The symptoms you describe are common to most vehicles which use a blower and MOTOR to circulate the air. There could be several reasons, but since the squealing occurs only when either mode is in use suggests that the cause is that the bushings [bearings] in the blower motor are worn and beginning to gall. If this is the cause, it will require replacement of the blower motor.j3h.
You should check the tension on the belts on ur engine. If they don't hve enough tension,the belts will squeal when running accesories such as the heater since it draws alot of power.
The heat shields on the Cherokee models are needed. The floor pans in the Cherokee models are thin and are penetrated by heat very easily. If you have driven one much, you will notice that the drivers and passengers front floor pans get quite warm from the engine heat. This is true with the muffler also. If it is not shielded the floor will get really hot and penetrate into the cab.
Possible problem with the alternator. Could be source of the noise if it's bearing is going out.
You've got trouble with your heater fan - or the motor that turns it. Same fan for both heat and AC.
The Night
Look to the alt. belt. It may squeal under load.
Classic Rides - 2004 Major Appliances Water and Heat was released on: USA: 14 October 2005
F20 10amp RED
because you need a heat shield to keep it from smoking.
yes
Check the vacuum operated valve at the hose going to the heater core.
No, it really reflects heat.