Hi all, quick question...

A couple of days ago my battery died, and I installed a new one. I cranked on the dying battery a little too long I guess, and after getting jumped the "amp" light was on. I figured the new battery would solve the amp light issue, but it didn't.

Weird thing is, the voltmeter is fine. I checked the new battery with my DVOM, 12.7 or so volts not running, 13.8 running, 13.2 with all accessories on.

The amp light is on dimly, and sometimes will go off.

Any ideas what the problem could be? I'm thinking cranking the starter for that long with a dying battery (high amp draw) could have fried a wire or something, but the confusing part is the truck is running and starting fine....

 

just tossin out ideas,

alternator,
voltage regulator,
blown fuse,
matching amp battery?

 

could be a ground. I had a shop pull my plenum and when they put it back on, they used the wrong size nut on a stud that was holding a ground wire on, I would hit a bump and the wire would not get good contact, and my amp light would come on, then later it would go off.

 

Thanks for the ideas guys!

I'm going to check the charging system today, the local AutoDrone has one of those fancy testers.

That plenum ground strap may be something to look at. I had the plenum off not long ago to do the EGR tube. The plenum strap looked like it had been wrapped with electrical tape at some point by a previous owner.

 

Nope, most all look like that.

 

I know what you mean, the black coating on the strap. This one had actual electrical tape on it though, and was pretty twisted up.

So, I replaced the ground strap from upper intake to firewall, and it didn't make a difference at all.

I also did some more checking with the DVOM. On the alternator harness with the three wires coming out of it, the green/red is the wire that feeds the amp light. Back probing that, with the truck running, I got a reading of 3v. That doesn't seem right at all. fordfuelinjection.com shows this circuit as having a 20a fuse, but I can't find it listed in the owner's manual. The manual does list a 50a mega fuse in the underhood box, which is fine.

So, this is all leading me to think the voltage regulator is bad?

Don't want to seem cheap, but I'm not a fan of throwing parts at something no knowing if it will fix the problem or not.

 

Update: I figured out the problem with the help of a friend. It's the single wire connector on the alternator. Wiggling that will make the light go on and off, so I took it off and cleaned the terminals, and all is well.