1990 300D 180K miles

My blower motor stopped working a few weeks back. Replaced the motor. Now the motor runs at only one speed, regardless of what setting I use on the AC Control Panel (The "O" button does stop the motor)

I checked the voltages from the 3 wire plug at firewall, above the brake booster. One side has 12V the other side has 6V. The 6V side does not change regardless of what position I use on the AC Control Panel. I replaced the AC Control Panel but there was no change in function and returned the panel.

Both fuses are OK.

Someone please give me some help here. It's pushing 100F and isn't going to stop for the next month.

Thanks for any advice.

Dan

If you are getting 6v at the three wire connector then the blower should be on high. If you push the low blow button the voltage should be below 1v. If the voltage changes, then the blower regutator is probably bad and its located under the blower motor. You can check the output of the regulator, however you will have to expose the blower to check it. The red wire should have battery voltage and the blue wire should have the control.

Are you getting your 6v at the yellow wire ??... if so , unplug the connector so that you can get the reading right from Control panel with reg unplugged.
See if there is variable voltage then..

Thanks for the replies.

All my voltage measurments where, and are at the 3 prong plug. Went out this morning to recheck. Center wire ground (purple w/ white stripe), 12V wire (Brown with black stripe) and 6V wire (brown with green stripe)

Tried every combo of switch and temp positions at the control panel, including "O". The voltages never changed, always 12V on one side and 6V on the other.

When I put in the replacement control panel, I didn't check voltages; I got the same action from the blower, one speed with every combo. Could I have gotten a bad replacement panel?

Thanks for staying with this thread.

Dan

Just an afterthought. A mechanic said something about possibly a bad "relay" (not the resistor). Does that make any sense?

Thanks again,

Dan

Your schematic shows yellow/red/bk at blower control plug on firewall.
I think you are at the wrong plug.

On the back side of the CP plug [inside car, same plug] should be BK/GN for 12v and w/rd for variable...

Is this a 124.128.. 300D turbo 2.5 ???????

No relay , no resistor.
It is a simple transistor regulated circuit.

Thanks for the replies,

My son came back with the camera and I finally was able to take some pics of the plug.

The two attached pictures show the plug I was taking the voltages for the blower motor from.

Did I pick the correct plug?

Thanks,

Dan

Attached Thumbnails

   

Wrong pluig . that is starter /NSS plug

Last time..
3 prong plug above and in back of brake booster , On firewall .. Not the wall between the Master and the engine.. the FIREWALL between the engine compartment and the passenger compartment.... "THE" firewall..

RED/BLK/YL wires.

Forget the Cameras ... get a Flashlight...

Got a flashlight, got the right plug, voltages changed, no fan speed change. Changed out the blower regulator and all is working great.

Many thanks A.D., I'm very grateful for your help.

Dan

My Pleasure .. that plug is tucked way up in there, so I can see why you were having trouble finding it .. flashlight works for that one

Good Job .. you'r hired .
Now you have to tell the next guy