I have a 1990 F-150 5.8 and the voltage guage keeps rising and dropping constantly when i'm stopped, otherwise it's fine while i'm driving. I checked the battery connections and that doesn't seem to be a problem. It idles quite roughly also and sounds like it's going to stall when when the voltage starts to go crazy at idle after about 20 seconds or so.

any help would be appreciated!

-Preston

How far does the voltage fall when idling?? It is normal for voltgage to move a little bit when you stop, but it shouldn't go down enough for the vehicle to feel like it is going to stall. That would indicate that your alternator output isn't enough at idle/the alternator is going bad. Have you had any other weird electrical problems (dash lights flashing, other gauges turning off, flickering lights, etc)

Sounds like your alternator is about to die...I agree

i just got my alternator checked as of yesterday and the alternator shows that it's putting out around 11-12 volts and at 13 when you rev the engine. I thought it was the alternator...just figured I would check w/ people that knew what they were talking about. So my next move i guess would be to go get a new one.

Thanks for the help!
-Preston

i just got my alternator checked as of yesterday and the alternator shows that it's putting out around 11-12 volts and at 13 when you rev the engine. I thought it was the alternator...just figured I would check w/ people that knew what they were talking about. So my next move i guess would be to go get a new one.

Thanks for the help!
-Preston



Don't get a new alternator....that is normal voltage output. That means the problem lies elsewhere.

Voltage Regulator.

Voltage regulator should be in the alt on that one.

Is the voltage regulator attatched to the alternator?
Sorry... i'm still learning about these things.

well...i put a new alternator on...found out that it was the "pcv" valve...

thanks for the help, i thought it was the alternator also...? but i guess not...

-Preston