I have a 93 F150 w a 302. This has happened to me twice, both times after going through some puddles when it was raining:


The CHARGE light will come on, the Voltage gauge will jump and bury all the way to 18v,the radio will shut off, and the dash lights and headlights will suddenly get very bright.


The first time this happened, everything went back to normal after about a minute of driving.

The second time, it didn't. I drove the 4 miles home, and shut it off. Restarted and the battery light and gauge were still acting up. Let it cool down overnight, came out in the morning and the battery (which is newer) was stone dead. I jumped it, and it seems to start and run and charge just fine now.

I checked and it didn't appear any belts where slipping and there was nothing obviously wrong under the hood (arcing wires, etc).

Any idea what I need to do to keep this from coming back?


Thanks,
Jerry

 

Check your grounds. It sounds like you're loosing the battery grounds and the system is then running purely off the altenator.

 

Popa Tim,s right...sounds like "hunting" for a ground or positive to me as well.

Phillip

 

OK, thanks for that.

Looks like the battery is shot, must've overcharged or something and blown it. I bought a new battery and a new battery ground cable, I'll replace them both in the morning.

Thanks,
Jerry

 

Hey everybody,

OK, this morning I replaced the battery and the battery ground cable. The old battery waas leaking pretty bad, so I assume it probably blew from overcharging.

I made sure the connections on the ground cable were good and tight. I started the truck up, and the voltage gauge is still buried at 18V and the charge light is still on.

What should I try next?

Thanks
Jerry

 

Sounds like your "A" wire is not making a good connection at one end or the other. This is a yellow wire with a white stripe on it and is a small wire that runs from the generator to the fuse link. The fuse link also has a large black wire with an orange stripe on it at that point and the fuse link bolts to the starter solenoid.

 

OK, I found the wire you're talking about. I took it off at the solenoid, inspected it, and cleaned it with contact cleaner. I then disconnected the connector it's on from the alternator side and cleaned all those contacts as well. It's still doing the same thing.

Is there a way to measure to voltage on it to see if it's a wire problem or something, or is it possible to bypass it and try a different wire (I couldn't figure out how to do this with the specialized ford connector on the end)

Thanks,
Jerry

 

You can unplug it at the alternator and it should have battery voltage on it. You can also check the resistance from the plug to the positive post of the battery and it should be less than an ohm.

If this wire is good then you have a bad alternator and you need to have it replaced.

 

You could also have a bad plug that plugs into the alternator.

 

OK, I get 12V from the plug on the alternator. From the plug on the alternator to the battery terminal, I get 0.00Oms of resistance.

Does this mean my alternator's cooked? Is there anything else I can try?

Thanks,
Jerry

 

That wire controls the output of the alternator, did you check that plug real good and make sure it is making good contact with terminals it plugs into.

If you have a good connection at that point and the alternator has a good ground (battery neg. cable to block) I would say the alternator is bad.

But I bet it is that plug.