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What would a ground fault in an alternator do?


Burnsy

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Was told my alternator has a ground fault....i understand the jargon but what would the result be ? Thanks
 


rubydist

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It would make it not work. Shorting any voltage to ground will make the device not work, sometimes in a spectacular way.
 

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It would make it not work. Shorting any voltage to ground will make the device not work, sometimes in a spectacular way.
Thanks...It's been working ok but I'm gonna get a new one anyways cuz you scared me lol
 

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Big sparks, smoke, burn marks, then no workee.
 

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it could be grounding once you turn the truck off and then drain the battery overnight. i have seen that a few times
 

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Thanks. I don't know squat about electric. I know lawn equipment and Indian artifacts lol.........i picked up a new battery and alternator, putting them in tmrw morning. Appreciate the reply superj
 

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it could be grounding once you turn the truck off and then drain the battery overnight. i have seen that a few times
The shop today, a great local shop , says i have no ground fault and alt is fine....auto parts store had said i had a ground fault.....the mechanic at the shop found my problem.......a draw from engine bay fuse box fuse 1 50amp I/P fuse panel, goes to the cab fuse box, pulling fuses from the cab fuse box tmrw to try to see which one is the culprit drawing it down overnight......i have the 50 amp fuse out now, now that im home for the night, so it doesn't drain overnight.........battery, Alt, cables/connections all good according to mechanic.....Embry & Sons Automotive, great shop, great guys, great prices, Hudson, FL......they also have a great band The Embry Brothers Band check em out!
 
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rubydist

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So technically the auto parts guy appears to have been correct - if you have a parasitic drain, that can accurately be described as a ground fault. A "ground fault" is any time the voltage takes an unplanned path to ground. Typically this is a hard short, but a smaller drain is also technically a ground fault.

But instead of getting hung up on terminology, what we need to do is chase down where that short is located and correct it. In vehicles that are in the range of 20 years old, I have found numerous short circuits and open circuits inside the wiring harness. That is most likely what you have, given the description. The other common situation is that the harness has rubbed bare on some of the metal structure (under the dash is most likely in your situation) and is leaking voltage to ground. The bad news is they are not fun to find, and the good news is that once you find them, they are usually pretty simple to fix.
 

Burnsy

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So technically the auto parts guy appears to have been correct - if you have a parasitic drain, that can accurately be described as a ground fault. A "ground fault" is any time the voltage takes an unplanned path to ground. Typically this is a hard short, but a smaller drain is also technically a ground fault.

But instead of getting hung up on terminology, what we need to do is chase down where that short is located and correct it. In vehicles that are in the range of 20 years old, I have found numerous short circuits and open circuits inside the wiring harness. That is most likely what you have, given the description. The other common situation is that the harness has rubbed bare on some of the metal structure (under the dash is most likely in your situation) and is leaking voltage to ground. The bad news is they are not fun to find, and the good news is that once you find them, they are usually pretty simple to fix.
Thanks.....the alt was off the truck....i took it in to them...........they said they couldn't test it while off the truck bcuz it has a ground fault
 

Burnsy

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i DO have a parasitic drain.....as soon as we find the drain im changing the alt, it's old and the bearings are getting a little noisy, it's charging good but I've never liked the idea of waiting for an alternator to go bad before replacing...ive heard too many bad stories.....age and worn bearings are enough for me to change it and have peace of mind, only $150 and install myself
 

Burnsy

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I kept saying we were gonna isolate my problem "tmrw"....i don't why i kept saying that, we're gonna work on it Thursday....they are swamped until then......i was able to watch a few different YouTube videos and buy a multimeter and replicate the test the mechanic was doing to find my drain........i already know its the 50 amp fuse #1, goes to iside cab fuse panel... from reading up a little i saw to leave the 50 in with meter hooked up and start pulling fuses from the inside cab fuse panel........so the conclusion is the infamous fuse # 26........so far I've determined the battery saver relay, glove box light, and i think door ajar switch and dome light(not sure if its dome light bcuz of battery saver or if dome light manually on spinwheel adjuster, or if its all tied in together...).......does anyone know what else is on fuse 26?.....2001 3.0 auto
 

Burnsy

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So its a few days later,Tues, truck goes in shop thurs....ive learned a little elec the last few days, learned how to somewhat use a multimeter, enough to track my drain to a certain point.....beyond where i am now i know I cannot do/diagnose but I'm ok w that. For me i accomplished a LOT lol......so I had narrowed it to fuse 26.....with fuse 26 IN and draining, I pulled the relays under the dash one at a time looking for the drain on the meter. I found it but im not sure what relay i pulled.....but i don't think it matters bcuz its not the relay itself, it's the wiring/receptacle...........i put the relay that sits beside the "bad" one in that receptacle and IT showed drain also.....that same relay tested good in its normal receptacle, so I know its something with that certain receptacle rather than the relay.........with no relay in the receptacle the wiring and terminal is very loose in the plastic casing so I'm guessing my problem is there but that's just a guess.....i called the shop told him how far i got.....he mentioned maybe a ground for that circuit/terminal etc, and a few other things.....the exciter.....? All i know is ive gone as far as i need to go for myself. I know its nothing disastrous or something that's gonna fry me in the next two days, as I've learned how to manage it........if i go anywhere and park and shut off the truck and i know its gonna sit for more than 30 minutes i just pull fuse 26 after i shut off the motor.....I put the fuse back in right before i start it. Haven't had any no-starts or even close doing it like that so its getting me by til thursday
 

Burnsy

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The shop says my GEM has shorted itself out....they said they unplug the GEM and the drain goes away, they found a used one , gonna install it for $200 monday....325k miles on my truck, may be the original GEM
 

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..i put the relay that sits beside the "bad" one in that receptacle and IT showed drain also.....that same relay tested good in its normal receptacle, so I know its something with that certain receptacle rather than the relay.
I’m curious. Not trying to give you a hard time. But may be able to clear something up for you. Were you pulling “relays”? Or fuses? There is a distinct difference and using the right term can make it easier for us all to communicate.

So a fuse is a device used to prevent too much current from flowing in a circuit. It only has 2 terminals and when too much current flows in the circuit, a small element inside is melts. We often say it “blows”. The fuse is then useless and must be replaced with one of the same current rating.

A relay is basically a switch that is operated by a magnetic coil. Most automotive relays usually have 4 or 5 terminals. 2 terminals are for the “control voltage” that energizes the magnetic coil to operate the switch contacts. The other terminals are where you connect the circuit that is being controlled.
 

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