memoniz

I am about to put in my third alternator in two years. I have a '96 F150 w/300, auto. I did replace the a/c pump 4 months or so ago and had problems with the system and replaced the alt. and battery. I never did replace the diode. Also that alternator was maybe a year old. The previous one I thought just went bad due to age. Right now, the gauge reads on the low end of normal and the light is on. I pulled the positive and it cut out instantly. The gauge doesn't bounce around like it did before, it just starts reading low, and then comes back to normal later as I drive. No power surges, no nothing as if something was sticking and later gets knocked loose. I would like to here any and all possibilities for electrical systems is not my strong suit and have a tendency to rip out and replace.
Thanks.
By the way, the truck has 282k miles and most everything is original in the wiring aspect except the alternator and maybe a relay or two.

broncojunkie

I would check all of the wiring...especially the ground cable. Just because it looks ok at each end doesn't mean it is good. You can use a meter to check ground/continuity. Even a simple light tester might give you an idea. Sounds like you may have a bad alternator or voltage regulator, though. Take it off and have it bench tested at the parts store. You can also purchase a brush set and voltage regulator separately, but in my recent experience, I've found that the vr cost about half as much as a new alternator. Since it is newer, I might even consider keeping the alternator you have instead of turning it in for the core charge. You might use it on down the road (switching voltage regulator, brushes, maybe bearings will go out in the new one, etc).

Oh...and don't pull battery cables while motor is running. Your battery works like a surge protector...absorbing voltage spikes and saving your delicate electronics. Old vehicles, you could do it without hurting anything.

memoniz

I'm going to take the alternator back to Autozone, I bought one with the lifetime warranty and they'll replace it. I've pulled cables on the truck before to check the alternator and found it to always be a reliable test. I'm just trying to figure what the problem could be instead of replacing it every so often. I have replaced the positive cable but not the ground, maybe it's time to do that.
Thanks

broncojunkie

If it's under warranty, then yes, I would exchange it (if it's bad, of course). Not unusual for these aftermarket parts to fail prematurely. I used to replace the fuel pump in my sister's tracker about every 6 months, lol!

I still have to recommend not checking it by pulling the cable, though. It's all fun and games until you melt the pcm.

Just call me Sean

iTrader: (1)

Stop checking alternators that way. It kills them, and the computer.

5Rangers

Earlier in this thread when I read what he was doing, I was going to say "wait for it, wait for it"... so predictable...

VFL

I would check the grounds as well.

memoniz

OK Dad, I'll take it under advisement.

Switched alternator, everything is right in Fordlandia. Will start checking the grounds for root of problem.

mrgooden

You do know an instant shock to an alternator like that can easily kill it right away right? A voltmeter of some type crossing the negative and positive battery terminal is a much safer and more desirable method.

Richard

5Rangers

And easier too, which I guess is the same thing as desirable..