Please help with charging issue with my f150!!
 

So this is driving me bananas!!

98 f150 4.6

It stopped charging and left me stranded, I jumped it and was able to get home

I replaced alternator and battery...after this what would happen is my battery light would come on after I started and then go off and start charging after a couple miles of driving
I have been dealing with this for a couple months cause I don't drive it everyday

Well now what's happening is that it WILL NOT start charging on its own at all....I have checked every connection I can think of and cleaned all the connections I also replaced the 175a mega fuse

The only old part left is the Starter...could this cause this?

Here is the weird part if I jump it will another vehicle it starts charging immediately and will stay charging the entire day even with turning it on and off, but when it sits over night the next morning it will not charge until I jump again


Please help if anyone has suggestions for me!!!

I posted on the f150 forums but there is very little traffic there and no one either posts their fixes to the problems

I've seen a bad diode in the Alt cause similar problems....

You should try sending fastfredracing a PM. He either has one or worked on them at his shop.

Thanks Wayne I was hoping Fred would see this

Bob, I had the new alternator tested and all was good

it is quite possible your 'new' alternator is defective.

Not the starter.....most likely an autoparts store rebuilt alternator that was never good. If you still have the original alternator, take it to an automotive electrical specialist and have it rebuilt with good parts and pieces.

Try an alternator from the dealer. I've had a lot of problems with aftermarket Motorcraft alternators and starters.

Alternators that never turn the battery light off, or undercharge/overcharge after a few days. The starters sometimes have a solenoid problem that draws too much current to fully close the high amp contacts to the starter motor, or come with the signal wire that you can't remove to re-clock out of the way of the battery cable.

It takes a few minutes to test with a DVOM:
Key off engine off=_________Volts
Key on engine off=_________V
Key on engine on:
-at idle=_________V
-at 2500+rpm when the alt starts charging=_______V

Pull a battery cable.
Use the amp side of the tester to see if there is parasitic draw (other than radio/alarm/remote door locks).

It's probably a bad alternator.

Conclusion I hope!!

I took my "brand new" alternator back to the store and it tested good again but I demanded they give me a new one

I just installed the new one and it started charging immediately!

Thanks for the input guys!

Happy ending...I like those.

Just an FYI in case it did not fix it.

In this car the regulator has logic that controls the dash light and the initial field current comes through a separate fuse.

The new alternator may have enough residual magnetism to start without field current through that fuse. :(

I went through this mess 30 years ago on a 914- always tested fine at the store, manger was a jerk and wouldn't just replace it anyways. Finally went there when a new guy was working and watched him hook up the connections wrong on the tester, which of course showed a failed unit. Set me up with another one and problem solved.

I think that the slower speed of the test unit won't reveal some faults.

I will never buy a rebuild alternator unless I have no other options.

Glad you got yours fixed.

Sorry I did not reply sooner, I have been fighting with our shower all day, cant find the parts any where .
Glad you got it resolved, I just went through the same damn thing with my 930. I got 2 defective bosch reman alternators in a row. After the second, I spent hours trouble shooting , and still determined that all was good with my wiring, and my install. 3rd one was the charm, light went out, and charging at 13.7. Man , that is frustrating .
At least yours is an easy install .