[Jabo]

When I turnthe heater on I can see the volts drop on the gauge from 14 to right aroun what I think is 10 volts.It varries from the speed detting of the fan is this normal or is there a problem.

 

[xtreme velocity]

I had a 88 blazer that did the same. the heater drew alot of power for some reason. Not sure if its the same for cherokees or not.

 

[Kyle]

Pretty normal, might be a bit low but I would just keep driving it unless it gets worse.

 

[2000XJ]

May want to check the tension on the serpentine belt. When they loosen up a bit, you'll see your voltage drop. It's normal for it to drop with the heater, but not that much.

The serpentine belt has to be pretty tight on these engines, and if it isn't you'll notice your voltage drop when powering accessories, as well as terrible screeching noises from the engine with increased throttle and accessories on.