I have a '85 F250 with a 460.

We thought it had a bad ammeter because it just randomly jumped here and there. Keep in mind, truck worked fine at this point.

Took the alternator off, and we found a bad connection (FLD I think) after fixing that, the gauge was fixed.

Problem is, the gauge stays dead even during driving, and goes towards D if I turn anything on.

The alternator worked fine before, and it passed a alternator bench test after the problem started.

 

Forgive me, but what specifically is the problem?

 

Sorry

Ok, the problem is, that the gauge is accurate. I can use the truck as much as I want, without accessorys or lights. Seems to run forever this way. Once I start using any extra power, I run the battery dead.

 

I had the same problem once and mine turned out that the altenator was bad but not all the way it would charge just not enough. It didnt take hardly anything to run the battery down. iI would consider getting that altenator retested somewhere else.

 

I'd start with the basics and move up from there(forgive me if you've already done these but they're usually worth at least a mention)

In order, my suggestions are:

-check make sure the battery is full of water (good to do anyway)
-check the battery cables, make sure they're getting a good connection (good to do anyway, easy)
-check the grounding strap (good to do anyway)
-check/replace the voltage regulator--- (this is my bet as to where the problem is.)
-take the battery in and have it tested. (could be an internal short which makes it not take a charge-- if it's died a lot lately you might have fixed the initial problem but killed the battery in the process. Batteries don't like to die and come back.)
-if that doesn't do it, I'd then recheck the alternator. If you had it checked off the vehicle last time, have it checked on this time. Or vice versa.

 

"-check make sure the battery is full of water (good to do anyway)"

Brand new battery, and we've tried other batteries while this one was on the charger. Better safe than sorry.

"-check the battery cables, make sure they're getting a good connection (good to do anyway, easy)"

Done. One of our first steps, and we replaced the cables.

"-check the grounding strap (good to do anyway)"

I'm assuming you mean between the block and motor. I feel like a idiot now. I KNOW I have some ****ty grounding.

"-check/replace the voltage regulator--- (this is my bet as to where the problem is.)"

I was under the impression I had a inernal VR on the alt. How do I go about cheking the VR?


"-take the battery in and have it tested. (could be an internal short which makes it not take a charge-- if it's died a lot lately you might have fixed the initial problem but killed the battery in the process. Batteries don't like to die and come back.)"

Have had this done (even after buying a new bat)

"-if that doesn't do it, I'd then recheck the alternator. If you had it checked off the vehicle last time, have it checked on this time. Or vice versa."

I had it bench tested, but it's been tested while in the truck before I had the problem. I'll take it to be retested in the truck tomorow. I also have a brand new alt I could try.