Eating Alternators
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From: Saratoga, NY
Eating Alternators
Ok here the deal, my 77 F-100 with a 69 351W swapped in has decided to eat alternators. I drove the truck to work the other day for the first time in a few months and when I got it there the battery volts had dropped to about 10 volts. The alt was about a year old with maybe 800 miles on it. I went ahead and bought another one and it fixed the problem. As I was driving home (30 miles) I smelled hot plastic or wires burning 
but it eventually went away. So today I needed to make a short trip down the road just to have that smell again and the battery again drop to 10 volts, and almost didn't make it home. So what I wonder is any of you guys had a similar problem? I wonder if it is the regulator, it's about as year old too but have no idea whats causing this......yet.
but it eventually went away. So today I needed to make a short trip down the road just to have that smell again and the battery again drop to 10 volts, and almost didn't make it home. So what I wonder is any of you guys had a similar problem? I wonder if it is the regulator, it's about as year old too but have no idea whats causing this......yet.
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From: Virginia
Check the wiring out related to the alternator to see if you can find any melted plastic or burnt wires. You may also want to check to make sure it's wired correctly. If your truck as a ammeter guage, the following diagram is how it should be wired up. Sometimes during a engine swap, things can get mixed up, especially if the engine came from a vehicle that had an idiot light, which is wired differently at the alt.
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Its not a very likely scenario but if you got this alternator from Autozone or one of those quicky places and it has the built in regulatoror they don't put very good regulators in them. I took mine to a motor shop and he sold me a heavy duty regulator that he warrantied for life. It was only $15 and I installed it myself.
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Ok I need to mention something here, the swap was done sometime before I bought the truck and I bought it in 1998, since that time I have drove it all over the country without any related problem. Last year while I was in school I tested the Alt on the truck and it had a low amp output not to mention the lights were dim during idle. I put a new one in and it fixed the problem, next day I found battery acid all over the battery and tray, seems I had about 17 volts, so the regulator was toast ( the original relay type) and once I replaced that all was good. So about 800 miles later without touching the truck other than an oil change months ago, out of the blue it frys these alts. Does anybody know if these regulators can be tested off the vehicle? They are cheap enough I will probably just go buy one, and check the wires too.
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