Hi I have a 1990 F-150 with a 302 in it. It has it's second brand new alternator, new battery, all new wiring for the harness and still won't charge. Any ideas? I'm completely stumped as to what it could be. Any testing methods or ways or finding a drain? Also pulled all the fuzes and it was still draining so theres no phantom drain from anything that runs off a fuze. Any help with this would be greatly appreciated!

 

I'm by no means an expert in anything regarding electricity. But since you ruled out everything connected to the fuses, you should start looking at anything with hot wires coming from the starter solenoid. That and the grounds... Sorry if i'm not of help, but welcome to FTE anyway!.

P.S.: You can check the wiring diagrams here -> BBB Industries - TSB's & Wiring Diagrams (link originally posted by ncranchero). I hope that helps.

 

I'm not an expert!

Even though your parts are brand new can you test them? Can you see how much your Alternator is charging for? Just pull the Negative Battery Cable off the truck. If the truck dies your Alternator is not charging the battery.

Check to see if your battery has Acid in it. Even thought parts are new sometimes you can get defected parts.

Okay, lets say you ruled out any problems the new parts, make sure you have a good positive and negative connection.

 

So checked the new alt. and the tester said diodes are bad! Replacing it again (from diff. manufacturer this time). Did the neg. battery terminal pull just to test it and the truck died. Thanks for the responses and I'll let you know how it goes! I'm running out of ideas on this one.

 

Alternator is bad. Make sure your connections are good. It should stay running with a good alternator with the cable disconnected.

 

Don't disconnect the battery while it's running , it can overload the alternator ( the battery is what determines the voltage output from the voltage regulator on the alternator )

 

it's a quick way of testing it with out having a meter and I never had that issue, may be on a Chevy but not a Ford.

 

So new alt doesn't fix the issue... I'm gonna end up pulling my hair out trying to figure this one out. Also should mention that I unhooked the alt overnight with zero drain on the battery.

 

The diodes became bad from pulling the battery cable off. The engine will not run very long with the neg cable off because it also need the exciter current from the battery in able to charge.

Taking the battery cable off can do a lot of damage to other item installed in the truck as the voltage can go as high as 100 Volts.

 

Echo ?????????

 

Okay so I've been checked wires and one question I had was the main ground does it go to the frame or block? I can't follow it as I have it up on jack stands but it goes above a fram peice underneath the block and disappears. Was wondering if I can attach a new one to the frame to replace that ground wire? Also it's a new alt since the battery pull. Haven't done that to this alternator and the truck starts and runs beautifully it's just not charging.

 

I believe your truck has the voltage regulator seperate from the alternator, i'd check that next. If the contacts inside are stuck closed it will drain your battery.

 

The ground cable from the battery goes to the engine block.
If you just hook it the frame I dough it will crank and you will have all kinds of problem as the main drive train is insulated from the frame with rubber mounts. You would also smoke the small ground from the engine to the body if you only grounded the frame.
You may need to ground the frame also if you pull a trailer but you will not need as big a cable to do it.

This photo shows the ground point with a red cable hooked to it.
They should have used a black cable.



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Thanks Subford! that helps! So do I need to remove the p.s. pump to access it to connect a new one and replace it? And akf250hd it has an internal in the gas and external in the diesels that much I know from the scematic I have on the alt.

 

Not according to what I found when I did a search on your truck but if you say it's internal then maybe your right. The parts I found said it was on the fender. Instead of replacing that ground wire, why don't you just ohm it out with a meter?

What model do you have exactly, year, trim, etc, etc?