A short? Bad battery? Alternator problem?

[jadek]

We have a '94 Cherokee that recently began having electrical problems. My husband drove it to work today, now it won't start. Hoping you guys might have some advice.

Here are the details: Thursday while driving down the expressway the power door locks unlocked all on their own. I tried to re-lock them, and they "clicked" in all the doors, but wouldn't actually lock. Jiggled the switch several times. A few miles later, they locked themselves, then unlocked, and locked again. Turned off Jeep, tried restarting it (cranked over very hard, like it does in the winter when it's REALLY cold), same thing still went on with the locks. Driver's door and passenger's door switches both do the same thing. Later noticed the locks had unlocked themselves (after being manually locked) while the Jeep was turned off & parked.

Next day, Jeep turned over very hard, the dome light was out, and power locks were still working intermitently and on their own. Radio and clock settings were now lost every time Jeep was turned off. One time very briefly while driving, the battery guage dropped from about 14 to 10, immediately went back up to 14, whole Jeep seemed to "dim" with the drop, but whole incident took less than 3 seconds and drove normally after that.

Later noticed the fuses for the dome light & power locks are blown, replaced them.

This morning, Jeep cranked over very hard, dome light now worked, still no power locks, though. Now, Jeep won't turn over at all, but dome light is nice and bright (not dim like with a dead battery).

One note: Jeep was in the body shop about two weeks ago to get a new hinge put in on the driver's side, so I assume the door was removed (maybe wires got broken?).

Any ideas or need more details? Thanks.

[fredjacksonsan]

With all that going on, there is something funky in the electricals.

If the problems were not there before you took it to the body shop, I'd suspect that something the body shop did has pinched wires or caused an intermittent short. You may want to take it back to the shop and tell them to fix it, or maybe take a look at the wiring in the door yourself.

Electrical shorts can cause all sorts of weird stuff.

[jdl]

I happened to see a service bulletin on a problem like this. It had to do with the wiring harness in the driver side foot well.

Problem with windows/door locks/mirror and or blowing the fuse in the 9 or 13 position in the fuse block.

Remove the lower B-pillar panel and pull back the carpet, inspect the cross-body harness. If any wear is indicated, proceed with the repair. The repair is just wrapping some insulated tubing around the wiring harness, of course if you see a problem with an individual wire, fix that first. That harness may not be your problem, I just happened to see that bulletin.

[jadek]

In regards to the previous post, power windows haven't been a problem at all. Body shop guy is a trusted friend from church, he doesn't think he can fix it.

We ended up getting it towed to the mechanic because it wouldn't start at all. Tried giving it a jump, also tried rolling it forward in neutral, no effect. Could hear a single "click" coming from under the hood when key was turned, and heard the fuel pump "whirring" like it does, but nothing else. Door buzzers & dome lights were loud & bright.

Here is what the mechanic said: does this make sense to you guys? He said the starter & battery are both bad, and it needs new battery ends (they look mildly corroded). He said we have 12 amps to the door locks & power from there to the relay; he's trying to narrow down whether the relay is bad or if it's a short after the relay.

We don't have an estimate yet, but we'd like to keep the cost down as much as possible (is there anyone who likes a pricey fix?) because we finally had to replace much of the cooling system on our other Jeep last week. (It leaked coolant for the past 4 years, and lately got bad enough that topping off the reservoir was becoming a daily activity. I digress.)

I'd like to know if these things are likely to go bad at the same time, and how involved replacing the starter & battery ends can be. Thanks for your time & advice.

[fredjacksonsan]

I've seen corroded battery cables cause some problems, and would replace those first, along with the battery. If they're badly corroded they might not be able to transmit enough power to get the starter moving.

After they've been replaced, I'd bet that your starter will be fine.

[jadek]

Thanks. I'd like to ask the mechanic why he thinks the starter is bad. What should he have done to check that?

[fredjacksonsan]

He probably checked the voltage to the starter, saw it had 12, and concluded it was bad. He might not have checked the amps going to the starter, which I believe is what a corroded cable would stop from getting there. Amps are the capacity to do work, and your starter does pull a lot of them.

Better to replace the battery and cables first, save yourself some $$. You can always have the starter replaced later, if the problem isn't taken care of when the other stuff is replaced.

[jadek]

Thanks, again.

[fredjacksonsan]

Sure thing! Let us know how it comes out.

[jadek]

I'm going to take your advice & do the battery & cables, then see how it goes from there. Will post an update when we find out more.

[citizen@large]

Updates are great! Please do... Thanks!

[jadek]

Okay, the mechanic said he put a new battery & cables in, and the starter still won't do anything. He hooked up a charger to the system along with the new battery & tried again. He said the starter is drawing more juice than he can pump into it. (The old battery wouldn't accept a charge anymore.)
As far as the door locks go, there are 12 amps to the driver's switch, and 6 amps when you engage the driver's switch. He plans to unhook the power to each door lock then hook them back up one at a time to see if he can figure out which one is the problem. I told him the rear passenger door doesn't always lock/unlock unless you do it manually.

[jadek]

An update: the Jeep is running fine with its new starter & battery, but we are living with manual locks for a bit.

The bundle of wires that runs under the carpet by the driver's seat was worn completely through (all 16 of them). Those were replaced, but that didn't fix the problem.

The mechanic wants it back for another hour to finish finding & fixing the problem, but with $1k in auto repairs over the past two months, we are going to hold off on the door locks for a bit. Thanks for your interest & advice; you guys are great.