Not sure what is going on, I checked the wiring harness, tried a new battery, changed the alternator out with a ford one. Lights flicker at idle. Producing high voltage like 15.4 at idle even with new alternator. Not sure what to do, its annoying and seems to be unreliable. Fusible links? Grounds? How do I eliminate the problems?

1999 F250 super duty 5.4

Thanks

 

So, after replacing the alternator it's doing the SAME exact thing, or did it change in any way?

Sounds like the battery might even be bad and not charging...

With a volt meter, go to the big post on the alternator, and see what voltage you get between that and the + side of the battery and report back.

Also, check the voltage between the alternator case (ground) and the (-) side of the battery, engine block, AND body AND frame. Report back.

 

Where did you get the alternator from? I have encountered instances where the new alternator is bad as well. Ran into this problem on a 4.6L Thunderbird, Land Rover Discovery, and an explorer. The scary part is the Land Rover alternator was a dealer part!!!

Also, my truck dims out at idle vs. on the gas, even with a brand new Motorcraft Alternator.

 

The alternator was from Autozone originally, then I switched to a Ford alternator just yesterday. Problem is still there. I thought it was the battery at first too. I bought a new one, put it in and no change. I checked the voltage and it varies from 14.4 to 14.6 at idle, and the lights pulse. The voltage is the same from battery + to alt case and from + post on alt to battery negative, and + on battery to body. Today I turned the heat to high and the alternator actually cuts out, you can hear a change in the sound of engine and the battery light comes on for a brief second. So I had about three autozone alternators that I tried and now this one from Ford, a new battery, checked wiring for cracks and exposures. Not sure where to go from here.

 

Just a thought. Check the battery cables, in particular the connectors on the ends. I had a very similar problem a few years ago and traced it to a poor connection between the battery ground cable's conductors and the molded-on lead battery terminal clamp. The flakey ground resistance drives the voltage regulator crazy.

 

Clean up your battery connections, but I'd also check the voltage on the battery while running in AC. It seems unlikely that you would get two alts with bad diodes, but it would explain the flickering if cleaning up the terminals doesn't help.

Try disconnecting the battery and checking continuity on the wires. While the DMM is connected, wiggle the terminals to determine if they are loose. There should be two wires on the voltage regulator that is connected to the pos battery terminal.

 

What I suggested was to check for voltage between the ground of the alternator and the (-) side of the battery, and the body and chassis grounds, because I want to see if there is ANY voltage difference meaning a bad ground.

Same for the (+) side of the alt to the (+) side of the battery.

Still stumped.

Did you reuse the regulator? Or did they come with the alternators?

 

The other thing is if I recall the voltage regulator and all that fun stuff is in the alternator. Follow up with Krewats advice, then if that dont work bust out your multi meter on the alternator itself. I would also check the contacts for where the harness goes into the alternator. Like I've said on other threads... dielectric grease and wd-40 are the duct tape of an electrical system!

 

I'm trying to remember here, but a ground potential would mean less voltage. IxR=E, so more resistance means less voltage. Pretty much Kershoff's voltage loss.

 

Ok I cleaned the terminals inspected all wires going to and from alternator, battery and starter. Only problem I found was at the solenoid and the end of the wire that attatches to stud had a crack in it and was a little corroded. I cut off the end and soldered on a new end. I did some google searching, and found another guy that said the fusible link caused this problem on his truck and he soldered the fusible link and it fixed it. It is weird it only happens at idle. So I am going to try that next I guess. Unless anyone has any other help then can offer.

Thank you

 

the alternator came with a new regulator, I did not reuse any old parts.

 

Maybe try a new wire from the battery to the alt. the big one. Sounds like the alt output is having a hard time getting to the battery or there's abad connection at the key on wire going to the alt. You could try a jumper from batt neg to alt frame also to eliminate possible bad ground connection. Reg charging voltage should be 14.5 volts at idle.


Dick

 

I put a jumper from the battery + to the alt + and the - battery to the alt case. No change. Lights still flash. Also, its 20º here today, and sounds like another coil has stopped working. Where do you get a good deal on a set of coils for these trucks? its got 240k on it, maybe time to retire?

 

Here's a pic from the EVTM for 2001 - notice the "A" terminal on the alternator is the "sense" input, and that there's a fusible link inline. If this line is not supplying sense voltage to the regulator, I believe it goes to full charge.

 

Just my non-mechanic two cents but it sounds to me like your revs are just low enough at idle to not put out quit enough volts. If it goes away off idle you may just have too much of a load at idle due to other electrics. Apples v. oranges I know but this isn't uncommon on bikes, older ones anyway.
O.K., feel free to jump all over this explanation.

Later...
Brewster...