kommandant

1995 4.0 cherokee.. volt meter reads low ( but not in red ) when I start it... but after 5 or so miles of driving it jumps up to 14. This is pretty consistent.. almost every day.

Battery is less than a year old, reads a little over 12 volts.

Im guessing alternator is failing BUT what gets me is why do I get my charging volts after driving for a bit?

Check engine light is on most of the time when this is going on..got a code 34 ( cruise control circuit )... I dont even have cruise control

Battery/voltage idiot light has never come on

Belt tension seems like it could be tighter but ac runs fine so I dont think its out of spec.

Any ideas gurus? Maaaan I hate electrical issues

Bustedback

No code 41? You should get that code when the alternator field circuit is not switching properly. If you have the original alternator the chances are pretty high that the brushes are getting close to being completely worn out and losing contact.

kommandant

Thanks for taking the time to reply. No code 41 as far as I can tell. I'll try for a new code after driving again.

tjwalker

So am I. I've seen alternators fail in this manner. It may be wounded, but not dead.

*Verify charging system output with a voltmeter on battery. First with stone cold engine and then after running for a bit and when you notice that your voltage has dropped on your gauge. Your gauge is probably not lying to you, but you want to be sure this is a real charging problem and it takes only a few minutes of your time to do so. Got a meter? If no, buy one; they are inexpensive and invaluable to anybody working on their vehicle.

*Freshen engine grounds just to eliminate that as a possibility.

*Double check that code too.

Good luck and keep us posted!

Bustedback

When my alternator failed I was getting a code 41 trouble code. I checked the charging system with my DVOM and had 14.2 volts. Clear the code and drove to work the next day and the check gauges light and check engine light came on, only shows about 8 volts on the gauge. I decided I had enough of that retarded dance and changed the alternator. I inspected the old one and found the brushes were very worn and hanging up so they weren't making contact on the commentator.

kommandant

Well this morning I managed to pull a code 12 ( batt disconnect ) and a 41 but it was charging for half of the drive. On the way home tonight it didnt get to 14 volts at all. Im just gonna pick up a new alternator and belt this friday and hope that solves it.

Thanks for the help folks

tjwalker

If you pulled a 41, and with your symptoms, a new alternator should be the ticket.

Be sure to get the belt properly tightened or you'll get some screeching. May have to snug it up a bit after the belt is run for an hour or two as depending on the quality of belt you bought, they can stretch a tiny bit.