98 GTP blower motor issues

[SsHaDyGt]

Hi All,

The plastic casing on the wires for my blower motor melted and were touching causing the blower to stop working. I separated them and taped them up. The motor is working now but.

I have the automatic dual zone climate control, when I hit auto no matter what temperature it is set to, the motor gradually ramps down and shuts off in about 60 seconds.

I'm wondering with these symptoms if maybe the resistor has gone bad? The motor does seem to work when manually set to lower speeds but it seems that they should be more powerful than they are.

Any thoughts?

[aleekat]

The wires melted for a reason. My guess your motor is going bad and pulled too much current.

[SsHaDyGt]

Yes I agree, the motor seems to work fine but maybe it is drawing too much current. Would the resistor cause this or is it more likely the motor?

[DrRadar]

I've attached the blower schematic from the service manual for your reference. I agree with aleekat that an overcurrent condition probably melted the insulation on the wires.

So what caused the overcurrent condition? As aleekat suggested, the motor itself may be failing. Motors consist of a bunch of low resistance wires wrapped around magnetic material. When the motor is not spinning, it will draw lots of current; the current is reduced when the motor gets up to speed because of "back emf" - a reverse voltage induced by the alternating magnetic current. The wire loops (and magnetic layers) are insulated with lamination material. If "holes" appear in that material, electrical or magnetic shorts can be created that cause overcurrent as well as reduced motor speed. You could possibly check the motor by connecting its leads to battery and ground (preferably through a switch) with an ammeter inline; measure the current when running and compare to the spec. (I probably wouldn't go to that much trouble.)

The "resistor" I learned is not simply a resistor in the automatic climate control as indicated in the schematic. It's the "blower motor control module" and a replacement costs ~$115 at RockAuto. Its output is a PWM signal which would be hard to verify without an oscilloscope. Its input from the A/C controller appears to be a DC voltage level, but I'm not positive about that.

Click here for a thread with information on diagnostics for the auto climate controller which you may find useful.

I've had problems with that same a/c system, including the blower motor and flaky blend doors/actuators. I put in a third party blower motor which has never moved enough air...if I replaced the motor again, I would likely go with original equipment. I still have occasions where the blower motor runs but no air out of any orifice (dash vent, floor vents, defrost vents) that I can tell...haven't isolated the problem but if I turn it off for a few minutes then back on, it usually resumes proper operation.

Good luck.

[Tech II]

If the plastic connector of the harness melted, this was probably caused by too much clearance between the male and female connectors of the harness and motor.....if the wires melted together, it should have blown the fuse....

When this system is in auto, the speed of the motor will vary according what you have the temp set at, and also what the actual temp of the car is.....

GM confused a lot of people, by using that 60-90 scale....people tend to think of it as a thermostat...it is in a sense, but not really with those values.....

Think about it....you set the display for 75(midrange) on auto.....in the cold of winter, do you think 75 will be warm, like your home thermostat? If you had the old slider lever in the cars of the past, would you have it in the middle on a cold winter day, or would you have it all the way to the right?

Same with auto temp....you jack that baby up to 90 in auto.....with that set at 90, it forces that blower to run at high speed all the time....when it gets too hot, manually lower the blower speed....that takes it out of auto....