Adam Bucy

My 99 cherokee sport is overcharging and boiling my battery. I tested it with a multimeter and it reads 19v. I tried putting another pcm from a junk yard jeep and still does the same thing. I tested my pcm on my buddy's 99 and the voltage regulator seems to be working fine only putting 14v to the battery in his jeep. I recently replaced my alternater because it had burned out. The new alternater tests and runs fine. I just don't know what to check now.

erykv1

are you throwing a CEL for anything?
if your battery temp sensor is wonky it could be telling the PCM to over-charge. double check your alternator first.

Adam Bucy

I'm not sure what you mean by "throwing a CEL"

tjwalker

Your alternator, yes even though you replaced it recently, is still the primary suspect.

Bench testing at a parts store of alternators is often inconclusive. The alternator can test fine but be faulty.

I'd replace the alternator; hopefully it's still under warranty.

Rogue4x4

Definitely check the temp sensor...it has a direct effect on the signal to the pcm that regulates voltage. Also you stated your battery is reading 19v but what does the battery read on its own,without the vehicle running?
Check Engine Light

Adam Bucy

It reads 12v when it's not running

frustratedjeep

I had the same problem with overcharging. Plus the engine would run very badly while the Alt was hooked up. I ended up buying a new PCM to correct the problem.

I, however, also lost my power windows and my gauges go dead after about 5 seconds of the key being turned on. I only get that much after I disconnect the battery. So if anyone has some insight on that???........

BlueRidgeMark

A new thread would be a good idea.