2007HarleyDavidson

I am working on a 1992 F150 with the 5.8L V8 with 121,000 miles on it, It had been sitting for about 4-5 years. It started right up with a new battery.I have it running pretty well other then the battery gauge fluctuates from one end of the word "Normal" to the other on the gauge. When you start it up no ac/radio/lights, it is at the high end, when you turn on all the electronics it will drop to the low end and if you start to rev the motor it will bring it back up some but when you let off the accelerator it drops back off again. It had a new battery and it started to leak acid so I had that exchanged and has another brand new battery, brand new belt and the tension arm is in the correct range and is in great shape. There was a new alternator put in the truck about a year before it was parked. When the truck was parked the gauge never moved. Any thoughts? new alternator maybe? I don't have an autozone near by so I cant just have it tested.

Ol' Navy

Mine did the same thing when the battery wasn't getting a charge from my alternator because of a dirty battery terminal. Check your battery terminals and grounds and clean them, and if the problem persists it's probably your alternator. You could always un hook the positive from your battery while it's running and if it goes dead your alternator is bad.

etex

Not a good idea to remove the battery terminal to test the alternator. This can damage the electrical system.

redneckfordf2502002

Probably altenator my 88 F150 did the same thing after sitting so long. Put an alternator on it fired her up and drove her no problems. Electrical parts when they sit go bad faster. (my 88 only has 56K on the entire truck and it had the original alternator in it. Our 89 F350 has 330K miles on it with original alternator and it still worked (I put it on my 88) the longest that truck sat before I got it was a couple hours (it was owned by a hauling company originally then it went to my buddy whom is a wood cutter).
Trav

Forge-World-FORD

If it s still a 2g alt those are pretty crappy anyway. Low amps and pretty much anything electrical pulls a lot of power from it. You can do a quick voltage test. With the engine running use a multi/volt meter on the battery like if you were checking battery voltage. While running it should read alt output.

Gobie

I have a 99 f150 with the 4.5. My battery gauge goes to high when I'm driving. Just had alternator checked and everything reads good. They said I probably have a faulty gauge. Dunno.

wde3477

Aside from resurrecting a thread that's been dead almost 9 years, suggest you may have better luck posting a new entry in the correct vintage sub-forum, this sub-forum is for the 87-96 Gen 8's and 9's.

All that said, had a problem here with the instrument panel flexible circuit connection to the battery gauge. Was reading irregular lows and highs, and just beating on the dash would cause the needle to jump around. Solution was to take apart and clean, then make sure the 'fingers' from the panel were shplayed out to make solid contact with this flexible circuit.film.

Good luck!

Steve83

Go to your forum settings and turn OFF the option to "Show related threads".