Pin outs or wireing info for the Automatic cliamte control system.
 

After much research into the issue I ran into when my car overheated it looks like part of of the AUtomatic Cliamte control system failed.

For those that missed the original thread the water pump bypass hose ruptured while I was on the Freeway. And the car overheated while I was pulling over. I had turned the interior heater on to full and when I did so the blower fan kicked into high then stopped all together.

I can hear my interior blower fan running at low speed but under no circumstances will it run any faster, since the car over heated.

My fealings are either part of the PBC (push button controler) Fried or there is an issue with the resister pack on the Blower Fan.

Does anyone know the wireing pin out for the Climate control system so I can try and by pass it and manualy kick the blower fan into mid and high range to test if its a Controler issue or resister pack issue?

Or does anyone know how I can manualy bypass the controls for the blower fan?

BTW this is for a 1990 300e 2.6

It would help if we knew what year and model your car is.

In every model I have seen, DEF will kick the fan to max.

Sorry I noticed that and was editing it as both of you replied

Tried hitting Defrost no change in fan speed just stays running at low speed.

FWIW, I don't think any 1990 MB has a resistor pack blower controller. I think IC blower controllers were in vogue by 1990. Could be that the W201 is an exception.

The blower motor has two wires. Put a ground to one and a high current pot or switch to the other to manually control the blower motor. Make sure it spins in the right direction.

You can't easily convert an IC blower control PBU to work with a resistor pack blower controller.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

I just looked at the CD. Sixto is correct. The blower speed signal goes from the PB Unit to the "Electronic Blower Control Unit" - R/W to a connector, then Y to the unit. Then there is a R wire to the blower from the unit, and a BU (blue) back to the unit (which I assume is ground).

So you need to press the various buttons and measure what you get on the R/W wire. If no change, the the PB unit is TU. If it does vary, then it is probably the control unit.

If it's a resistor pack system, one wire sees ground, one wire sees some voltage. If it's an IC controller, one wire sees constant +12V, one wires sees close to +0V at max, close to +12V at min.

It threw me for a loop when I was diagnosing a blower motor problem and neither wire was a solid ground.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

I went back out to the car and checked and it does definetly look like the blower itself is not starting the sound I was hearing was from the AC system when it starts up.

So not sure were the best spot to test would be. Would the over heating coolant have caused a PBC issue or is possible a fuse. I checked the fuses they look good, the issue only started when the car overheated.

There is a seperate fuse for the blower motor, it's not in the main fusebox. It mounts near the left shock tower in an elongated plastic box, looks like a little plastic coffin. Has a strip fuse under the lid, held down by 2 screws.

Gilly