have a medium sized leak (for which I've just gotten a vacuum pump in the mail and been reading more about diagnosis) there is at least one secondary problem I'm hoping will ring a bell.

My a/c will decide to cut out here and there much like I originally posted, I know it immediately as the air smells different and turns humid. The compressor clutch turns freely, I took off the contacts to short the temp switch and I believe it didn't kick it on, however when I put them back on it sprang to life. I've driven it all week and it seems like if I leave it on the lowest temp setting and don't touch anything it will work (freezing me out) 95% of the time.

If I begin to fiddle it cuts out a lot of the time
If I hit a big bump it cuts out some times
A full throttle on-ramp lends a tiny belt squeak at a gear change and it cuts out sometimes.

I've determined that most of the time if I turn the system off, count to 20 and turn it back on it will spring back to life.

Where to look oh masterful knowers of more than I....?

 

[nocfn]

When you say you can smell the humidity, are you smelling R134, like a box of band-aid's smell?

The red light for recirculation is illuminated correct... and you are not on the economy side but the full AC and the double arrows are white?

 

[gerryvz]

Reviving my thread with new information and continued issues:

So while I certainly have a medium sized leak (for which I've just gotten a vacuum pump in the mail and been reading more about diagnosis) there is at least one secondary problem I'm hoping will ring a bell.

My a/c will decide to cut out here and there much like I originally posted, I know it immediately as the air smells different and turns humid. The compressor clutch turns freely, I took off the contacts to short the temp switch and I believe it didn't kick it on, however when I put them back on it sprang to life. I've driven it all week and it seems like if I leave it on the lowest temp setting and don't touch anything it will work (freezing me out) 95% of the time.

If I begin to fiddle it cuts out a lot of the time
If I hit a big bump it cuts out some times
A full throttle on-ramp lends a tiny belt squeak at a gear change and it cuts out sometimes.

I've determined that most of the time if I turn the system off, count to 20 and turn it back on it will spring back to life.

Where to look oh masterful knowers of more than I....?

That's totally normal for that heavy, humid air smell to happen a few seconds after the compressor kicks off. That tells you instantly that the A/C is not operating.

There are only a few things that will cause the compressor to cut off. By far the most common is the level of refrigerant in the system (contributing to proper system pressure). Seeing as you have a leak in the system, it sounds to me like your refrigerant level/pressure is right on the line to trigger the compressor, but during operation the pressure drops to the point where the system kicks it off.

Have you tried adding refrigerant to the system so that it stays over the minimum pressure threshhold?

Another thing to test would be the pressure switch itself, but it sounds to me like it's doing its job.

Note that the vacuum pump you have ordered will tell you if/whether your system is able to hold pressure, or if there is a leak. Sounds like you already know the answer to this. So, the problem moves now toward finding the leak. Often it's at a fitting, or at the compressor shaft. If it indeed ends up being the compressor, I recommend just getting a new (rebuilt) Denso compressor. They are not horribly expensive via Amazon or places like AutohauZ.

If you do have to crack open the system, unless you have the proper gauges and equipment to evacuate the refrigerant and oil from the system, I'd have a professional do the work. It's not rocket science, but the proper equipment (and several things are needed) is just expensive enough that it's out of reach of most DIYers ... at least to be able to do the job correctly.

On the push-button unit, there are only TWO settings where the compressor IS NOT engaged, at least occasionally: the "O" (off) position, and ECON (the next button to the left of the "O" button. The other pushbuttons all enable/activate the compressor, based on various ambient and internal vehicle temperatures, and the temp setting at the wheel.

Cheers,
Gerry

 

[GulfcoastPnut]

When you say you can smell the humidity, are you smelling R134, like a box of band-aid's smell?

The red light for recirculation is illuminated correct... and you are not on the economy side but the full AC and the double arrows are white?

That's a good question, I really don't think it smells like bandaids but more like gulf coastal hot wet air (to me?).

I don't think the recirc is on ever unless I intentionally press it, I have tried it on both double arrows and the open up arrow with the same results, economy I want to say is one of the buttons that sends it into a tailspin.

 

[gsxr]

Don't forget to check belt tension, especially on a 1992 which has the manual tensioner. If the belt is at all loose, that will cause the compressor to cut out until a re-start, and it will trigger a fault code stored on the BM/GM. If you need a new tensioner, go with OE ($$$) unless you're willing to gamble on the new made-in-unknown Laso (photos here).

Your mention of a belt squeak at WOT followed by AC dying sure sounds like a belt slipping.

 

[GulfcoastPnut]

That's totally normal for that heavy, humid air smell to happen a few seconds after the compressor kicks off. That tells you instantly that the A/C is not operating.

Oh cool, something normal, that's a start

By far the most common is the level of refrigerant in the system (contributing to proper system pressure). Seeing as you have a leak in the system, it sounds to me like your refrigerant level/pressure is right on the line to trigger the compressor, but during operation the pressure drops to the point where the system kicks it off.

Have you tried adding refrigerant to the system so that it stays over the minimum pressure threshhold?

That is an interesting point and possible cause, I was afraid between the PO and I (and our combined ignorance) I had way overcharged the system and that may have harmed something so this time (after learning just enough to be even more dangerous) I was very careful with my gauges to add refrigerant to only about 28psi, so it very well could be a little low. That also bears out in it cutting out if I have the dial on anything but full blast cold yes?

Sounds like you already know the answer to this. So, the problem moves now toward finding the leak. Often it's at a fitting, or at the compressor shaft. If it indeed ends up being the compressor, I recommend just getting a new (rebuilt) Denso compressor. They are not horribly expensive via Amazon or places like AutohauZ.

My recent reading suggested taking my air compressor (not vacuum pump) with the rubber tipped tool and pressurize the system while soap bubbling it all over the place and that it often could be at the compressor shaft. Thank you for the confirmation about just replacing it if I find it to be the cause as that was what I was coming around to but I'm trying to check off all the other boxes first.

If you do have to crack open the system, unless you have the proper gauges and equipment to evacuate the refrigerant and oil from the system, I'd have a professional do the work. It's not rocket science, but the proper equipment (and several things are needed) is just expensive enough that it's out of reach of most DIYers ... at least to be able to do the job correctly.

*tell me if this is wrong* but my plan of attack here had been to determine exactly what was wrong and replace parts and once I had that actually nailed I would take it to a local shop for the proper purge and refill. Thinking that this would be more cost effective than just handing them the car blindly and say please fix it (that makes me twitch).

Thank you so much (all) for the advice

 

[GulfcoastPnut]

Don't forget to check belt tension, especially on a 1992 which has the manual tensioner. If the belt is at all loose, that will cause the compressor to cut out until a re-start, and it will trigger a fault code stored on the BM/GM. If you need a new tensioner, go with OE ($$$) unless you're willing to gamble on the new made-in-unknown Laso (photos here).

Your mention of a belt squeak at WOT followed by AC dying sure sounds like a belt slipping.

hmm..... it never "squeals" except for this chirp but I should definitely check it then. I bought a fault code reader but I haven't gotten around to playing with it, I'll put that on the to do list.

 

[nocfn]

I'm going to watch the thread, but the compressor is on even in defrost heat mode. But for now, you always want to be sure the recirculation light is on manually and that closes a big flap, keeping hot humid air from coming into the car. Single white arrow should be depressed IIRC (third from the left). When I look at a ccu, I may edit the post... for accuracy as it isn't in my hard memory.

 

[GulfcoastPnut]

One more question (and maybe the recirc manually will do it?) but I always have at least some air coming from the defrost vents, this keeps the windshield fogged on the outside bottom until it's blazing hot outside. Is there a way to turn that off or do I have a flap not operating correctly?

My dash for definite reference:

 

[gsxr]

For normal AC, you press the middle button.

For defogging, you use the 2nd button from the left (next to the max-defrost button)... looks like you have this pressed, in the photo above.

Anyway, yes, you may have a flap not operating correctly. The good news is, the defroster flap is easy to access after removing the passenger airbag, and can be tested / replaced as needed with minimal hassle. The center vent pod, and recirculation (main air flap) pods, both require pulling the entire dash out if any are defective. You can test all pods with the airbag removed, there are 7 vacuum lines you need to apply vacuum to with a Mity-Vac. Search the forum for more info.

This is completely separate from the compressor cutting out, btw.

 

[nocfn]

recirc is next to hazard in the middle, and the third from the left is the AC vent locations to open.

 

[gerryvz]

As mentioned, the three left-hand buttons do enable/activate the A/C given the correct settings (including temp wheel and fan speed selected).

The center button (with the black upper arrow) should NOT be pushing air up to the windshield. That's the way to turn it off.

I use the center button most frequently when I'm using A/C, and ideally in this setting, air should be coming from the center vents, dashboard vents (right and left sides), and I believe some from below the dash.

The recirc button almost totally closes the fresh air intake flaps (leaves a little open) so that interior air is recirculated, rather than replaced with fresh exterior air that has to be dehumidifed and cooled. The recirc is ideal for times when max A/C is needed, as the system doesn't have to work quite as hard as the interior cooled air that is being recirculated is already mostly dehumidified and cooled.

Also, one tip: in A/C modes (best achieved with the second-from-left and center buttons), if you click the temp wheel all the way to cool -- and you should feel a small click at a detent when the wheel is turned all the way to the end of the blue zone -- this activates the "recirc" mode automatically. Just the same as hitting the "recirc" button in the dashboard.

When you push the left-hand "DEFROST" button, it should automatically divert a large amount of the air up to the windshield, and the fan will automatically go to a very high-speed mode irregardless of the fan speed pushbutton setting.

It sounds to me as if you have a vacuum pod that is not working correctly, and not closing the diverter flap that controls airflow to the windshield/defrost area vs. the center and side vents.

For proper operation of the ACC system, check the user manual. IMHO a lot of people don't do this, and thus don't totally understand how the system is designed/programmed to work. In my opinion the US-spec E500E (and W124 in general) ACC system is not optimal, mainly because the fan speeds are both variable (depending on temp selected at the wheel) and fixed (based on the fan speed button pushed), and lacks a manual control. And what seems to happen is that the fan speed that the system "selects" is just a SMIDGE too high or too low for what you really need it to be.

Cheers,
Gerry

P.S. This MB service manual document should help you in the functional description and diagnosis of what does what, when.

 

[GulfcoastPnut]

For defogging, you use the 2nd button from the left (next to the max-defrost button)... looks like you have this pressed, in the photo above.

Dammit! I thought that was footwell and dash operation... feel free to insert "RTFM DA" comment

This is completely separate from the compressor cutting out, btw.

Understood and thank you

 

[gsxr]

The recirc function, when working correctly (all flaps good), closes the intake flaps 100%. There is a time limit, 30 minutes max, after which you can manually trigger it for another 30 minutes. Normal recirc flap position is 80% closed in cooling mode. Footwell flaps are closed when the system is in cooling mode.

If the defrost pod is not working properly, or if there is a different vacuum issue, the default mode is to allow air to the windshield.

As Gerry said, PLEASE read the owner's manual which describes how the system works.

Also read the FSM, job 83-600 here. Section E has details about airflow / flaps:
http://w124-zone.com/downloads/MB CD/W124/Index/Groups/83ClimateControlSystem.htm

 

[nocfn]

Also if you get into the vacuum distributor, consider using a Y connector for 4 and the 7 line together connected to port 4, and place a vacuum tight cap over port 7. This will keep the frosting down while on auto climate. Some will still come out the defrost, but it is quite diminished. (klink tip)

 

[GulfcoastPnut]

The center button (with the black upper arrow) should NOT be pushing air up to the windshield. That's the way to turn it off.

I believe it IS doing this, eventually I will dig into those vacuum pods as recommended starting behind the airbag.

Also, one tip: in A/C modes (best achieved with the second-from-left and center buttons), if you click the temp wheel all the way to cool -- and you should feel a small click at a detent when the wheel is turned all the way to the end of the blue zone -- this activates the "recirc" mode automatically. Just the same as hitting the "recirc" button in the dashboard.

- very interesting, I did understand where the recirc button was and have pressed it once in a while (I really did read through the manual just not totally consumed it apparently) but this tells me I HAVE been activating it as I've taken to leaving it down past the little click all the time now.

When you push the left-hand "DEFROST" button, it should automatically divert a large amount of the air up to the windshield, and the fan will automatically go to a very high-speed mode irregardless of the fan speed pushbutton setting.

This it does do.

In my opinion the US-spec E500E (and W124 in general) ACC system is not optimal, mainly because the fan speeds are both variable (depending on temp selected at the wheel) and fixed (based on the fan speed button pushed), and lacks a manual control. And what seems to happen is that the fan speed that the system "selects" is just a SMIDGE too high or too low for what you really need it to be.

- Amen, I decided this seemed to be the case on the first trip, glad to know it's not just me.

 

[gerryvz]

The recirc function, when working correctly (all flaps good), closes the intake flaps 100%.

Dave, if I remember correctly, the intake flaps are closed about 95%, but not all the way. There is a bit of space (maybe a cm or less?) that they don't close, so there is at least a minimum of exterior air that is let in and mixed with the recirc air. This is so that the same stale air is not recirculated in a near-sealed cabin and that SOME fresh air at least can enter the cabin. I believe "for sure" this is the case with the W126 ACC system, which is near identical to the 124 ACC. I will research this definitively.


UPDATE/EDIT: It appears per MB documentation that there are two recirc modes -- 80% ("leak air") and 100% ("closed"). The system switches between these two recirc modes depending on three factors: ambient temperature outside the car, temperature inside the car, and the setting at the temp thumbwheel.

Here's another good document to read about the ACC system: http://w124-zone.com/downloads/MB CD/W124/w124CD1/Program/Climate/1986.pdf#page=1

 

[GulfcoastPnut]

Gerry, I may have hijacked my own thread, would you mind commenting on post #22 when you have time?

 

[gerryvz]

The vacuum (claps that control WHERE air goes) and air conditioning systems are totally separate, and require two different sets of troubleshooting.

One system creates the cool (and warm) air, and the other system distributes it per the pushbutton and temp units direct it to.

 

[GulfcoastPnut]

The vacuum (claps that control WHERE air goes) and air conditioning systems are totally separate, and require two different sets of troubleshooting.

That's where I think I've managed to "muddy" my process, I'm still focused on the AC system at this moment. I had no idea the vacuum/control system was so separated and extremely intricate until I began reading the 83-600 document....... however this is less of a concern at this very moment as it is not behaving bad enough to get attention until other things are right.

 

[gerryvz]

That's where I think I've managed to "muddy" my process, I'm still focused on the AC system at this moment. I had no idea the vacuum/control system was so separated and extremely intricate until I began reading the 83-600 document....... however this is less of a concern at this very moment as it is not behaving bad enough to get attention until other things are right.

Correct. The A/C system will operate (if working correctly) irregardless of the condition of the vacuum system that directs the cold air (or heat) where it is supposed to go. I'd focus on the A/C system first, then the vacuum/flap control system.

 

[nocfn]

....


UPDATE/EDIT: It appears per MB documentation that there are two recirc modes -- 80% ("leak air") and 100% ("closed"). The system switches between these two recirc modes depending on three factors: ambient temperature outside the car, temperature inside the car, and the setting at the temp thumbwheel.

Here's another good document to read about the ACC system: http://w124-zone.com/downloads/MB CD/W124/w124CD1/Program/Climate/1986.pdf#page=1

The reason for post 31

 

[gerryvz]

Dave, if I remember correctly, the intake flaps are closed about 95%, but not all the way. There is a bit of space (maybe a cm or less?) that they don't close, so there is at least a minimum of exterior air that is let in and mixed with the recirc air. This is so that the same stale air is not recirculated in a near-sealed cabin and that SOME fresh air at least can enter the cabin. I believe "for sure" this is the case with the W126 ACC system, which is near identical to the 124 ACC. I will research this definitively.


UPDATE/EDIT: It appears per MB documentation that there are two recirc modes -- 80% ("leak air") and 100% ("closed"). The system switches between these two recirc modes depending on three factors: ambient temperature outside the car, temperature inside the car, and the setting at the temp thumbwheel.

Here's another good document to read about the ACC system: http://w124-zone.com/downloads/MB CD/W124/w124CD1/Program/Climate/1986.pdf#page=1

Basically what this means is that the flap position / recirc air mode is variable and automatic, and the operator doesn't have direct control over it, at least the fluctuation between leak-air (80%) and closed (100%) modes.

 

[gerryvz]

The reason for post 31

Post 31 is a well-known (TFTSNBN-style) kludge, and IMHO only something for folks who don't want a properly operating system. My former shop in Portland, OR, told me about this "fix" about 15 years ago. In fact, I did it on my former R107, mainly because of the extreme difficulty of getting at the pods on that specific model (makes the 124 look like a piece of cake).

I would not tolerate this on my C126 or E500E, though I realize it's a quick and adequate fix for most people.

I acknowledge it's "Klink-approved"(TM). I wonder if it's GSXR-approved, as well?

 

[gsxr]

Connecting 4+7 has not been researched by the GSXR and currently he has no comment.

There is a GSXR-approved Band-Aid to fix a defective center vent pod, if there is NO air out the center vents... but that's a different discussion.

 

[gerryvz]

Connecting 4+7 has not been researched by the GSXR and currently he has no comment.

There is a GSXR-approved Band-Aid to fix a defective center vent pod, if there is NO air out the center vents... but that's a different discussion.

Sounds like a photo-illustrated HOW-TO for the "auslander" (TFTSNBN) crowd is in order. Once in a while, us pompous nit-wits need to help those proletarians out, ya know ?!?

 

[Klink]

Also if you get into the vacuum distributor, consider using a Y connector for 4 and the 7 line together connected to port 4, and place a vacuum tight cap over port 7. This will keep the frosting down while on auto climate. Some will still come out the defrost, but it is quite diminished. (klink tip)

Connecting 4+7 has not been researched by the GSXR and currently he has no comment

Not really related to the complaint of the thread, but for anyone that wants to know...

To avoid external fogging of the windshield with the acc in a cooling maintenance mode when driving in hot humid climates (and especially at night) you can eliminate the separate control of the defroster flap travel limiter diaphragm, and revert to the limiter being controlled along with the center vent element, as it was from late '70s-mid 80s.
Those of you in drier climates won't know what the hell we're talking about with this topic, so if that's you, don't worry about it...

I don't have time to explain this in depth right now, so here's only the "how to" part of this splendid modification:

Remove the limiter diaphragm vacuum line from the vacuum valve connection #7 (bottom connection), and plug the male hose fitting on the valve with a suitable plug. Female plug #000 987 11 45 works well for this. Using a suitable female Y connector such as 117 078 01 45, connect the now unattached line that was removed from valve fitting #7 and Y connect it to the male valve fitting #4 together with the existing line from #4. This will leave all functionality intact, it will only prevent the opening of the defroster flap 20% position until the system is in a heating mode, so you will still get automatic windshield demisting in winter, but you will no longer have the outside of your windshield being fogged over on summer nights...

 

[GulfcoastPnut]

FWIW, after the OP learned to press the correct button there is no longer cold air coming out of the vents below the windshield..... As suggested above I added a bit more refrigerant and it's behaving better, so I believe Gerry was correct in that I was right on the cusp of the right pressure and caused it to mis-behave. Now back to trying to find and fix that pesky refrigerant leak.

Interesting and helpful for me is that I'm currently applying this appreciated instruction to 2 germans in the same garage that originated across town from each other

 

[GulfcoastPnut]

Don't forget to check belt tension, especially on a 1992 which has the manual tensioner. If the belt is at all loose, that will cause the compressor to cut out until a re-start,

Your mention of a belt squeak at WOT followed by AC dying sure sounds like a belt slipping.

Gixxer gets the prize for the week - I took his advice and tightened the belt just a bit last Saturday, I've driven my 400 all week with no squeaks and no interruption of the cold air at all. It had become a several times/ 16 miles to and from work occurrence.

I'm really glad intimate knowledge such as this is still available somewhere. I still have work to do to make her "right" but I'll keep chopping away a little at a time.

Thanks all, Travis

 

[GulfcoastPnut]

Not really related to the complaint of the thread, but for anyone that wants to know...

To avoid external fogging of the windshield .... when driving in hot humid climates (and especially at night) ....

Those of you in drier climates won't know what the hell we're talking about with this topic, so if that's you, don't worry about it...

I have now fully realized the need to do this as currently I have a choice between freezing my a$$ off or constantly foggy windows. Thank you Klink, I will be following this soon.

 

[GulfcoastPnut]

Understood, my referral to freezing my ass off is that I've discovered that the only time there is no air coming from those vents is when I have the dial set past the detent to max cool. And yes, I'm tired of trying to get my wipers to clear the windshield and not being able to see out my side view mirrors because those windows are fogged on the outside too on an otherwise dry morning or evening (if the side vents are on and pointed toward them).

I'm actually glad to find out that this isn't just my car and a common problem.

 

[Klink]

The reason for post 31

NO, DAMMIT! NO IT ISN'T !!!

Post 31 is a well-known (TFTSNBN-style) kludge, and IMHO only something for folks who don't want a properly operating system. My former shop in Portland, OR, told me about this "fix" about 15 years ago. In fact, I did it on my former R107, mainly because of the extreme difficulty of getting at the pods on that specific model (makes the 124 look like a piece of cake).

I would not tolerate this on my C126 or E500E, though I realize it's a quick and adequate fix for most people.

I acknowledge it's "Klink-approved"(TM). I wonder if it's GSXR-approved, as well?

Gentlemen!

Please note that the thing that Louis is referring to in post 31, and the thing that I elaborated upon have absolutely nothing to do with recirculation air versus fresh air. Nothing. Blutarsky. Zero Point Zero. It is a modification that prevents COLD air from being leaked onto the windshield, which causes fogging on the OUTSIDE of the WINDSHIELD, causing one to frequently activate the windshield wipers in a vain attempt to get rid of it. It is absolutely NOT a “Kludge”
There ARE Kludgy ways of doing this, but this isn't one.The "Kludge" that some speak of is simply the ELIMINATION of the defroster door short stroke functionality. That is NOT what I am proposing, and it is not what "my" modification does.

Something was necessary because the Germans in their phobia of draftiness did not adequately consider driving in hot humid climates especially at night. This problem started when they added the separate functionality of the defroster flap stroke limiter, again, done in an attempt to reduce drafts. This change was introduced with the 124 vehicle, and with the second version climate control on 126 vehicles. The modification that I posted about simply reverts the functionality to exactly what it was on the 1985 and prior cars. Anybody that disapproves of THIS modification simply doesn’t fully understand it yet.

We had to come up with something in Florida to deal with the justifiably MASSIVE number of complaints, many citing safety concerns, from the hairbrained ridiculousness of putting cold air up onto the windshield. We had to do it to just about every 124 and 126 (as of MY ‘86) vehicle that we sold. 107 vehicles weren't afflicted with this issue because they didn't get a separate defroster door short stroke functionality. 107 vehicles retained what were essentially first version 126 functionalities.

Once you perform it on an otherwise correctly functioning system you will experience zero changes other than the newfound pleasure of being able to drive your car in hot and very humid climates at night without triggering your windshield wipers every minute or two or intermittently blasting yourself with hot defrost air, AND the light demisting during warm air output modes functionality will STILL be perfectly intact...

 

[Klink]

Understood, my referral to freezing my ass off is that I've discovered that the only time there is no air coming from those vents is when I have the dial set past the detent to max cool. And yes, I'm tired of trying to get my wipers to clear the windshield and not being able to see out my side view mirrors because those windows are fogged on the outside too on an otherwise dry morning or evening (if the side vents are on and pointed toward them).

I'm actually glad to find out that this isn't just my car and a common problem.

My proposal WILL fix the EXTERNAL fogging of the windshield. It can't help with external fogging of the side windows.

 

[GulfcoastPnut]

My proposal WILL fix the EXTERNAL fogging of the windshield. It can't help with external fogging of the side windows.

Yep, I realize I can close off those vents manually which would solve that problem..... I'm still getting to know this really cool machine but enjoying the hell out of it.