Blower Motor

[emerydc8]

BTW, Jon, it would help to compare the readings from your other car since it's working normally!

That's just what I did. On the good car, with the key on and a/c selector off ("O"), I am getting 12v on the red pin and ground on the black. With the a/c selector in EC and fan in low, I'm getting 10.5 v on the yellow and 12 v on the red. (Black is always ground.) With the fan selector in AUTO I am getting 4.5 v on the yellow and again 12 v on the red. And with the fan on HI I'm getting 10 v on the yellow and 12 v on the red.

So. the problem is that I am not getting 12 v from the red terminal. I'm almost thinking about just tapping off downstream of the 30A strip fuse (I did check and even replaced it), and running it to the red lead of the regulator harness, rather than chase a wiring problem between the firewall, ignition and CCU.

The CCU is not the problem. I bought a spare and got the same results. Then I swapped the known good CCU from my other car and got the same results. No way all three are bad. Plus, the good car CCU works when I put it back. The regulator cannot be a suspect because all these problems are occurring upstream of the regulator.

[UPDATE] Call me a hack, but I decided to tap into the 30 amp strip fuse and run 12v directly into the regulator harness red wire. I don't know why there's no voltage for the red wire at the terminal block but I also don't have the patience to trace it down all the way through the ignition and CCU.

 

[TimL]

Does anybody know if the following blower PN is correct for a 92 car 1248201308?

 

[gsxr]

Does anybody know if the following blower PN is correct for a 92 car 1248201308?

No. That blower is for facelift models only (with dust filter), and also specific to non-USA models with "tempmatik", whatever that is. Screen shot below.

All 1986-1993 USA model years need blower # 000-830-82-08, which is NLA from MB.

 

[TimL]

Thank you- much appreciated Dave

 

[LWB250]

Jon,

Did your red wire bypass hack resolve this? I'm assuming it did?

As an aside, the same system is used on the facelift R129 models in a similar arrangement. I've had to deal with the use of aftermarket regulators on the R129 and found that the regulators that can be bolted to the heatsink seem to last much longer if you remove them and apply high quality heat sink grease used for computer CPUs.

This job may be in my future, unfortunately. Doesn't look like fun.

Dan

 

[Sebastopol]

Thought I would add that I purchased an ACM regulator in late 2019, part was made in France, and the quality looked good (it was an exact fit and wiring quality looked good). I installed this about two years ago and have had no problems since then.

Brian

 

[emerydc8]

Jon,

Did your red wire bypass hack resolve this? I'm assuming it did?

Dan

It did work, but later I discovered from the other car that the lack of voltage/current problem is caused by a bad ignition switch. The car in this string wasn't putting out any voltage at the firewall where the regulator plugs in. I bypassed it with known good voltage downstream of the 30A strip fuse.

In the other car, I was getting voltage, but apparently there wasn't enough current to drive the blower fan, so it caused me to believe the regulators were bad. It turned out that the source for the regulator/fan runs through the ignition switch and there's a copper tab inside the rotary switch that was in the process of breaking off. I haven't gotten around to replacing the ignition switch on this one, but I plan to do so within the next few weeks. Then I can remove the wire and run it through the regulator harness.

What are the chances that I would get a failure of both ignition switches within a six month period?

 

[luckymike]

I

It did work, but later I discovered from the other car that the lack of voltage/current problem is caused by a bad ignition switch. The car in this string wasn't putting out any voltage at the firewall where the regulator plugs in. I bypassed it with known good voltage downstream of the 30A strip fuse.

In the other car, I was getting voltage, but apparently there wasn't enough current to drive the blower fan, so it caused me to believe the regulators were bad. It turned out that the source for the regulator/fan runs through the ignition switch and there's a copper tab inside the rotary switch that was in the process of breaking off. I haven't gotten around to replacing the ignition switch on this one, but I plan to do so within the next few weeks. Then I can remove the wire and run it through the regulator harness.

What are the chances that I would get a failure of both ignition switches within a six month period?

@emerydc8 I think I have the exact same ignition switch issue and am getting ready to place an order.

Following your example, I applied 12 volts directly to the rear connector of the 30 amp fuse and for the first time in MANY months, the fan worked.

I'm wondering where you got your 12 volt feed?

 

[emerydc8]

I

@emerydc8 I think I have the exact same ignition switch issue and am getting ready to place an order.

Following your example, I applied 12 volts directly to the rear connector of the 30 amp fuse and for the first time in MANY months, the fan worked.

I'm wondering where you got your 12 volt feed?

I tapped off the 30A strip fuse behind the brake booster, downstream of the fuse itself, so it would be on the firewall side. See pic.

It's coincidental that you asked about this because I just replaced the ignition switch on this car last night. Tonight, I just went out and confirmed that there is in fact 12v coming from the center (red) post where the blower fan regulator plugs in. So, I can confirm that it was in fact a bad ignition switch that caused the lack of voltage to the center post (red wire) for the blower fan regulator.

I still haven't gotten around to re-sourcing the 12 volts back to the center post through the regulator harness connector. My main concern going into summer was that if the ignition switch was not allowing 12v to the blower fan regulator terminal, then do the radiator cooling fans get power through the same terminal of the ignition switch? I don't know.

I noticed last week that the low speed cooling fans were not working with the a/c running at idle and outside temp at 90F. I was thinking it was due to the bad ignition switch, but after replacing the switch last night, the fans still did not kick in, so I replaced the low speed fan relay., which made no difference. I checked out the terminals for the large low-speed fan resistor and my modifications with heavier-gauge wire and connectors have stood the test of time. It looked good.

The last thing I could think of was that it was just low on R134a refrigerant, so I hooked up the gauges and it turns out I was running at less than 30psi on the low side. I had to add two cans of R134a to finally get the low-speed fans to activate.

Now that presents a question of whether I have developed an a/c leak. The last time I serviced the air on this car was probably several years ago and even with the system pressure running as low as it was, it was still blowing fairly cool air. So it could be a slow leak that I am willing to live with. We'll see this summer.

Fix one problem and discover another! C'est la vie.

 

[luckymike]

Okay, we might have slightly different issues but every post helps me understand this system a little more.

My understanding is that power goes from the ignition switch to the 30-amp fuse to the regulator connector (X64). But if that's right, how did you always have power at the fuse (to tap into) if your ignition switch was bad? See screen grab. You can follow the power from the ignition switch, S2/1, through the fuse, F15, to the regulator connector, X64. I think this explains my issue (no power at fuse so assumed bad ignition switch) but I'd also like to understand what you had going on (power at fuse but not at your center connector at X64). To add to my confusion, the center connector is marked in the screen grab as W1 which is a ground, but you've confirmed 12 volts there! I don't get it.

At any rate, I'll report after my new ignition switch is installed. They're only $34 so I got two! By the way, @emerydc8, did you replace the ignition switch through the cluster opening or did you do the whole lower dash dismantle thing?

 

[emerydc8]

Okay, we might have slightly different issues but every post helps me understand this system a little more.

My understanding is that power goes from the ignition switch to the 30-amp fuse to the regulator connector (X64). But if that's right, how did you always have power at the fuse (to tap into) if your ignition switch was bad?

That's a very good question. When you pull the blower motor regulator connector cap off where it plugs in at the firewall, is the center wire in that connector red? Why would the schematic show it as a ground? When I pulled the connector off the terminal last night, I touched one end of a voltmeter to the center post on the three-pronged terminal and one to a bolt on the strut tower. This was with the key on and the blower control on high. I got 12v.

I removed the front screws for the knee panel and pulled it down. There's only about six screws and no need to remove the black plastic cover further aft of the knee panel--it all dropped down together. I was able to get to everything I needed. The new ignition switch may not be preset to the #1 position, so it took me 45 minutes monkeying around trying to get the correct position that would allow the bezel to lock and key to come out in the 0 position. The instructions (46-8010) don't help much with this. At one point I thought I had it correct but the key wouldn't release in the 0 position. You have to use the special (home-made) tumbler tool to get the snap ring to retract as you push it in and allow the bezel to lock in back. If you get it right the first time consider yourself lucky.

 

[luckymike]

I'll check that center pin voltage this weekend.

So you had to mess with the tumbler? I figured on going in through the cluster opening, turning the key to position 1 to allow the connector to come off the back of the ignition switch, then removing the three screws that hold the ignition switch in place. I did it this way on my W126. Did you try it this way or do you have an opinion on how difficult it would be now that you've been in there?

 

[emerydc8]

I never tried it by removing the instrument cluster. It was too difficult for me to get to those three screws that hold the switch on from the rear. when I tried it with the other car. The screws are recessed into the switch by about an inch and one was starting to strip; but maybe I just didn't find the correct tool for the job.

The way I did it, (with the knee panel pulled down and tumbler removed), I loosened the locking 5mm Allen bolt, disconnected the two electrical connections to the switch (just pull down on them), disconnected the knurled cable attachment on the right that comes from the shift lever, pushed the locking pin in on the horizontal shaft and shifted the whole assembly to the right, which allowed me to rotate it down and back so the back of the switch faced me. Then I pulled the big plastic plug off the rear of the switch and the three screws were easy to get to without stripping them.

IMHO, the hardest part of the whole operation was getting the switch, tumbler and security bezel lined up correctly. The home-made tool has to be inserted during this installation process because that's what allows the snap ring in back of the tumbler to retract and let the bezel slide over it to lock in place. I tried setting the switch to what I thought was position 1, but it didn't work so easily. If you did this all the time, I'm sure it would be easy but for me, I struggled. You will think you have everything right, but then you can't turn the key to position 0 because the tool is preventing it. I eventually got it right, but I don't really know what I did. I can't imagine how difficult it would be if I couldn't see it from the front, but if you've done this before without removing the tumbler, maybe it's a better way.

I never considered going in from the instrument cluster hole because the WIS (at least what I looked at) showed one job for removing the tumbler and another for removing the whole switch assembly. Let us know how it goes for you; and if you're successful, a HOW-TO with pics would be appreciated.

 

[emerydc8]

At any rate, I'll report after my new ignition switch is installed. They're only $34 so I got two! By the way, @emerydc8, did you replace the ignition switch through the cluster opening or did you do the whole lower dash dismantle thing?

Any progress on getting to the ignition switch from the instrument cluster opening?

 

[luckymike]

Any progress on getting to the ignition switch from the instrument cluster opening?

No. Still waiting for the ignition switch to arrive from Naperville. Hoping it arrives before our 2-week road trip tomorrow. I want to have it with us just in case.

 

[Seangbadee]

The OE regulator can be removed, and the thermal paste replaced, although Im not certain how much difference fresh paste makes. The regulators will eventually fail, but can last a long time. Its tougher if you dont know how old it is, i.e. if a previous owner already had it replaced.

Ive only recently discovered that the regulators can start to fail such that they appear to mostly work fine, except high speed isnt as high as it should be... more of medium speed. I noticed the high speed was wimpy on my high-mile (240k) E420 daily driver and was scratching my head as to why. Long story short, the regulator was the culprit. Measuring current draw will identify if this is an issue; the wimpy high speed was only pulling 15-18A, and with a good regulator high speed should be around 25A. Use an inductive clamp-type ammeter at the 30A strip fuse to measure current draw. EDIT: Make sure the ammeter will read DC current! Less expensive ones only read AC current.

When a regulator has totally failed, you either get zero fan (assuming the motor is good), or a fixed fan speed.

I have to conclude that my regulator is toast. I get only a fixed fan speed (low), and refreshing the thermal paste has not improved or worsened the situation.

 

[Seangbadee]

I have to conclude that my regulator is toast. I get only a fixed fan speed (low), and refreshing the thermal paste has not improved or worsened the situation.

The blower worked at full speed when I connected it to the battery terminals, and after reading Jon's post, I will check my voltages, just in case I have an ignition issue.

 

[Seangbadee]

The blower worked at full speed when I connected it to the battery terminals, and after reading Jons post, I will check my voltages, just in case I have an ignition issue.

I went ahead and checked the voltages after reading this ..

https://freescruz.com/.priv/W124/w124CD1/Program/Climate/83-600.pdf

My voltages are written in red. Could the issue (slow speed) be the blower and not the regulator? I have noticed a squeal from my vents when the climate unit is on.

 

[gsxr]

My voltages are written in red.

Your control voltages (supplied by the pushbutton unit) appear correct / normal.

Could the issue (slow speed) be the blower and not the regulator? I have noticed a squeal from my vents when the climate unit is on.

If the blower motor ran at full speed with +12v applied directly, bypassing the regulator.... but only runs a a fixed low speed when connected to the regulator... that sounds a classic failed regulator.

On the bright side, the facelift (94-95) regulator A1248212151 should still be available new from MB. Roughly $250 from discount dealers:

124-821-21-51 - Switch 1958-1993 Mercedes-Benz | MB Parts Source

Factory Direct Switch (1248212151) For Your 1958-1993 Mercedes-Benz Vehicle. Up To 35% Off On Every Order And Guaranteed Fit When You Enter Your VIN!

www.mbpartsource.com

Still shows available at MB Classic too, which is great news (for now):

Mercedes-Benz Classic Parts Search.

Browse through the Mercedes-Benz Classic Parts Search to see the availability of parts, promotional and newly manufactured parts and order them online (only in Germany).

partssearch.mercedes-benz-classic.com

 

[Seangbadee]

Your control voltages (supplied by the pushbutton unit) appear correct / normal.




If the blower motor ran at full speed with +12v applied directly, bypassing the regulator.... but only runs a a fixed low speed when connected to the regulator... that sounds a classic failed regulator.

On the bright side, the facelift (94-95) regulator A1248212151 should still be available new from MB. Roughly $250 from discount dealers:

124-821-21-51 - Switch 1958-1993 Mercedes-Benz | MB Parts Source

Factory Direct Switch (1248212151) For Your 1958-1993 Mercedes-Benz Vehicle. Up To 35% Off On Every Order And Guaranteed Fit When You Enter Your VIN!

www.mbpartsource.com

Still shows available at MB Classic too, which is great news (for now):

Mercedes-Benz Classic Parts Search.

Browse through the Mercedes-Benz Classic Parts Search to see the availability of parts, promotional and newly manufactured parts and order them online (only in Germany).

partssearch.mercedes-benz-classic.com

Your control voltages (supplied by the pushbutton unit) appear correct / normal.




If the blower motor ran at full speed with +12v applied directly, bypassing the regulator.... but only runs a a fixed low speed when connected to the regulator... that sounds a classic failed regulator.

On the bright side, the facelift (94-95) regulator A1248212151 should still be available new from MB. Roughly $250 from discount dealers:

124-821-21-51 - Switch 1958-1993 Mercedes-Benz | MB Parts Source

Factory Direct Switch (1248212151) For Your 1958-1993 Mercedes-Benz Vehicle. Up To 35% Off On Every Order And Guaranteed Fit When You Enter Your VIN!

www.mbpartsource.com

Still shows available at MB Classic too, which is great news (for now):

Mercedes-Benz Classic Parts Search.

Browse through the Mercedes-Benz Classic Parts Search to see the availability of parts, promotional and newly manufactured parts and order them online (only in Germany).

partssearch.mercedes-benz-classic.com

I’ll start with the regulator then see if I need a new blower.

 

[Seangbadee]

Your control voltages (supplied by the pushbutton unit) appear correct / normal.




If the blower motor ran at full speed with +12v applied directly, bypassing the regulator.... but only runs a a fixed low speed when connected to the regulator... that sounds a classic failed regulator.

On the bright side, the facelift (94-95) regulator A1248212151 should still be available new from MB. Roughly $250 from discount dealers:

124-821-21-51 - Switch 1958-1993 Mercedes-Benz | MB Parts Source

Factory Direct Switch (1248212151) For Your 1958-1993 Mercedes-Benz Vehicle. Up To 35% Off On Every Order And Guaranteed Fit When You Enter Your VIN!

www.mbpartsource.com

Still shows available at MB Classic too, which is great news (for now):

Mercedes-Benz Classic Parts Search.

Browse through the Mercedes-Benz Classic Parts Search to see the availability of parts, promotional and newly manufactured parts and order them online (only in Germany).

partssearch.mercedes-benz-classic.com

Part 1248121151 is NLA

 

[gsxr]

Part 1248121151 is NLA

Sean, double check the part number. I'm seeing 124-821-21-51 available at MBCC and at RevParts dealers, however you will need to call and talk to a live person at the parts counter if you want to confirm worldwide inventory levels:

 

[LWB250]

I have to conclude that my regulator is toast. I get only a fixed fan speed (low), and refreshing the thermal paste has not improved or worsened the situation.

You've pretty much confirmed the regulator is toast. This is a common failure mode.

Dan

 

[Seangbadee]

Sean, double check the part number. Im seeing 124-821-21-51 available at MBCC and at RevParts dealers, however you will need to call and talk to a live person at the parts counter if you want to confirm worldwide inventory levels:

View attachment 161873 View attachment 161874

Yes, I did call around and there is no inventory in the US or Germany. Naperville says it is not discontinued, but none is available at this point in time. I spoke with Michael at MBCC, but it’s NLA

 

[Seangbadee]

Yes, I did call around and there is no inventory in the US or Germany. Naperville says it is not discontinued, but none is available at this point in time. I spoke with Michael at MBCC, but it’s NLA

I’ll have to use a Kaehler branded one l

 

[gsxr]

Yes, I did call around and there is no inventory in the US or Germany. Naperville says it is not discontinued, but none is available at this point in time. I spoke with Michael at MBCC, but it’s NLA

CRAP. It's good news that they are not yet showing discontinued (meaning NLA), but bad news there's no current inventory. This means there is a decent chance of additional inventory coming in ± a few months. If MB had none on the way, it would have been flagged as discontinued / NLA in Paragon. We'll need to keep an eye on this and see if some become available this spring.

 

[Seangbadee]

CRAP. Its good news that they are not yet showing discontinued (meaning NLA), but bad news theres no current inventory. This means there is a decent chance of additional inventory coming in ± a few months. If MB had none on the way, it would have been flagged as discontinued / NLA in Paragon. Well need to keep an eye on this and see if some become available this spring.

I installed an aftermarket blower motor regulator, and the blower is working again on high, auto,and low speeds. I will wait until the Kaehler unit arrives, and install it with the new Behr blower motor.

 

[Seangbadee]

I installed an aftermarket blower motor regulator, and the blower is working again on high, auto,and low speeds. I will wait until the Kaehler unit arrives, and install it with the new Behr blower motor.

Thanks. Dave.

 

[RicardoD]

I just want to complain and swear $%&**$#@ because my blower motor is not working! AFTER @Jlaa and I recently changed out the blower motor and regular regulator from KAE. Hoping its the fuse or not getting 12V to the regulator. Stay tuned.

 

[Jlaa]

I just want to complain and swear $%&**$#@ because my blower motor is not working! AFTER @Jlaa and I recently changed out the blower motor and regular from KAE. Hoping its the fuse or not getting 12V to the regulator. Stay tuned.

Perhaps Check Fuse F15 and see if it gets +12V from the ignition switch if the fuse is ok:

 

[nocfn]

strip fuse, if thats a check voltage from the PBU to be sure it exists. Funny thing happened to me, the damn lead vibrated off I Shi# you not. pinch them on the spade a touch as a precaution. I hope it is a simple as that ..... keep us updated.

 

[gerryvz]

I am not and have never been a fan of KAEhler components. Hoping it isn't the regulator.

 

[RicardoD]

Wiggling the ignition switch a bit brought the fan back to life. So I think my fuse and KAE regulator are fine. Seems like classic symptom of bad ignition switch.

 

[gsxr]

Wiggling the ignition switch a bit brought the fan back to life. So I think my fuse and KAE regulator are fine. Seems like classic symptom of bad ignition switch.

Cool! But also a bummer about the ignition switch. You may be able to repeat the failure by turning the switch towards the 'start' position after the starter has been engaged (either with or without engine running). It may stop the blower when turning CW, and then the blower comes to life when you turn the key sliiiightly CCW.

I need to replace the ignition switch on my car as well... have had the new switch sitting around for years. Maybe I'll wait for the Ricardo+Jlaa HOW-TO thread!

 

[RicardoD]

Kudos to this W124 YouTuber, for showing me a video of how to change an ignition switch (to fix his fan blower issues!). I already changed my tumbler with new key and that is fine. Expect a proper 500eboard HOW-TO in a few weeks.

Moderator edit: Skip to 7:00 to 10:00 for the juicy bits showing R&R.

Oh and Uncle Kent has a video on ignition switch components and how he hates them

 

[gsxr]

This post from Jon may help a little as well. Now I need to watch those videos...

[Edit: Both videos were helpful, although Uncle Kent's vid was short on content, he doesn't explain how to avoid bricking the lock mechanism/assembly - which is a serious concern.]

 

[nocfn]

Looking forward to your HOW-TO Ricardo.

 

[sheward]

My squeaking blower motor finally failed on the way home from my latest trip. I was lucky to have nice weather after it gave out. I did learn that raising the sunroof pulls a small amount of cool air thru the ducts at speed. If anyone is suffering with the squealing motor, I also found that using the recirculation mode would generally stop the noise.

I've read thru all 5 pertinent threads on the motor and would appreciate it greatly if someone has purchasing info on the Behr unit. FCP has the VDO unit for about $150.00 for knowledge's sake although I'm not looking to save nickels, just wanting to get a Behr unit ordered. I bought the OEM regulator in June of 2021 in anticipation of the job so all set there. Thanks in advance.

 

[dionphaneuf]

@sheward I'm a bit late to the party on this but it looks like FCP has the Behr unit in stock. I grabbed one just now, fingers crossed the order actually fulfills. For some reason they don't list applicability to the 500E, but they do show the 94 E500 (incorrectly, unless car lacks cabin air filter) - maybe that's why you couldn't find it earlier?

Mercedes HVAC Blower Motor - Mahle Behr AB252000P

Mercedes HVAC Blower Motor - Mahle Behr AB252000P

www.fcpeuro.com

Have others tried any other versions of the early blower? Everywhere else I look is either Conti/VDO (not awesome per @Jlaa , not sure if others have tried), or ACM. RM has the latter for $65 only...seems too cheap to be a quality unit.

Mercedes-Benz Blower Motor Assembly - For Climate Control 0008308208 - ACM O.E.M

 

[gsxr]

I'd stick with Behr, despite being USA/Canada and of unknown longevity (the German-made pre-facelift blowers appear to be gone forever).

I'd avoid the "ACM Germany" unit, which at $65 has a strong probability of Chinese origin and kwestionable kwality, same as the Chinese VDO and no-name units. FCP lists the ACM as made in Germany but I believe that is 100% wrong. I bet there is no actual COO on the unit, box, or label.

 

[dionphaneuf]

Ahh yes, this is why I don't normally use FCP Euro....

 

[gsxr]

Ahh yes, this is why I don't normally use FCP Euro....

Yeah... their cart tries to scare you into upgrading. Actual delivery time depends on your distance from their warehouse, assuming it's an in-stock item. More discussion on FCP here, read post #'s 20 to 30 or so.

I generally expect delivery to be 7-10 days and it's usually less than 1 week, even with the free Donkey Post option.