brillo

I have an 04 Jeep Grand Cherokee Laredo, just purchased used. In the midst of a long drive in 40 degree weather, my heater and ac stopped blowing. It will still blow very faint cold or warm air, but toggling between low or high settings makes no difference. Any suggestions for a KISS (Keep It Simple Stupid) troubleshooting?

Hymie

I suspect the faint air-flow is due to the air forced through the system due to the forward motion of the vehicle.

I have a 2000 WJ Grand Cherokee, which recently suffered blower problems.

The blower motor is located below the glove box, above the front passenger’s feet. The wiring to the motor and ancillary modules is easily accessible within this area – without dismantling anything.

Set the blower to on (with the ignition on) and give the wires, close to their terminations a gentle push/pull. I found that the wiring loom on my WJ did not have enough slack, this appeared to be causing a poor connection to the motor. I pulled on the loom, to reduce the strain on the motor connection terminals – which appeared to do the trick.

You might be suffering a similar poor connection on your vehicle.

brillo

Well.. I guess it's just my luck..

I managed to get together all of the supplies needed to troubleshoot this problem starting with the fuses, checking the wiring to make sure I was getting power, etc., I turned the key, started the engine, and voila... Working again. It's painfully difficult to troubleshoot when it's working.. I think it might have been an intermittent connection under the glovebox, at least that is what I'm going to say for now. Thanks for the tip.

Hymie

I too suffered the blower motor operating intermittently – if it came on when started, it would generally remain on, but otherwise it would remain off.

I conclusively proved it to be the connection at the motor by wiggling the wires at the motor connection – resulting in the motor switching on/off depending on the wire position.

Unfortunately the wires (terminated at the blower motor) are non-detachable (at the location where the problem appears to be). Therefore you might be lucky and be able to position the wiring where everything is OK – otherwise you might have to replace the blower motor to effect a permanent fix.

Having a non-detachable cable at the motor makes it difficult to measure the voltage at the blower – from my limited poking around in the area, it was not clear where the connector plug to the blower motor is located.

Jescocom

Most likely the plug to the blower resistor is bad. This is a common problem with the 99 -04 Grand Cherokees. In fact Mopar has a kit to repair the plug for under $20. The resister is under Heat/AC duct behind the glove compartment. You can find eveything you need to know about it here:
http://www.wjjeeps.com/blower_motor.htm