FYI HOW-TO: 1994 Facelift Blower Motor Regulator Replacement

[RicardoD]

Moderator update: Changed title to "How To" thread, as the original question morphed into a great step-by-step replacement procedure for facelift models (and, late Euro-spec pre-facelift models with the dust filter).

1994 Facelift Blower Motor Regulator Removal

@nocfn @gsxr

I am in here on a beautiful Sunday with @Jlaa servicing my wiper motor and trying to replace my blower motor & regulator. I have the KAE regulator that doesn't unscrew from the heatsink.

1) How in the F do you remove the factory blower motor regulator heatsink? @Jlaa and I are stuck. Picture below before removing screws.

FYI, I have the KAE regulator where the connector / electrics is NOT removable form the heatsink. Picture to follow.

 

[RicardoD]

Ok, step 1 completed, removal. @Jlaa figured out how to remove the heatsink by twisting from the top and rotating because the "grid mesh" pushes in a bit.

 

[nocfn]

Sorry I didnt direct you both to the thread I posted on this. I have posted almost identical pictures as yours….

 

[RicardoD]

No problem Nocfn, it was great having you on "speed dial" to sort this out. A big THANK YOU to @Jlaa for the wrenching company, conversation, and help to sort this out. We followed @a777fan awesome guide on the facelift blower motor replacement guide.

HOW-TO: Replace W124 Blower Motor & Regulator (1994/1995 Facelift Models) | "HOW-TO" Tutorial Articles

There is already an awesome write up by user ‘makemann’ on how to do this job on a pre-facelift car, but I thought I would attempt to chip in by sharing my experiences on a 1994+ w124, which has a slightly different regulator installation. Note: I did not actually end up replacing the regulator...

www.500eboard.co

I haven't checked recently but I think the facelift (1994) blower motor regulator OEM part is still NLA. That leaves you with the KAE option but it is typical of aftermarket parts in that it is NOT quite a drop in (Nocfn's post reminded me to check the heat seat holes).

You can see the KAE heatsink is thinner than the OEM one (OEM on the right):



That means of couple of things (and trust me @Jlaa and I learned this the hard way)

1) The heatsink screws are M5 x 0.8mm torx head bolts. Who know what the KAE holes are but the for sure are NOT M5 x 0.8. So you need to a) drill the tapped holes deeper (I used a 4mm drill) and then follow up with a M5 x 0.8 tap.





Since the KAE part is not quite dimensionally correct, you also need to do a bit of plastic filing here:



KAE also has crappy crimp quality, thankfully this crimp released when we had to disconnect the fan after a test, and we were able to re-crimp it, so check those crimps.






Several hours later (thanks for your patience @Jlaa ) re-install is complete, but now I need to order new cabin air filters, and some missing bits.



Here is the Proof of Life, my new blower motor fan spinning!!



@Jlaa spent 99% of the time on my car, and then he spent 5 minutes lubricating his wiper shaft with Molykote 33 light after removing the shaft extension cover and stopping the wiper in the vertical position.



@Jlaa car looks amazing as usual and deserves a 500eboard round of applause for helping me out. We are now available at $400/hr as a team to replace your blower motor but I think we can do it in an hour now after learning how to do it all day today! (not including the lunch break where we had fun driving the little BMW Z3)

 

[gsxr]

I haven't checked recently but I think the facelift (1994) blower motor regulator OEM part is still NLA. That leaves you with the KAE option...

Nice work!

FYI, the OE/Genuine regulators are still available new from MB, but not cheap. P/N 124-821-21-51 for facelift only / with dust filter, $410 list, ~$300 discount:

UPDATE: By 2025, the facelift blower regulator 124-821-21-51 is NLA.

https://parts.mbofcovington.com/oem-parts/mercedes-benz-hvac-blower-motor-resistor-1248212151

https://partssearch.mercedes-benz-classic.com/parts/A1248212151


Pre-facelift / sans dust filter is also available OE/Genuine, p/n 124-820-27-10, $470 MSRP as of Dec-2025. The pre-facelift regulator MAY still be available from Mercedes dealers as of Dec-2025 (link)... however, it shows unavailable / NLA at MBCC (link). This indicates a recent NLA (as of mid/late 2025) and once remaining inventory is depleted, these will be permanently NLA.

 

[RicardoD]

My KAE regulator was in my parts stash and I can't remember if I cheaped out back when I ordered it in 2020 ($140 then) or if the OEM regulator was NLA (EDIT: they went NLA for a while in 2020). In retrospect I would advise to go OEM !! you can just put new thermal paste on the connector/electric part and reuse the old heatsink in place. Also, I think my regulator with 190k miles is fine (it was my blower motor that had a dead spot and a slight bearing whine) so I hope I didn't just create a problem that will resurface in a few years. I think we determined the regulator is not a complicated part ...

 

[Jlaa]

@RicardoD - such a pleasure wrenching on your car in the bucolic forest of NorCal. There is little more gratifying for me than doing a job I have done before on my own car several times (repeat jobs bc of f**kups) on a friend’s car because it makes me look like a MUCH more skilled mechanic than I actually am!

Also your tools are awesome. And I covet your drill press, rolling tool cart, etc etc… and the option to “text a @nocfn friend” was invaluable!

 

[dionphaneuf]

I just want to point out the precise relative position of the headlight wipers of @Jlaa 's car. Rumor has it the James Webb Telescope used them as a level datum during all calibrations for its light years long readings. Only The best!

 

[TerryA]

@Jlaa, I don’t need no stinking wipers

Maybe you’ve heard
“It Never Rains in Southern California”

Even if it did I never drive in the rain


Jlaa, Your car looks amazing! Even the perfectly level wipers

 

[a777fan]

I just want to point out the precise relative position of the headlight wipers of @Jlaa 's car. Rumor has it the James Webb Telescope used them as a level datum during all calibrations for its light years long readings. Only The best!

View attachment 146764

Do we think that @Jlaa has aligned the wipers, and then disabled the mechanisim to ensure precise and consistent alignment at all times?

More than once I have caught my wipers in various states of ‘askew’ following operation. UNACCEPTABLE!!!

 

[Jlaa]

Do we think that @Jlaa has aligned the wipers, and then disabled the mechanisim to ensure precise and consistent alignment at all times?

More than once I have caught my wipers in various states of ‘askew’ following operation. UNACCEPTABLE!!!

WHEN DID YOU VULCAN MIND MELD MY BRAIN???? I DO NOT REMEMBER THIS!!!!! Please no more release of proprietary information!!!

 

[nocfn]

Actually, those are not wipers, they are painted on eyelashes/

 

[TimL]

Now, if @Jlaa could only see the light and understand that his trim needs to be black and not golden, just like Bruno Sacco intended

 

[Jlaa]

Now, if @Jlaa could only see the light and understand that his trim needs to be black and not golden, just like Bruno Sacco intended

You keep your black-trim-affliction to yourself good sir! I have no need for such curse or malady!

 

[geraniumtr]

Folks, Just experienced a blower failure on my 2yr. old made in Canada Behr Hella blower motor. Blower stopped working about a week ago. First I checked the fuses for the blower and PBU then swapped out a spare PBU with no change. Thought it might be the ignition switch since my 94 E320 has high mileage ( 291K ).

Pulled off the 3 pin harness from the terminal behind the brake booster and with the ignition on put a test light on the black and red terminal block pins. Got current so that ruled out the ignition switch.

I didn't think it could be the blower motor or regulator as those parts are of recent vintage. Gained access to the blower which was seized. I could not spin the hamster wheels.

The new motor showed up yesterday afternoon and all is good. I was concerned that the seized motor might have damaged the regulator but that wasn't the case fortunately.

FYI, at the moment, both the factory blower ( 124 820 06 08 ) and regulator for face lift cars are not available. My dealer did find a regulator at MB of Ann Arbor in case I needed it. Don't know about the blower motor. I put in another Behr Hella motor from RM European. Interestingly the label on the box showed 2 vendor names, Mahle and Behr. Label also stated "Produced by Behr". COO Canada. However the label on the motor itself said "Made in USA". Not sure where it was manufactured.

Regards,

Peter Weissman

 

[LWB250]

Based on personal experience, when I have one of these two components fail I will typically replace both. It may be overkill on my part, but this isn't a job I want to be terribly proficient at.

Also, if you use the aftermarket regulator, be sure to clean both the heat sink on the regulator and the blower housing well, and use a high quality heat sink grease on it. I buy the stuff that's used on computer CPUs that has aluminum mixed into it for better heat transfer. I've got no proof that it works any better, but it's cheap insurance in my mind. Every BTU of heat I can get out of that regulator is that much longer it will last, I believe.

Dan

 

[null]

KAE also has crappy crimp quality, thankfully this crimp released when we had to disconnect the fan after a test, and we were able to re-crimp it, so check those crimps.

+1
After linking the fan with the regulator, it did not work. So I started debugging what went wrong and while separating wires the crimp just came off.
Desperate times require desperate measures:
I was in a parking lot where I had no external power source or crimp tool, with everything disassembled. I would not trust only compressing crimp with pliers, what if it comes loose again and I need to redo everything…

So I wrapped the crimp with soldering wire, pulled up my cigar lighter and melt it through by heating the crimp head.



This time everything worked like a charm.

Wrapped the connected wires with some additional isolation tape and put things back together

 

[gsxr]

... the OE/Genuine regulators are still available new from MB, but not cheap. P/N 124-821-21-51 for facelift only / with dust filter, $410 list, ~$300 discount:

https://parts.mbofcovington.com/oem-parts/mercedes-benz-hvac-blower-motor-resistor-1248212151

I've noticed a number of parts getting prices reduced by MB USA this year. Perhaps due to the strong dollar vs Euro? I dunno, but the OE regulator for facelift cars is down to $352 list, and as low as $236 at some 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

I'm not finding the KAE aftermarket regulator anywhere now. Possibly NLA?






The facelift OE regulator is now NLA per my dealer parts guy. RevParts websites show it as "Discontinued", but MB Classic has not yet updated the status online as of Oct-2023:
[Edit: MBCC website now shows this as NLA.]

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

And, the KAE facelift regulator is shown as OOS everywhere, with some sites showing NLA.

 

[ditogachechili]

Gentlemen, do any of you have used regulators from Amazon ($50-70) and do they last?
Other options are VEMO or KAE, which one would be preferred and more or less reliable?

My E320 w/cabin filter, started defaulting into Low speed after about 15-20 seconds and can't cope with the heat during hot summer days. It does start in High mode but slows down gradually. Don't think it's a blower motor issue, I think it's the regulator 1248212151

 

[gsxr]

It's likely the regulator. Any of the aftermarket units will be a gamble. Depends if you want to roll the dice.

The other option is to buy the early style, pre-facelift regulator (124-820-27-10), remove it from the large heatsink, and transfer (with new thermal paste) on to your facelift heatsink. Current pricing is about $470 MSRP, ~$350 from discount dealers, still available new.

 

[ditogachechili]

It's likely the regulator. Any of the aftermarket units will be a gamble. Depends if you want to roll the dice.

The other option is to buy the early style, pre-facelift regulator (124-820-27-10), remove it from the large heatsink, and transfer (with new thermal paste) on to your facelift heatsink. Current pricing is about $470 MSRP, ~$350 from discount dealers, still available new.

Thanks for the tip. Did not realize both regulators were screwed in and interchangeable, that opens another option for me a ACM 1248202710 part on AutohausAZ. Will just need new paste and transfer over.

ACM 1248202710, 3701310 Blower Motor Resistor/Regulator; Control Unit - Mercedes | 1248202710A 1248205810 351321061 9094301755

Ensure precise climate control with the ACM O.E.M. Blower Motor Resistor/Regulator (part number 1248202710) for Mercedes E320, 300DT, 300E, E300D, 300D, 300TDT, E500, 300CE, E420, 300TE, and more. This control unit regulates blower motor speed, enhancing passenger comfort.

www.autohausaz.com

 

[gsxr]

Thanks for the tip. Did not realize both regulators were screwed in and interchangeable, that opens another option for me a ACM 1248202710 part on AutohausAZ. Will just need new paste and transfer over.

ACM 1248202710, 3701310 Blower Motor Resistor/Regulator; Control Unit - Mercedes | 1248202710A 1248205810 351321061 9094301755

Ensure precise climate control with the ACM O.E.M. Blower Motor Resistor/Regulator (part number 1248202710) for Mercedes E320, 300DT, 300E, E300D, 300D, 300TDT, E500, 300CE, E420, 300TE, and more. This control unit regulates blower motor speed, enhancing passenger comfort.

www.autohausaz.com

That $40 ACM unit from AHAZ will almost certainly be one of the cheap junk no-name regulators... not any different than VEMO or KAE for $50-$70.

The photo showing a Bosch label is from old stock. As of last year those were long gone (along with a substantial price decrease, from ~$150 down to ~$40).

 

[ditogachechili]

That $40 ACM unit from AHAZ will almost certainly be one of the cheap junk no-name regulators... not any different than VEMO or KAE for $50-$70.

The photo showing a Bosch label is from old stock. As of last year those were long gone (along with a substantial price decrease, from ~$150 down to ~$40).

On a separate note, what is the correct battery for E320 M104 engine? Previous owner installed OEM 0009823108 but it may not be for this car.
Is it normal for OEM battery to die in 5-6 years?

 

[TerryA]

@ditogachechili,
Probably the best battery you can get is a new AGM Battery! As far as I know AGM batteries only carry a 4 year warranty but the one in my car has worked flawlessly for at least 5+ years.

Personally I would find the most powerful one you can fit in the tray. OEM shouldn’t matter much unless your entering it in a Concourse Auto show.

 

[gsxr]

On a separate note, what is the correct battery for E320 M104 engine?

I think the M104 models all came with a Group 48, but you should be able to upgrade to the larger Group 49/H8 if desired.

Previous owner installed OEM 0009823108 but it may not be for this car.

I think that's a Group 48 size.

Is it normal for OEM battery to die in 5-6 years?

Lifespan depends on many factors, but on average, 5-6 years is normal-ish. A frequently-driven car with periodic desulfation maintenance could last 10-12 years or longer. I prefer AGM despite the higher cost.

 

[Bogeyman]

At the risk of being redundant - I've said this before on here - but I have an '07 W211 with the original battery. It was built in June '06 so now having its 19th birthday. I don't know why. I wish my other cars were that way, but of course they aren't...

 

[ditogachechili]

There's a Interstate AGM at Costco for $180, below are the specs. Would this be too powerful given it has 900CCA? Or there's no such thing as too powerful for w124?

 

[gsxr]

There's a Interstate AGM at Costco for $180, below are the specs. Would this be too powerful given it has 900CCA? Or there's no such thing as too powerful for w124?

The extra capacity only helps... there's no downside besides the slightly higher cost.

Also check if your local WalMart has their H8 EverStart AGM, which should have a 4-year warranty and almost identical specs.

More info here, although some may be out of date.

 

[ditogachechili]

Here's an update. Local MB dealer quoted $262 for the AGM battery 001-982-82-08-26. It's a dilemma MB/Varta or whatever it is vs. Interstate.

 

[gsxr]

Here's an update. Local MB dealer quoted $262 for the AGM battery 001-982-82-08-26. It's a dilemma MB/Varta or whatever it is vs. Interstate.

MB dealers typically get their batteries from a local wholesaler (like Interstate) and then apply the MB decals. I don't know if the MB batteries are any different... but I doubt it.

 

[ditogachechili]

Thank you all so much for sharing your thoughts, managed to replace the battery with Interstate AGM and also replaced the blower regulator, finally have cold air on high!!!