HVAC system inop

[e300d]

Rescuing my 500E continues:

The HVAC system in the 1992 500E is inoperative.

When I click thru the buttons on the console. There is no action. No airflow at all. It appears to be completely dead.

I have replaced the fuse strip already in the engine compartment and I have replaced all the fuses in the fuse box.

The p.o, said that he had the ac system working and he performed the evaporator replacement. I do see a new valve fitted by firewall next to the master cylinder and whole bunch of green dye....


So I need to start looking around:


1. Ident the klima and other relays behind fuse box
2. Check the Climate Control Unit for broken leads
http://www.benzworld.org/forums/w124-e-ce-d-td-class/1637278-ccu-repair.html
3. Check blower motor and blower regulator.

Trying to figure out where to start first

 

[gsxr]

Do you mean that it will not regulate temperature, or that there is no airflow (i.e., blower motor not working)? These are usually 2 very different issues.

 

[e300d]

Edited the description.

I need to start the troubleshooting process of the W124 Climate Control....now how do I do that?:?

 

[Glen]

This is how I would begin troubleshooting:
Recheck all fuses. Determine if it's the CCU or the fan. With the engine running, engage the a/c (or front defrost) and see if the a/c compressor engages. If it does, then the CCU is at least partially working. If the compressor doesn't engage, then suspect the CCU unit. Can you swap from another car?

You can then move to see why the fan isn't powering up. The obvious thing is the strip fuse. If you have a VOM, you can check for power there. If no power, re-check your fuses and relays.

 

[gsxr]

There are two 30A flat fuse strips in 1992, right? One for the radiator fans, another for the HVAC fan? Have you checked both?

Dead blower motor is fairly common, could be the brushes are worn out. As Glen said, check for +12v at both sides of the fuse. You can also check the wiring that connects from the top of the brake booster area, this is what goes to the HVAC fan controller (porcupine).

 

[e300d]

Update!

I was able to get some work done on the car today:\

Condition is that the vent blower does not come on at all..Dead...

I can hear CCU working away and making faint noises.

Suspect- dead blower motor? Or?


What I did:

Put in a new 30 AMP strip fuse and tested for voltage. All checks.

I found the 3 prong plug going to the porcupine ie blower regulator... just above the brake booster. It has the black red and yellow wire.

I turned ignition ON and went to pull some values

Red- 11.6V
Yellow - between 7.2V and 1.8V depending on where I set the CCU control for the blower
Black - ground.

So with some reading online from various sites, looks like the vent blower might just be inop.

Ok, went ahead and removed the rain train to gain access to the blower.

Removed blower and put in on bench. I hooked up a healthy 12.8V volts fresh battery and the blower came to life! What the hell Im thinking?!

Took my multi meter and took the read and blue lead that hooks up to the blower. Ignition ON and again I see 11.6 V coming from the lead wire that powers the blower.

Next thing I do is go back to car and play around with the CCU switches: From Eco to high and low fan.

I am getting 2 values..Either 11.6 or 7.5V if system is turned off with CCU switch at 0.

Not sure what to do next. Would the blower regulator be the culprit? I do not have much trouble shooting especially with electronics .

I have attached some pics below.


Here is a pic of the 3 prong plug above the brake booster:

Here is a picture of vent blower out on bench with some test wire

Upon discovering blower works , I go back and check for Voltage out of the leads that power the blower

So as you can see I am trying to do things right and diagnose and troubleshoot. Any tips would be appreciated.

No idea why the damn blower wont spin. I understand there is another circuit which will not allow blower to come on unless the coolant temp is at a certain value. But I have tried in Defrost mode, auto, eco...high blower . low blower, not a whisper from the vent blower...


Does the blower need over 12V to run? Was that why I got it going with direct battery and now via 11.6 volts from my car? I have my cars battery on a battery tender and it is fully charged.
Thanks
Sebastian

 

[gsxr]

Is that 3-pin female connector clean? Almost looks like corrosion present... check that first.

Blower motor doesn't need over 12v to run. Sounds like your regulator is defective, OR the blower motor brushes are almost worn out, and intermittent. Visually check the brushes, if the little copper braided wire from the brush is near the end of the slot and you can see lots of spring behind it, the motor is near death.

 

[gerryvz]

I would concur .. regulator defective. You also need to solder on new pin bushings and get a new pin bushing plastic housing to replace that corroded one.

I recommend replacing both squirrel cage (fan assembly) and regulator together. You can get these parts via aftermarket of good quality. Since you don't have a 1994 model, you don't have to worry about cabin air filters.

There is a HOW-TO on this fan/regulator (124 models) some time ago, which is located here. Also a relevant thread on this forum, posted here.

Cheers,
Gerry

 

[emerydc8]

With the engine running, engage the a/c (or front defrost) and see if the a/c compressor engages. If it does, then the CCU is at least partially working. If the compressor doesn't engage, then suspect the CCU unit. Can you swap from another car?

That's great information. I guess it could only be one of three things outside of fuses: CCU, regulator or blower. This definitely helps to narrow it down.

 

[gerryvz]

I think it's fairly rare for the PBUs (push-button units) in the dash to go bad. Happens, but blower regulator is much more likely.

 

[emerydc8]

I guess that's good news because, of the three, the CCU is the most expensive. I'm getting that occasional annoying squeak from my 95 when the fan is on low. I was able to buy an extra year or so by oiling the motor on my 94, but I know it's only a band-aid.

I replaced my 94 motor with a Bosch (sans squirrel cages) and was able to pull the old cages off using a heat gun and swapped them out.

Looking at my options, the Bosch motor, without the plug and the squirrel cage, is $104.50 from peachparts. The Behr OEM unit with the fan is $253.43 from autohausaz and $336 from parts.com.

Maybe I'll go with the Bosch motor and replace the regulator as a precaution while I'm in there.

EDIT for e300d: These prices are for the later models with the cabin filters.

 

[gsxr]

Gerry is correct, the PBU's are a relatively rare failure. The issue I've run into most often is the buttons get loose and won't stay on - SuperGlue fixes this most of the time. I still keep a bunch of spares though, when I can find really nice looking ones at P+P from a late 124.

 

[gerryvz]

FYI - new buttons for the 124 PBU are available and will stay on. I think I paid like $12 for an AUTO button via p.com for my wife's wagon and it has been fine. The old one didn't want to stay on....

 

[gsxr]

Being a cheapskate, I used a drop of Yurro glue. Works fine.

 

[e300d]

Small update:
Regulator is no good

Based on what you guys have said and confirming with this test:

Jumped blue wire to ground and got the blower motor on high setting. Based on A.Dalton diagnosis it means a bad regulator aka porcupine


Refrence:
http://www.peachparts.com/shopforum/tech-help/241868-95-e320-no-blower-speed-ccu.html
I will give you the series chain so you can diagnose after you take the readings.

The power goes from Bat + > Ign sw > F15/30 A. fuse link > to Red of firewall connector > blower +.
The yl comes from CP > regulator. That is reg trigger signal and is fused via #7.

If you have 12 v at red/blk and trigger at yl/blk at firewall, then the problem is down at the blower/reg.
Once there , you jumper a wire from the blu blower motor wire to ground. If that gives High Fan, the Regulator is bad.
Notice that the switching for the blower is done on the NEG side [ It is a Switched Ground Circuit], where the RED to blower is Allways HOT w/KO...
Grounding he blu wire from blower By=passes the Regulator, and therefor, that is the Regulator test. If no Variable V signal at Yl , then the reg will not trigger and No FAN can happen.

 

[vatc5637]

My son who is driving the '94 E420 has reported that the a/c suddenly stopped working and that there is no air coming out of the vents (funny how things always seems to happen when he is driving the car, never when I am). Based on this and some similar threads, I will check the blower's 30A strip fuse (including fuse holder), then blower motor and/or regulator when he returns home next week with the car from school. During my search of this and related threads, I did not see any picture or diagram showing precisely where the regulator is located, other than "under the blower motor". If one exists, could someone provide either as a point of reference? Also, I am assuming that the blower motor regulator can be purchased separately from the blower motor, if so, can someone please provide a part #? Thanks

 

[emerydc8]

You can mail your son a 30A fuse and have him install it with a screwdriver. See pic.

The regulator sits under the blower motor (I believe it's under the bracket #78 in diagram) and that requires that you remove the trim at the firewall and base of windshield, along with unbolting the windshield wiper (that's not as hard as it sounds). You will see the regulator once you get the blower and squirrel cage out. There are posts about how to get the blower out. You can order a Bosch motor without the plastic squirrel cage and use a heat gun to help you slide the cages off the old motor and onto the new. Or you could spend three times that amount and get a Behr with the squirrel cages attached. Last I checked they were over $300. Using the Bosch motor 0 130 111 012 http://www.autohausaz.com/search/product.aspx?sid=vwuoipnsvrijf455dmdd53fw&partnumber=0 130 111 012 ($76.76) and swapping squirrel cages requires that you reuse the wires connecting to the old motor and there is a minimal amount of soldering, but it's pretty easy.

The blower and regulator part numbers depend on whether you have dust filters for your blower intake. Since it is a 1994, I would think you have them, but there are a number of "real" gurus here who know the exact cutoff when Mercedes started installing the dust filters in the E420 and they will probably be able to help you on that one if you don't know. My 1994 has dust filters and it is chassis C124424.

See attached diagram and parts list.

ADDENDUM: I checked autohausaz and, presuming you have dust filters, the OEM Behr blower with cage is $253. The regulator is $150. As you can see for yourself, if you don't have dust filters, you are in luck because the motor and regulator are substantially less expensive.

Parts.com and another MB dealer sell the blower (1248200608) for $351 and the regulator (1248212151) for $319.50. It looks like Autohausaz may be your best bet.

You might also want to check with Clark's supplier out of Florida.

Whatever you do, DO NOT BUY A URO in order to save money. You'll be sorry.

 

[e300d]

Hey folks.

To conclude the topic. The blower regulator was the issue. I bought one..not uro parts and all seems to be working...cold ac as well.

Thanks folks.

 

[vatc5637]

Thanks Jon for your response and suggestions. As I'm sure many on this board will relate to, this son isn't one whom I could just send a 30A strip fuse to and have him replace it (as simple as that might seem). He's great with computers, but like his mom, when it comes to cars, all he pretty much knows is where to put the gas in and where the ignition key goes. Besides, given Gerry's recent post, I wanted to check out the condition of the strip fuse plastic holder as well. Hopefully, all it will be is a blown fuse.

This car has the dust filters, plus I had previously checked the blower motor (about 18 mos ago) to remedy a persistent ticking sound from the squirrel cages hitting some loose foam insulation. If need be I will only use 500Eboard approved replacement parts and vendors.

 

[emerydc8]

As I'm sure many on this board will relate to, this son isn't one whom I could just send a 30A strip fuse to and have him replace it (as simple as that might seem). He's great with computers, but like his mom, when it comes to cars, all he pretty much knows is where to put the gas in and where the ignition key goes.

I have friends like this. One of them couldn't even figure out where his windshield washer reservoir was, but I wouldn't want to be his opponent in a courtroom. To each his own.

 

[clarkz71]

I belive the bower regulator varies the ground side.

So having power there is not the real test for function.

The yellow wire at the plug behind the booster is key.

 

[vatc5637]

Just another short note to conclude, got the car back today. Checked out the plastic strip fuse holder, no issues. Even though they looked ok, I changed the 30A strip fuse and 2 16A torpedo fuses in the fuse box for the circuits that touched the climate control system. Started the car, turned on the a/c and lo and behold, cold air blowing from the dash vents. It took me all of 15 minutes and less than $5 for the fuses. Heck, I spent more time (2 hrs) & money ($20) at my local pick 'n pull, scavenging a replacement blower motor (w/cages) and regulator that I thought I was going to need. Well, at least now I have spares. I am grateful to the board and its members for saving me the time and aggravation I know that I would have experienced, if not for the suggestions, knowledge and experience that is so freely shared here.

 

[M104-AMG]

So what's the word on Kaehler and/or K.A.E. blower regulators ? The vendor list shows these as "iffy" for relays, but does it apply to the blower regulator ?

TIA,
neil

BTW: AutohausAZ has Behr blower assemblies for $160!

 

[gerryvz]

KAE relays and regulators are junk ... Meyle quality at best and not advised to use.

So what's the word on Kaehler and/or K.A.E. blower regulators ? The vendor list shows these as "iffy" for relays, but does it apply to the blower regulator ?

TIA,
neil

BTW: AutohausAZ has Behr blower assemblies for $160!

 

[clarkz71]

BTW: AutohausAZ has Behr blower assemblies for $160!

That's only for 92-93 124's without cabin filters

Most if not all 94-95 124's have cabin filters, that blower is $254

The blower regulator is also different based on cabin filter fitment

 

[clarkz71]

 

[clarkz71]

KAE relays and regulators are junk ... Meyle quality at best and not advised to use.

Yep, I have 2 Behr Hella regulators I bought while they still were available

Non cabin filter, part# 124-820-2710, PM me if anyone wants my spare

 

[RicardoD]

Yikes,

I am running into this now (dead blower I believe). Like Gerry says in the 30A fuse thread, on the hottest day of the year, these things will crap out. Anyway step one is fuse maintenance for me. Just ordered what I needed and will start diagnosis work in parallel.

Fuse maintenance: http://www.500eboard.com/forums/showthread.php?t=4890

30A fuses: http://www.500eboard.com/forums/showthread.php?t=4792

My goodness owning this car is such a joy with this board behind me. Although I am in the middle of my Porsche 964 engine rebuild and rather work on that, my E500 is my daily driver, and commuting home in my hot car after work needs to be addressed first. I am slowly working my way through deferred maintenance and little things pop up here and there.

EDIT 5/23/2016: Fuse maintenance did the trick. HVAC blower is working fine now!!

 

[jnes]

Old topic but I have similar issue with my car. Blower won't work. CCU seems to be working, at least it is making some noices and flaps are working. Hot and cold air is coming via free flow. I have replaced regulator about 4 years ago (KAE ) and I thought that my blower motor is dead. I took it off from the car and tested it with battery charger and it is running fine at few seconds before charger's fuse blowed.

I tried to measure voltage and current at regulator power connection at the firewall. No voltage att all. I put regulator pin back on and measured voltage where the power is fed to blower motor and there is no voltage, no matter which button I press in ACC unit. Am I right that there shoud be some voltage between pins ( red and black)?

Is the conclusion that my CCU is dead?

 

[gsxr]

If there's no power at red & black, check the 30A strip fuse.

IIRC, the speed signal from the CCU is via the yellow wire and varies from something like 1v-6v...? CCU failures are not common, but they are easy to swap out with a spare for testing.

 

[jnes]

I replaced 30A strip fuse. No improvement.

I did some measurements and seems to be that I don't have connection between 30A strip fuse and X64 connector. (blower regulator/interior harness connection) Anyone have idea how the wires are routed from strip fuse to X64 connector. Is the wire going at first through the firewall, inside to dashboard and then back to the firewall to the engine bay? Is there any plug or pin connetor inside dashboard?

My previous repair (aftermarket alarm system removal) I have to remove dashboard and I think that there is a minor chance that I might have damaged wires or the connector if there is any connector. Odd is that I do have connection in earth wire in this X64 connector but no power (+12V) or signal connection from the PBU.

 

[gsxr]

First - make sure you are checking the correct 30A strip fuse. There are two different ones which are identical (on pre-facelift cars). The one behind the brake booster is for the twin electric fans in front of the condenser. There should be another one mounted to the driver side strut mount.

After that... I'm pretty sure you should get +12v to the 3-pole connector for the HVAC blower regulator when the ignition is switched on to postition 2 (all lights on in the instrument cluster). If not; it's possible your ignition switch is faulty, but it would be odd if it happened all of a sudden.

 

[nocfn]

I had the following sage advice:

Also, it's a little bit of a pain in the ass to get to, but you can back pin the three wire blower regulator pigtail plug connector under the hood, below the windshield wiper blade, on top of the brake booster/pedal bracket and check the blower control voltage coming from the AC pushbutton unit. It should be somewhere between three and six volts between the little tiny one of the three wires, and body ground. If I am remembering correctly, it is a yellow wire, but it's very easy to tell, because it is a much smaller diameter than the two big blower supply wires.
If you have no or low voltage there, your pushbutton unit could be wonky. That's rare, but it does happen. Sometimes it's just a solder joint inside the pushbutton unit doing that.

In my case-the test was negative and i replaced the blower resistor.

 

[jnes]

Thanks for the tips. I replaced that 30 A fuse which is nearby strut mount. No voltage att all on any pins at X64 connector. Earth connection is working. Both +12V and signal wire doesn't have any voltage. I have replaced ignition switch last summer and driven only about 4000 km after that. I have removed blower motor and regulator.

I opened up the PBU but did not found any bad solderings. Maybe I should order new unit for checking if PBU is faulty. If that is not the fault then I have to check wirings.

 

[dalevel47]

Thanks for sharing!

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