Intermittent COMPLETE electrical failure!

[Joho]

HI all, I'm new here but I would certainly appreciate some advice. Our 2000 GMC Yukon XL (1500) was running fine over the past several months. Last month I had to replace the battery and alternator right before a cross-country trip, mostly just to be on the safe side. The battery was dying slowly. It's been running fine since, up until last night.

Last night we started it up and it ran sorta normal for about 10 seconds. It wasn't running perfect... almost like it couldn't quite get the RPMs upto idle. It's done this (rarely) before, but is fine after restarting. But this time, it didn't just stall, and sit there with all the lights on, waiting for me to restart it. Instead, EVERYTHING electrical went off. Just like you pulled the battery cable off. I shook the battery and cables to no avail. Suddenly everything came back on. So, we get back in the car, and everything seems normal as I turn on the ignition. The fuel pump comes on, all the lights, the headlights, etc. As soon as I try to turn it over and the starter relay kicks on, everything TOTALLY blacks out again. After a while, the power came back on again! THis cycle repeated several times.

I was jiggling wires, but that really didn't seem to be what restored the power. It was almost like there was some thermal circuit breaker that was tripped, then as it cooled it came back to life. However, I know of no such device on this vehicle.

I don't have much time to mess with this, and I gotta get it out of the parking lot pretty soon. Any suggestions?

Thanks,
John

 

[Vette66]

Not on my Yukon but on my Ford Taurus had the same issue. No visible corrosion, cleaned all terminals really good. Worked great for a while then complete shut down.

Ended up as a last attempt replacing both positive and negative cables. Opened them up after replacing them and sure enough tons of corrosion. Car was from Pa and I guess with salt and whatever it got into the strands on the cables and corroded them.

Outside was perfect looking inside looked like it was sitting the the ocean for years. That was 10k miles ago.

 

[Joho]

Thanks for the input. You were pretty close to identifying the problem. I managed to fix it over the weekend and discovered the following.

First, the electrical problem was just loose connectors on the battery. Now, don't get me wrong, they weren't obviously loose. They were, in fact, snug. So you would think by shaking the wires you would see the electrical come on and off. But that did not happen. Once I tightened them securely, everything worked fine.

Now the question was WHY they loosened. I found that the battery clamp-down doohickey (that plastic trapezoid shaped thing) was loose. This allowed the battery to shift around during driving. We live on a dirt road, so it could have shifted around a decent amount. This motion must have loosened the connections on the cables. The clamp doohickey was loose because the bolt was rusted and basically stripped. So I re-drilled the hole in the battery base, re-tapped it, and put in a fresh bolt. Now that it tightens down again properly, I feel fairly confident this problem won't occur again.

Hopefully this may help someone in the future. The good news is that it's a free fix.

John

 

[ccapehartusarmyINF.(ret)]

this happened to me after i replaced my batterry and put a whole new car stereo ssystem in and i finally figured out i forgot to tighten the battery terminal