More 87 300D blower motor

[Finster]

The saga with the blower motor goes on...

Doggonit I wish I was an electrical wizard.

I had a bad blower motor and replaced it. The new motor didn't work. I posted a thread and many helpful responses flowed in. Much thanks. I changed the climate control unit and blower regulator with salvaged ones. Eventually, I got the blower motor to consistently run. However, the motor runs continuously. The fan speed is medium speed only. The fan speed buttons do not regulate fan speed. The fan off button does not stop the fan. Any thoughts folks? I tried each climate control unit in hopes of isolating the problem, but each work identical here. So in short, the blower motor runs continuously on medium speed and does not shut off.

Also, prior to the blower motor going kaput, I replaced the monovalve because regardless of where the temp wheel was set, only super hot air was blowing out the vents. The new monovalve has not fixed that problem.

Sage advice is requested...

[psfred]

Lots of things to check! First, unplug the aux. heater pump (under the intake manifold on that car, hard to find) since a dead aux pump draws too much current and the pushbutton unit will keep shutting things off (this can cause too much heat, too). If that doesn't fix it, pull the right side connector off the pushbutton unit and check the temperature sensors:

pin 10 is ground, pin 7 is the heater core (should be around 8k ohm at room temp), pin 4 is the evaporator temp sensor (same as heater core), pin 2 is the interior air temp (same as above), pin 9 is the exterior temp sensor (about 2.5k ohm at room temp) and pin 8 is the coolant temp sensor, should be about 8K ohm I think, but not sure, there are two different ones.

On my "new" 300D, I got only minimum speed blower and no AC compressor -- turned out that the wires were broken for the engine temp sensor (remember, low speed only fan with cold coolant, and no AC with an engine below 32F). Also have a bad evap. sensor (reading quite hot).

Replace any bad ones (the wires are usually in poor condition at the engine coolant temp sensor, it's on the upper radiator hose nipple).

If you still don't get high blower speed, check the output to the speed controller in the air box -- should be 2 V on low, variable on auto, and 6V on high. If it is, the controller is shot, replace it.

Peter

[babymog]

The aux pump is under the washer bottle.
Great info Peter, I'll be filing it for future reference, thanks.