I thought it was my heater switch at first, but I replaced it, because it would come on on High, but then nothing on the lower speeds. Awhile before that it would go on the lower speeds, but not on High. Now it seems to have quit altogether, is there somewhere else I should be looking? I checked the fuses under the hood, and they all seem okay.

 

Right next to the heater blower motor, there is a multi-wire plug. That is a resistor that creates the lower speeds. Often times it burns out, leaving you with only high speed. Some times it overheats and melts the plug. Both of these are symptoms of excessive amp draw caused by bad bearings in the blower motor. You can just replace the resistor, but it if happens again soon, replace the blower motor as well.

The blower motor is underneath or behind the glove box.

 

Okay, I pulled the glove box out, so which of these doo-dads is the one I need to replace?


Grand Cherokee behind the glovebox

 

Sorry, but none of the above. The blower housing is on the bottom of that air box and the resistor is next to it so the element is cooled by air flow. It should be mounted with 2 phillips screws next to the motor. It looks like a plate with 2 screws and a connector.

 

yep, that was the problem and it fixed it

For others, what you're looking for is a plate about 2 inches long and 1 inch wide with a connector close to one end, two phillips screws in the end of the plate, and then it unscrews and comes out and there's a big white block behind it, which is the resistor. You need a bigger resistor like this because of the current it takes to run the heater system.