1995 W140 Blower Motor issues
 

Blower motor stopped working. Applied 12v direct and it runs full blast. I read several forums and decided to replace the regulator. Blower still does not work. What do I do now? I live in Michigan and it is very cold! Please help!

Maybe the control unit, N22 is bad. . . not producing the reguired 'drive-voltage' as the blower wheel (my car has a 'potentiometer'; your car fan blower control) is advanced. If it's N22, that's rare in my experience.

How do I diagnose / fix?
 

Everything is put back together right now. If I ground the motor to the frame, it runs full blast, so I know that it is getting power.

I'm an electrical goober. I can say that my '97 S320 had it's blower motor regulator replaced under warranty long before I bought it.

Steve

The speed regulation is in the ground leg, if you ground it you bypass the regulator. The control unit could be bad, the control units had a self diagnostic mode see sites
http://www.continentalimports.com/
or Jims site
http://pages.prodigy.net/jforgione/MB_S500.html

Forgot about that!!!! Peter, tnx for the reminder!

Use MENU#15 and check out #8 in the "operational checks". The reading should change as your select different blower speeds.

Automatic Air Conditioner Diagnositc test step 8
 

I am at my wits end! I ran the test and it gives me a reading from 10 to 60 when I adjust the dial.
I am quite confused. Control unit seems to be functioning, replaced blower motor regulator.... Why won't the blower function?
Engine light is on. I ran other DTC tests and came up with the following list of problems:
E006 E073 E074 E075 E082 E083 E086 E087 E102 E103 E106 E107
Could any of these be contributing to my problem?

They certainy are. If all is OK w/ the AC, you should get a "E01", anything else ain't good!

Even have some Aux Fan problems.

What's the code that's causing the CE light??

Suggest you get a readout of all modules in the car with a scanner.

I will check codes with a scanner next weekend -
 

Brother-in-law has one. I willl let you know what I find out
Thanks

I assume you mean that you ground the blu wire and not the motor frame ??

If so, then you want to check the voltage at the yellow wire going to the regulator with key on and defrost position. That is full trigger for the regulator . With voltage there , the reg will complete the blu wire to ground , resulting in full fan.
If no voltage at yellow, Control panel is not sending the trigger to regulator.

Re-read post#8

Post 8 tells you that the CP show trigger voltage at the CP..it does NOT tell you if there is voltage at the yellow wire at the regulator.

The test is to check right at the regulator for 12v from red to blk and trigger voltage from yellow to black.
If he is grounding the blower motors blu wire and that gives full fan, then either the reg. is bad, the reg does not have proper feed , or the reg is not grounded.
Having the CP detect voltage output at the CP does not insure one has voltage at the regulator. Specially considering that he has already changed the reg and grounded the neg side of the blower, getting full blower.
My guess is the reg is not grounded...........but I would do the voltage check at the reg plug first.

How do I do a voltage check at the reg plug?
 

I grounded the blower motors blu wire and that gives full fan
not grounded.

I do not have a voltage meter. I can pick one up, what do you suggest?

Then , where do I hook it up?

If you grounded the blu wire , you have by-passed the regulator circuit and verified blower motor and positive 12v feed... It is the reg that grounds the blu wire [ neg side of the motor/ a switched ground circuit] when the yellow wire gets a voltage sig from the CP.
So, a meter would be nice , or even a test lamp would help.
You are looking for bat voltage [ 12v] at the plug that goes to the regulator.
This will be the feed side of the plug, not the reg side.
This will be the red/blk wires ....
..then you want to see a lower voltage [approx. 6-8 v] at the yellow /blk wires when the key is on and the defrost position is set.

I am assuming you do have the new reg mounted???

True, but it's just one wire and odds are that the blower control voltage is there.

I wonder about the blower *and* the reg. . . . maybe the blower is not installed? Or the blower reg is not mounted on the blower?? That would be too funny. :wacko:

It's not a "switched ground ckt" but rather a transistor action switch. Others may be confused thinking it's a "switch".

Feeder plug
 

I am looking at the plug that goes into the regulator
There are 4 wires:
Red
Brown
Red/Grey
Green/Grey

Red and Brown reads 14.27 v
Red and Green/Grey reads 7.49 v

Did I do this right?

Blower reg IS mounted on the blower
 

This is "Blowing" my mind!

Good one! :wacko:

Just to make sure:
1) do you have the blower mounted in the car??
2) Is the blower reg mounted to the blower??

Blower is mounted in car / regulator is mounted on blower
 

what next?

You know that and I know that.... but I am trying to get to the basics without getting technical on the guy.
OK??

For testing purposes, I want him to know the circuit is controlled/switched ON the GROUND side so he understsnds why the blower works when he grounds the blu wire.
I will let you take it ...

Instead of arguing amongst yourselves- does anyone have a solution to my problem?
 

It is 19 degrees and snowing here.....

Could my new blower reg be bad?
 

How do I test the new blower control unit? Everything seems to be okay until the wires go into that little critter

Actually, the 'switch' is an "analog" variety that is an variable attenuator with the regulator itself as the 'heat-sink'. Energy is either pass through (high speed) or lost in the regulator as heat (low speed).

Hope that's not too technical . . . but it's how the blower reg really operates.

Ok, Eric . . . if all is connected and you have verified that voltage from the N22 unit (in the dash), the blower should be on. The higher you set the voltage from N22, the faster the blower should run.

If all is connected properly, sounds like the reg is bad??

Blower control unit is one week old
 

It is a KAE Blower Control unit purchased from ******** AZ. Instructions say that "the surface of the blower control unit is pretreated with a very efficient proper amount of copper=heat=agent"

It seems like blower regulator is grounded, motor will spin when everything connected and I ground the blue wire. If I unbolt the blower regulator from the blower and ground the blue wire, nothing happens.

Any ideas????

The "stuff" on the bottom is silicone grease; it's a heat conductive paste that gives heat transfer from the reg to the blower's frame. Without this grease the reg will fail quickly.

If the reg was 'operated' without being attached to the blower, it could blow immediately. If it was 'touched' to the blower's frame and run, it could blow.

Since there's a 'connector' for the wires, it's normally a "plug-and-play", especially if the blower worked before this. The reg is a normally high failure rate item b/c of the power it has to dissipate.

I threw an old blower/reg assy out last week; wish I had it to verify what color wire goes where. Other than that, it should 'work'!

Is there any way to test the blower regulator
 

before I order another one?

There probably is a piece of test gear that MB uses but I'm not familiar with it.

I have a "transistor" tester that would tell the basics but it's never been needed since the failure is exactly what you experienced; blower 'barely' operates.

How about your inde?? Maybe he can test it on a similiar car? Actually, you can test it on most S class cars from 1992 to 1999.

Same problem
 

First of all, thanks JimF for your information on A/C checks. They are very informative.
I have a 1995 S320 with 180,000 miles bought used that the blower would slow without cause and finally stopped blowing all together.
All sensor readings appear normal with step 8 going from 8 to 60 with fan speed dial min to max.
There were a couple DTC but I don't know from when they occured, I deleted all back to E000 to see if new codes logged.
It stayed on E000 for 3 days now. Did not show E001. Don't know if that is a problem or not.
I believe next step would be to check red to black and yellow to black voltages on reg.
Any suggestions welcomed.
Thanks again
Murf

I am also having this problem on my 96' S320. I checked with my volt meter using my red lead on the blue wire and my black grounded on th frame. I got between 3 and 4 volts with the car running or off. I must be doin something wrong.

Parked my 97 S500 for 3 days at airport, AC was working.
When I started car the fan was not working. Prior to that the fan seemed to slow from time to time. Since it happened so suddenly I am thinking it is the regulator. How do I test fan?
Thanks

Gain access to the blower compartment

Look at the blower motor and you will see a red and blue wire connected to it. Jumper the BLUE wire to ground (Yes, it will spark!) If the blower is good it will start to run at full speed.

The regulator works by varying resistance to ground, so this test effectively bypasses the regulator. BTW, this test will work with the key on or off because the red wire is hot all the time..

Edit: Found the DIY with pictures: http://www.peachparts.com/Wikka/W140BlowerMotor

Regulators aren't too cheap, but they're an easy DIY to replace.