How do I find a wiring problem

iamgnat · 12-09-2008, 01:19 PM

Not sure this right for this forum since it isn't specifically audio related, but it seems like the most logical place since i'm sure others have had to deal with similar issues.

About 2 years ago my factory Alternator and battery got fried. They were about 3 years old at that point and I knew I was running close to the capacity of the factory system anyway. So I replaced them with a deep-cycle battery and a 250AMP alternator (way overkill, but given the pain of replacing the alt in this vehicle). Now two years later my alt is toast again, so I suspect there is a problem somewhere.

So my question is how do I find it?

When I replaced the Alt, I ran new lines for it. It wired as follows:
1) ~2.5 feet of 0g from the Alt to a 200AMP breaker.
2) ~6 feet of 0g from the breaker to the fuse box (the original factory connection for the Alt).
3) Factory 120AMP fuse at the fuse block where the Alt connects.
4) 2 feet of 4g cable from the fuse block to the battery (replaced the factory 8g-ish).
5) 1.5 feet of 0g from the battery to the factory grounding point on the chassis.
6) 1.5 feet of 0g replaced the factory 10g engine ground cable.

The wiring for my Amps and CarPC is:
1) 1 foot of 0g from the battery to fuse block with 60A fuses for each output.
2) ~6 feet of 8g directly to one Amp (~17A draw at peak).
3) ~6 feet of 4g to an unfused distro block in the cabin (~45A at peak).
4) 1 foot of 8g to my second Amp (~14A at peak).
5) 1 foot of 8g to my sub Amp (~22A at peak).
6) 1 foot of 8g to a 20A fuse for the PC power supply (~10A).

Assuming my math is right (risky at best) and not accounting for the factory stereo and amp that were removed, i'm in the neighborhood of 61A over the original spec at peak which I have never run at (or near).

None of the fuses have ever popped, so I know the Alternator has never put out it's full capacity or event close to it. And none of the audio/pc fuses have blown so I know if there is a short it's a minor one.

Anyone have ideas on what I should check and how best to check it to try to find out what is going on? I can't afford to keep replacing alternators with an almost $400 labor charge every year or two (damn Ford made it so you have to remove a wheel, it's axel, and a bunch of other crap just to get to the Alt

).

Thanks,
-dave

P.S. My worklog for doing the wiring for the Alt last time.

Bugbyte · 12-09-2008, 01:41 PM

I couldn't begin to help you diagnose an alternator problem due to wiring. It doesn't sound like it should have burned out from overload.

The other possibility is mechanical. Not knowing how it failed, I'll ask -how did it 'burn out'? If it was replaced improperly, i.e. the belt is too tight or misaligned, it would shorten the life of the bearings in the alternator.

iamgnat · 12-09-2008, 01:47 PM

Quote: Originally Posted by Bugbyte

The other possibility is mechanical. Not knowing how it failed, I'll ask -how did it 'burn out'? If it was replaced improperly, i.e. the belt is too tight or misaligned, it would shorten the life of the bearings in the alternator.

No idea to the cause yet. Once I send it back to the guy that builds them I may have a better idea.

2 weeks ago (before I knew the Alt was failing), I would have said the shop that installed it for me last time was beyond reproach in my mind as far as install issues go. But now that the tech is trying to tell me it's dead because i've overloaded even though i've shown him how that is patently impossible, i'm not so sure that I trust them.

My biggest problem is that to get the Alt rebuilt, it means that the car has to sit for about a week. To get it out of the garage, it would have to be reassembled which means i'd have to pay labor twice

Trying to con a friend into letting me do it and leave it at his place while I wait for the Alt. of course I need it for a trip to FL at the end of the month....

-dave

AudioXtreme · 12-10-2008, 04:35 AM

With that much power from your alternator and the close enclosed quarters, you might look into over heating too. A normal 250 amp alt has oversized cooling fins and such to help keep it cool. If it's a rebuilt alt it might not have enough surface area for proper cooling and causing it to die prematurely. Just my thoughts on the matter.

billmee · 12-10-2008, 06:46 AM

It would be good to know the failure mechanism,
shorted windings?
rectifier? <most likely>
brushes?

Was the 250 a reman?
If so it might have been a in midlife when you got it.

I think you have no choice but to install another, maybe you can place a thermocouple gauge on it and look for a temperture spec from the manufacturer.

One other thought, can you place a dc current clamp on the 0 awg coming off the alt to see what it is putting out under normal operation?

iamgnat · 12-10-2008, 10:12 AM

Quote: Originally Posted by AudioXtreme

If it's a rebuilt alt it might not have enough surface area for proper cooling and causing it to die prematurely.

Nope these are custom built and he has the casings cast for him. I supposed his design could be wrong, but he does enough business and has a good enough following that I wouldn't expect him to be so highly recommended if they were faulty like that.

-dave

iamgnat · 12-10-2008, 10:23 AM

Quote: Originally Posted by billmee

It would be good to know the failure mechanism,
shorted windings?
rectifier? <most likely>
brushes?

No idea yet. I'll be sending it back to him when I replace it (he is sending me a new 200). I know that info will help some. If it isn't too trashed, i'm going to get it repaired so I have it as a spare in the event I can't find the real problem.

Quote:

Was the 250 a reman?

Nope. He builds them new.

Quote:

I think you have no choice but to install another, maybe you can place a thermocouple gauge on it and look for a temperture spec from the manufacturer.

Yeah, that's what i'm doing. Thanks for the idea about the temp gauge though, any recommendations (especially ones that might be easy to connect up to my PC at a later date)?

Quote:

One other thought, can you place a dc current clamp on the 0 awg coming off the alt to see what it is putting out under normal operation

I know the current Alt is fried so there isn't much point in testing it now. What i'm looking for is how to go about testing my lines to make sure there isn't a short and my ground points (especially for the battery and engine) are solid.

Thanks,
-dave

Injector · 12-10-2008, 11:50 AM

is there anything leaking on the alternator?

Injector · 12-10-2008, 11:52 AM

this might help
http://www.misterfixit.com/alterntr.htm

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