Classic2000

ok so ive done a lot of searching and haven't found anything that is what is happening with my 2000 Jeep Cherokee Classic 4.0L. The problem i am having is that once the heater/AC is one and the radio then the jeep become undervoltaged (around 10v) and it screems like a mad man. when i turn the heater/ac off or the radio, the noise stops and the voltage goes back to 14. Also, if it happens while i'm driving, often times the problem will stop randomly and work fine. However, at these times the heater is not hot and the A/c is not really cold either. I've checked the battery and it is good(12.4v) and when the jeep is on im getting around 14.47v. Im out of ideas on what could be the cause. Please Help!!!!!!!

sorry for the long post but this problem is driving me crazy!!

Skb2706

Loose belt...thus the screaming ?? or alternator bearing going bad ?

tjwalker

I agree that the first thing that needs to be ruled out is the belt.

Inspect it. If it is glazed, replace it. If it's old, replace it. The belt on the 4.0 needs to be pretty darn tight to stay quiet. If you do replace it, I recommend the Good Year Gatorback; great belt. With any new belt, I generally have had to tighten it after I've driven the XJ for a day or so. They can stretch a tiny bit.

Classic2000

ok so i checked the belt tension and it is pretty tight. sitting at about 192 ftlbs. I am suspicious that it could be the voltage regulator or i guess the pcm since its in the computer and not the alternator (i think). but i dont know much about that though....