How do you diagnose charging system trouble?

[Narnian]

My battery keeps dying after I go anywhere. I've been carrying my portable jump starter, but it's only good for three or four jumps before it runs out of juice. It's gotten to where I can't park the Jeep without giving it a jump.

I don't think it's the alternator or the battery. The alternator is only 6 months old. In fact, I think I replaced the old alternator as a solution to this problem. I replaced the battery last summer, which is when I had the first inklings of this problem.

My first steps towards diagnosis:
I parked the Cherry in the back yard, hooked up a battery charger and checked the meter - 65%. I let it charge for two hours, then disconnected it. I let it sit for 24 hours, then hooked up the charger meter to the battery. 100% charge reading, so I don't think something is draining the power as it sits.

What do I check next?

I have a suspicion that some power accessory is broken and draining gobs of energy whenever the jeep is running, but I have no idea how to check that. I wanted to look for horses before Zebras though. So outside of checking the tightness of wires, what do I look for first.

[The Anti-Chrysler]

Just because your alternator is somewhat new, don't suspect it's good. Test the voltage output. If you're really not getting a discharge from some circuit, then I would guess the alternator, if you've tested the battery.

Other than that, there are some items which may be taking a large amp draw, but it's doubtful they would overcome the alternator so much it would be dead. The only high amp draw items possibly malfunstioing on your rig I would think could be suspect would be:

The wiper motor
The tailgate window motor
Rear defroster
Power window motors

Try taking out fuses, and using an ammeter between the ports to test the circuits with the ignition "on".

[Narnian]

I HAVE noticed one fuse that seems to keep blowing every other trip I take - it's the one labeled BU.

[andy d]

my dead battery gremlin,i solved (i think) by taking the rear t/g window switch out of the circuit. anyway, it hasnt returned since i did. along the way i got the dome light working,except for the r/f door and i taped the lead to that. but all this work was was done after i proved that the charging system was ok with a voltmeter

[oddfire]

another suspect may be the cruise control switch if applicable.................phil

[TexasJ10]

Narian, I think that fuse labled B/U is to your backup lights and the seatbelt warning light. Maybe you pinched a wire in your seat belt sensor. On my truck it is easy to disconnect it near the point where the seat belt bolts to the floor on the drivers side. Just a thought.

[Narnian]

1) I have a cruise control switch, but no cruise control components. Not sure what I'd need to check.

2) I'll go take a look at the seat belt sensor. That would make sense since I generally have junk piled up against the seat belt roller.

[Millerluck]

Will it stay running if you pull the positive battery cable?

I just replaced my Alt a few weeks ago because it was not charging enofe to run without the battery hooked up.

Well it started to do it again after I got the engine put back together(bad cam and lifters).

I found the plug with the 2 wires that snaps into the Alt had a broken tab inside it. Seems it wasn't getting the signal that it needed to be charging. I only found it from pushing on it and the RPM's droped. Letting me know hey its doing somthing now. :D

A trip to the hardware for some blade conectors fixed it up for now. Next trip to a junk yard I'll snag a good plug.

Worth checking.

Later

Larry Miller

[andy d]

the plug with pigtails is available from napa for about 3$