Tony Curtis

Hello!

Our Mercedes 300e blower fan has stopped working. It was intermittent for a day or so and then quit and has a couple times since then come on briefly and stopped.

I have researched all the forums here and done what I thought was the right testing. I purchased the Blower Fan Regulator/Resister.

The tests I have done are these:

I tested the blower fan itself by connecting the battery to it direct with 12 volts. No problem there... it came on and there are no squeals or issues.

I tried hooking up the NEW Blower regulator to the plug behind the brake booster and the leads on the Blower Fan. (I took the blower motor and old regulator out so just doing the test outside the actually compartment without reinstalling it all to test it actually works) -- Nothing works

I tested the plug up behind the brake booster with my voltmeter. With the car on and the blower set to EC and either Low or High or auto.. I get various readings.

However.. what puzzles me is that on the "red" terminal I seem to get no voltage. On the "yellow" terminal I get various voltages depending on the fan speed.

Should I not be getting a constant 12v reading the on the red no matter what?

I'm at a loss... I have also tried banging not the dash and the climate control unit... and also jiggled my ignition and nothing changes there.

Also checked the fuses and I am getting 12v across both ends.

If anyone has some insight that would be amazing!

Plutoe

change the fan regulator and live longer!

Tony Curtis

aaaah... I said I did that. ha ha No change!

Plutoe

Forgetting about your Sammy rigged fan controller----do you get any voltage to the fan controller when fan speed is adjusted?

Tony Curtis

I only get voltage from the YELLOW pin to the regulator. I get no voltage from the RED pin to the voltage regulator. The yellow varies depending on fan settings.

Plutoe

Post your Vin and I will look for the wiring diagram! However sounds like your AC controller is shot.

Tony Curtis

No.. we've isolated it to somewhere between the fuse and the red (#2 pin) on the x64 (3 pin plug) that powers the Fan Regulator. We don't have 12vlts at the pin and there should be.

QVHK

I am not familiar with the W124 Air-con system. However, I have a Jaguar X350 and the blower fan worked intermittently as in your case and it totally died one day. It turned out to be a faulty resistor that controls the on-off, fan speed, etc. The fan and the air-con return to normal after replacing the resistor. However, the W124's ventilation and air-con system might be different.

Tony Curtis

I found the problem! DUH... It WAS the strip fuse. Had a break. I have worked on the car lots and have NEVER noticed that!

Thanks for all your help everyone!

QVHK

Glad to know that you eventually found the problem and fixed it!