I'm looking at buying a 1994 f150 straight 6. I noticed yesterday when I was driving it that the battery gauge would move when I gave it gas. I put a load on the battery by turning on the lights and running the a/c at high and the needle would still stay in the normal range. Right around the N and when I gave it gas regardless if a/c lights or anything was on it would move up to the R. Is this normal? The truck starts just fine and everyhting works on it. Also a new alternator was put in it 6 months ago. Thanks for any replys

 

If the idle is a little slow, or the belt is worn or loose, it could cause that. The guage will jump a little bit normally. If you think it's too much, there could be a diode open in the alternator too.

 

What do you mean by an open diode in the alternator? IF I hook up a multimeter and check the voltsand it goes up when I give it gas then is the alternator bad? Another question I have if I have the mutimeter hooked up and checking volts and I gove it gas and it doesn't go up does that mean it's a bad gauge? Thanks

 

The voltage will naturally go up, especially if you are idling with some load on the electrical system(defrost, wipers, lights, etc.) The more load you have on the system, the more the voltage will fluctuate from idle. Once you get the rpms up though, the voltage should hold fairly steady.

The alternator is actually an AC, 3 phase generator. To change it to single phase DC current, there is a pack of six diodes inside the alternator. One can go bad, and the alternator will still work, but not as well. This is a little bit hard to tell sometimes, unless you have a very good tester. You may want to take it by an auto store and see what they say about the charging system with their tester.

 

Thanks for the great info. The guy is having a new alternator put on it today. He has a 1 year warranty on it.

 

The guy had the alternator checked out with a digonostic check out and they tested it twice and it checked good. They didn't tell him why they thought the gauge was moving. So what do you guys think now? Thanks for any replys. I still think i'm going to buy it. But I wanted to se what you guys had to say.

 

Sounds like the owner is making a good faith effort over your concerns. If the truck is in good shape otherwise, I would go ahead and buy it. Start driving it, and see if it has any little bugs. The charging system I would consider small potatoes. I would be more concerned with rust and the condition of the motor and tranny.

 

The truck is in really good condition. It's a 94 ext cab f150xl straight 6 with 118,000 miles. It's a one owner truck with all routine maint. had been done. Original eng and trans. He is selling it for $2000. Over all it looks really good. Air blows cold the only concern that I had was the volt gauge moving when you give it gas. So what do you think. Thanks for all your help

 

Buy it, and don't worry about the guage.

 

I've got a 2 96 F150s one with a 302 and one with an I6. Both do the exact same thing and I've never had a bit of trouble. I say buy it and drive the crap out of it.