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?

This is "Blowing" my mind!

Good one!

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

__________________
Regards . . . . JimF
-------------------
'94 S500 Cpe

Visit my Mercedes Web Page

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 ...

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

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??

__________________
Regards . . . . JimF
-------------------
'94 S500 Cpe

Visit my Mercedes Web Page

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'!

__________________
Regards . . . . JimF
-------------------
'94 S500 Cpe

Visit my Mercedes Web Page

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.

__________________
Regards . . . . JimF
-------------------
'94 S500 Cpe

Visit my Mercedes Web Page

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