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".