OK, here's the issue. 99 Durango. Blower motor sometimes runs full speed, sometimes doesn't run at all, and mostly runs at various degrees of weak. Seems to run best first thing in the morning or right after work when everything is cold.

Finally got around to digging back into the harness for the motor today and checked the voltage. With the engine running it's a nice solid 14.4 volts at all times, whether the blower is running strong or not. (This is all with the selector on the high setting. Changing to other speeds works as expected when the blower is running.)

As much as I was hoping to get away with replacing the resistor, it sounds to me like the motor is shot. Agreed?

Don't have access to a heated place to work at the moment, so I wanted to double check my diagnosis before I dive into pulling the whole dash out in this weather.

 

Look at the resister first. Then start with the blower motor. My guess is the resister.

 

sounds to me like either a loose connection or a bad motor, if the resistor were goign out you would be down at least one speed

 

That was my understanding, too. I do still have all 4 speeds, they're just proportional to however crappy the motor is running at the moment.

I suppose I'll go ahead and buy the replacement motor. At that point I can wait for the current motor to malfunction, then plug the new one in to confirm the diagnosis. That can all be done with just the glove box removed, so I can at least get definite confirmation before I commit to tearing out the dash.

Why doesn't this crap ever happen when it's warm outside?

 

it might happen when its warm out, you just dont use the blower when its warm out, at least i dont, i just open the windows in the summer, so when you notice it is when yhou need it, or when it gets cold