Hello all, new to your forums here and am very impressed!

I just bought a 1999 F-250 Super Duty 4x4, which might be for sale again real soon if this keeps happening.

When I bought the truck the charging system was fine, I test drove the truck on a damp day, and didnt notice any problems. Drove the truck for a day, (dry) no problems. s

Next day, raining, charging system is fluctuating, and frequently overcharges real high, headlights bright and dim. I changed the alternator with a rebuilt (on a dry day,) headlights pulsing still, but no overcharge symptoms. New negative battery clamp, cleaned negative wire from battery term to engine block near starter, sanded and coated with dielectric grease. Seemed to slow down the flickering to a bearable point.
Drove to work the following day, (dry day) no problems.

Left work, solved some problems down the Elks for a bit, it is now raining, get into the truck, and immediately, the charging is going crazy again!, overcharging to the max, rev the truck up, charging needle snaps back to normal, then back and forth like crazy, drove it home all the time that this is happening, superovercharging. Once home, I rev the truck, its overcharging so high that the circuit breaker controling the inside dome activates for a second, shutting the lights out, then they come back on.

Today, no major rain, however it is damp, I started the truck, and its normal again.

Im thinking of running the hose over the truck to see if I can duplicate this symptom again.

Do you guys recommend pulling this alternator and having it tested? I just dont understand the wet/dry thing, but I would say its a definate factor.

Thanks in advance, and have a good Holiday!!!!!!

 

There is a common problem with the windshield leaking onto the fuse box and the GEM module under the dash, but usually you will have other weird problems as well.

I believe I would swap the battery out if you happen to have another one that would fit temporarily.

 

Hi Franklin, I drove the truck again tonight, (no big downpours), it was fine cruising towards the highway, but once I got on the highway, and started to speed up, it pegged on overcharge again, till I backed off and started to slow down.,

Now Im beginning to think that moisture doesnt have anything to do with it, if I keep the speed down, its fine, meaning city driving, however, if I rev it, even while standing still, or get on the highway, it pegs the charge.

I think Im just gonna yank the alternator out, and take it back to the shop I bought it from and have them test it, I cant see any other way that this is not the problem...

 

Your problem is intermittent, so expect them to put it on their machine, it will check ok, and then shrug their shoulders. It may have to get warm and be tested for a period of time before it shows up. Intermittent problems are always hard to find.

 

Yeah, went out this afternoon, truck was dead. Jumped with the battery pack, truck starts, voltage shows ok. Take out battery, replace with brand new battery, start truck, overcharges. Took alternator out, emailed company, ready to sell truck,, any takers???

 

Don't talk to me about car electricity, I think Im ready for the insane asylum!!

 

I started a new thread for the other poster. Here's the link to it. https://www.ford-trucks.com/forums/8...1970-f100.html

To start a new thread, look at the upper left corner when you are on the forum front page.