Alternator Issues

Wliebhard · Oct 9, 2004

Any ideas? Installed a diesel in my '85, runs awesom! I hooked up a GM style 1 wire job and it charged for about a week, then the alt. stopped charging. It was REALLY hot a couple of days before it went out. I replaced that with the stock alternator, and stock voltage reg. (built into the PCM). That lasted for about a month, now it stopped charging. I checked for blown fuses, voltage drops and burned wires, everthing looks good to go. Any ideas what might cause ant alternator to quit charging? Bad luck? This is getting expensive!! b-(

bluesman17 · Oct 10, 2004

If it was hot it had something to do with the wiring.

Seabronc · Oct 10, 2004

Hope you can return this one under warrenty. Shot gunning it could be a more expensive method of finding out where the problem is than taking it to an auto electric shop. The problem could be almost anything in the charge circuit.

You need to find out what the actual amperage that is being drawn from the alternator and if it is higher the rated amps of the alternator. Most paths have some sort of protection that would blow if it was drawing excessive current. Have you added any high power audio equipment? If so, maybe your current requirement is higher than your alternator can supply or the combined loads exceed the alternators ability to supply it. The alternator should have atleast the ability to supply about 20% more than the maximum demand when you are running the electrical system full bore.

Good luck,

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Seabronc · Oct 10, 2004

When you installed the alternator, did you include a fusable link in the cable from the alternator to the battery +? That is there to protect the alternator. Something wrong with the battery may also be causing it to draw too much durring charge.

Attached is the typical charge diagram, probably not what is on your truck, but it should give you seome idea of the paths.

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Wliebhard · Oct 11, 2004

Thanks guys I'll check it out on one of my days off.

Berlineta_Z · Oct 11, 2004

What condition is your battery in? A battery that doesn't keep charge makes the alternator work harder. Also is there a draw in the electrical system that drains the battery when the motor is off? A good battery should read 12 volts or more and while the alternator is running you should have around 13.5 volts

Wliebhard · Oct 12, 2004

they're both brand new, 870ccra deep cycles. I don'y have a fusable link but will add one (thanks you, Seabronc B) )

hawk2100n · Oct 12, 2004

Could dual batteries possibly have soething to do with it? Remember it takes twice the power to charge up two batteries. just a thought.

Seabronc · Oct 14, 2004

Hawk2100n's comment is valid. I didn't realize that you had two batteries to charge, especially if you are running them down while the engine is off. Then it takes a lot more output from the alternator the support the truck electric plus charge batteries. What size alternator do you have any way? You still need to check the current requirement with your stuff going atleast the way you normally operate. I think that diagram showed the fusable link sizes for a couple of different alternators plus if you can read it, I added the size for a 100 Alternator.

I suspect your alternator is putting out max in trying to keep up with the demand load and that will burn one out in no time. That's why you need to find out what the demand current is and size your alternator accordingly. It may also be trying to support a high resistance short that is adding to the normal demand.

In short, you can keep buying larger and larger alternators and never solve the problem. I strongly suggest taking it to an auto electric shop.

Good luck,

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Wliebhard · Oct 14, 2004

The alt. that's on it was designed to charg 2 batts. but I'm not sure of their size. I wonder if having larger (more cca's) batts. would adversly effect it? Anyway I really appreciate the help, guys and keep 4x'ing!!

Wliebhard · Oct 14, 2004

Also if it helps, here is a pic of my setup. the batt. posts are close but can't touch. And obviously thier 840ccr's :blush: I also keep them charged when the Bronco's not being driven. i hope it's just a freakish failure and the next one is good to go.

tagto138 · Oct 14, 2004

just wondering what pulleys are on the set up. a cummins eng a gm than ford(?) alternator. if you had an alternator for dual batteries it should have worked but if the ratio's on the pulleys are wrong it might be overspeeding the alternator getting it hot than frying it internally. just a thought.

BigNasty · Oct 14, 2004

It can also be typical POS alternators...
I dislike Advance As alternators after having 4 within a years time due to shoddy parts, IE: the internal voltage regulator on every single one went bad quickly as well as one exploding immediately after installation.