Help? I'm stumped

Hello, I have a 1997 Jeep Grand Cherokee Laredo with the 4.0L engine. Within a minute of starting the car the check gauges light will come on and the voltmeter will drop to zero. The car will operate fine for awhile and then the radio will die. After shutting the car off it won’t start back up right away. The battery still supplies power to the lights, etc but the car will start to turn over and then I get a grinding noise. If I let the car sit for about an hour or two it will start up again. I’ve replaced the starter and the alternator and battery both check out (tested them at Schuck’s). I’ve also replaced the battery cable ends on both the (+) and (-) since they were looking gnarly. Any other ideas? I’d replace the cables but there are other accessory wires connected to them and I’m not sure I can get a straight across replacement.

Thank you.

Look under coating at battery end of red cable for green crud.
Was alt,starter and battery bad when you replaced them?

No green crud, I cleaned the battery posts, cable ends and connections. The alternator and battery weren’t replaced I took them to Schuck’s to have them tested and they were good. The starter was bad when it was replaced. Thanks for the reply.

Check the ground wire between the engine and body.

That checks out OK. I’m assuming you mean the negative cable that attaches to the body above the wheel well? The connection was cleaned and the wire seems to be in good condition. There is a red wire that runs from the alternator to the fusebox and it’s the only positive wire connected to the alternator. If it were faulty could that cause my problem?

Yes. I would remove the fuse block, turn it over and see how it looks underneath…Any signs of a melt-down? This sounds like a bad connection somewhere…

Did you slice the coating 3-4 inches on the red wire looking for crud? If not do it on the side so when you tape it up it will stay drier.
Only other thing I would try is running a ground from battery to the motor.

I stripped the coating at the ends of the cables when I replaced the battery connections and they looked clean. Do you mean the negative ground on the engine because there already is one. It has to be one of the connections from the alternator to the battery right?

Are you saying that the car starts and runs for a while sometimes? Then not others? It is not clear. You said i’ll wait and then the car starts up again nut does that mean you can drive it or not? If you cannot drive the car then you are missing a connection to the alternator. It just is not there. Check the battery positive to body ground with a voltmeter with engine running. then turn on all the power stuff includeing the horn while watching the volts battery positive to ground. With the engine at idle you should see 12.5 volt or better. if not your alternator is not connected right. At 2k rpm the battery positive to body ground sould be 14.5 volts. Tshoot the alternator wire harness since it seems you already checked the battery side.

The car will start and is drivable. If I drive it short distances then there is no problem at all. On trips of >10 miles the radio will die (I assume that if I continued to drive it other accessories would start to die as well) and if I turn the car off at that point it won’t start right away. All I get at that point is the engine trying to turn over and then a grinding noise (I assume from the starter). If I wait a couple hours the car will start right back up again with no problems. It seems like the alternator is not charging the battery when the car is running but the alternator checks out fine. Is the wiring harness on the alternator the group of 4 connections coming off of the negative cable? Does this explanation clarify the problem a little more? It’s an unusual problem. Thank you all for the ideas.

How’s your alternator belt? Are you reusing the belt or did you put a new one in? If it’s slipping, you aren’t charging. New belt and check the tension.

This behavior is one I’ve seen, particularly, on Chrysler products. I think that it’s caused by the design of the gauges electrical control system. Whatever controls the gauges’ electrical supply, is (I feel) to blame for the gauges dieing, and the decay of the other voltages passing through the dash and ignition switch.
An automotive electrics and electronics repair shop might be able to sort this problem out.

I have one serpentine belt and the tension is good, no slipping.

Thanks for all the replies. The problem stopped for awhile after I took the wires off one last time, cleaned them again and replace them, then 2 days ago it started again. I’m thinking it’s time to take it to an electrical repair shop. Thank you all again for the help.

Just to let everyone know, I took the car to an electrical shop and they said that the alternator does not charge under a load. Apparently when I took the alternator to Schuck’s they didn’t do that. My plan is to replace the alternator this weekend and cross my fingers. Thanks again for all the help.

Well, thats your problem…Schucks. Go to a reputable parts store like Napa or an independant and ask them to evaluate your alternator and your battery. They’ll probably wheel out a machine to your car and they will test the battery, alternator, etc. I bet you will find out that the voltage regulator (Inside the alternator) is bad. You could spend months changing out alternators that are guranteed by Schucks. They don’t care how many times you replace their warrantied alternator. There are thousands of stories related to Schucks, Pep Boys, Orielys, etc products. Trust my experience.

This was what I was going to suggest. While I haven’t had it in my Wrangler, my old Caravan had an event that baffled the crap out of me. I knew it was a dash ground. Everything through the ignition switch worked, but nothing else. A “check gauges” light lit up (the only thing working on the dash display). The radio would work (through ignition switch) but the hatch release would not (dash ground).

Now the OP should have a data BUSS that transmits all the input to the gauges. If his volt gauge reads low - the PCM is telling it to indicate it.

This behavior did not indicate a bad alternator. I didn’t see you post ONCE that you recharged your battery. You indicated that you merely let it set for a couple of hours and the condition went away.

If anything I would have thought it a shorted battery. They can operate 24/7 perfectly fine and then produce very strange anomalies.

Norm. He should have no voltage regulator. His PCM should set the frequency of enabling the field windings to produce the proper voltage. He should also have a battery temp sensor in the battery tray. If the last place testing the alternator did it in the vehicle, then I might look at that battery temp sensor. It could prevent the alternator from being triggered often enough. This would also coincidentally probably do exactly what is described IF it was also a shorted battery. Even though a shorted battery is very rare, the time span for the occurrence is not age related. I had 3 go bad in one vehicle. Not one failure occurred beyond 18months.

Thanks for getting back with the final results, fkoski. And although it’s awfully generous of the McParts stores to offer free testing they fall short on having someone knowledgeable to do the testing. Those bench testers with the video control screen are very impressive to the public but severely limited in their ability.