Pre- 1991 are in alternator not PCM, they were all PCM 1991 and after.

 

Good to know, Thanks! Coach

 

a good test for a dead or crappy alt is to crank it up disconnect that battery if the car dies it needs a new alt

 

What is the "ICA sensor" or the "ASD relay"? Lol, having the same problem. XJ runs fine, voltage drops and stays low enough to create a concern on the problem until the next morning, when you drive to work for 10 minutes and start deccelerate, "voltage drops" again.....

 

I just installed a upgraded 140 amp alternator and heavy gauge cable kit on my 89 Cherokee. Cable goes from alternator to battery. The voltage meter drops to 10-11 after the engine is warm and at idle like at a stop light. When accelerating and driving the volt needle goes back up to 12-14. No problems with dimming lights, etc.
I don't have a clue.
AVjeeper

 

Read here and here.

 

Get a voltmeter and measure the voltage at the battery terminals at idle.
That will tell you if your dash gauge is accurate or maybe your alternator is kaputt.

Only other thing i can think of is a loose slipping belt trying to drive the alternator pulley at idle rpms'.

 

i hear thats dangerous, they say alt needs the batt load, volts could spike? seems like regulator would hold it but i wouldnt try that.

 

You should never disconnect the battery with the engine running on a computer controlled vehicle. The battery acts as a buffer for the alternator. Without the battery, the voltage regulator spikes (ive read as much as 150v) and you run the risk of frying the computer, among other things. And no, the voltage regulator may not be fast enough to stop it.