electrical issue in a 2000 GMC jimmy -- is it a blown fuse?
July 23, 2012 8:50 AM   Subscribe

having an issue with a 2000 GMC jimmy -- seemingly electrical or fuse-related.

first and foremost, i'm a total dolt when it comes to this sort of stuff so forgive any cluelessness on my part.

- while driving home from work on friday, all of the lights and gauges on the dash of my girlfriends' 2000 GMC jimmy started flashing wildly for a few seconds (the truck remained running) and then resumed functioning normally.

- yesterday, i carried some things down to her truck with her as she was preparing to leave. as we approached the truck, she tried to remotely unlock the truck using the keychain alarm/lock thing but the truck was entirely unresponsive. after unlocking the truck with the key and trying to use the lock/unlock button inside the truck, we realized that everything was completely dead. she put the key in the ignition and the truck was 100% unresponse -- no engine turnover, no dash lights, nothing.

- figuring i could at least look for some glaring issue with the battery or something (a loose connection, a leak, whatever), i opened the hood. as she tinkered with the key in the ignition, i noticed a faint electrical hum coming from a particular area of the engine which i then realized was the fuse box. as soon as i began to unscrew the fuse box to check out the fuses (again, i was kinda faking my way through it as i know nothing about any of these things), the dash lights and the beeping sound from the ajar driver side door began functioning. perhaps it was a coincidence but it definitely seemed like this was a result of my fidgeting with/jostling the fuse box slightly. all the lights seem to function properly but there is absolutely mechanical turnover from the engine. just some vague/faint electrical ambience (not at all an alarming or "bad" sound to my ears, just a sort of ambience).

- i had a cursory look at the fuse layout and looked over the replacement diagram (there is a replacement panel with spare fuses in the truck), but decided not to go any further until i made this post. we are wondering whether this is related to a blown fuse of some sort, and if so, which one(s) should i replace first to test? i'm hoping we can avoid an expensive tow and diagnostic if it is in fact a fuse problem but again, as a total novice, i have no idea if this could be a fuse issue or what.

does anyone have any insight as to whether it is in fact a blown fuse and if not, what else it could be? thanks a lot, mefi!
posted by austere to Travel & Transportation (3 answers total)
A blown fuse will usually only result in whatever thing/light that is on that particular circuit not working. So, taillight fuse blows, your taillights don't work. Etc.

I'm not a mechanic so please don't take this as a valid diagnosis (only a professional mechanic who is actually looking under the hood with the proper tools can give you that) but it sounds like there's a short in the wiring somewhere. A little bit of exposed wire or something nudging something else it shouldn't be exists somewhere in the entire electrical configuration of the vehicle. And that exposed part is diverting the current from the battery out of the circuit and probably into the frame of the vehicle. That sort of short will drain your battery dead dead dead, and also result in odd responses from various electrical devices in the vehicle.

This is not an easy fix, sadly. It might be a cheap part to replace, but even if it is, finding where that short is may take a mechanic some considerable time. It may also mean having the entire wiring harness removed from the vehicle and replaced. Which is not a cheap part and also takes some considerable time.

It's probably not even really that, though. You should take her Jimmy into a trusted mechanic ASAP for diagnosis.
posted by carsonb at 9:13 AM on July 23, 2012

If it is coming back on it's not a blown fuse. Blown fuses don't repair themselves. It could be that a fuse is not seated properly. You won't hurt anything poking around the fuses to see if any feel loose. Since everything went dead at once, I'd check main fuse between the battery and the electrical system first. Also, check the battery terminals for excessive corrosion or a loose connection. A bad connection there could also cause everything to be dead one minute, and working the next.
posted by COD at 9:15 AM on July 23, 2012

You have what is known as a 'bad ground' and what it actually means is you have a bad connection, most likely in one of the fusible links in the fuse block.

My personal feeling(rant) on this is that you have fallen pray to GM cost cutting. For a very long time now GM cars (and all cars to some extent) have gotten a bad reputation on reliability. It is not that the engineers are incompetent or the product isn't fully developed or even built badly. It is that the damn accountants find a part supplier willing to sell GM an electrical connector for .01 CENT cheaper and the go with that without any thought to quality or fit or repairability and this is the end result. An otherwise fine car (from a functional transportation perspective) that is going to cost a lot to fix because a non technically qualified GM exec decided he wanted the bonus to pay for his aspen trip and this is how he got that bonus. What does he care that you are now without transportation? or that the company that once defined america know-how and pride in workmanship is now considered a laughing stock?

Anyway you fix this by testing continuity and replacing the bad connection. Note that it, while I said connector in the above rant, the same holds true to fuses, wires, solder, etc. And so the failure point could be a lot of different things but most likely it is a bad connection on the main fusible link for the whole car. That is where I would start.
posted by bartonlong at 9:22 AM on July 23, 2012

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