Hey, I was looking into the wiring from my alternator and found it's all cobbed up. Does anyone have a wiring diagram for the alt on the 6.9 engine?? There are three wires comming off mine and there were about three more connected to the main one off the alt. Where are they going?? the voltage regulator is external. What are the wire on that for? Any info will help. Thanks.

 

Here's a little bit later model diesel, but I believe it's the same.

http://www.autozone.com/autozone/rep...20and%20Bronco

 

That diagram Franklin posted will only work if you have a truck with Warning lamps instead of Gauges.

The routing of the altenator wiring for a truck with gauges is different.

 

Well I took the alt to autozone and had it tested. It tested fine. Came home and threw it back in and drove down there. Not charging. I don't get it. I went over the wiring from the alt and it all looks good. What am I missing??? The power line off the alt should go back to the starter relay right?? Does the alt need a ground wire?? The way it was before it did and it went to the neg battery terminal. I have the field pole connected to the regulator. A y ideas here???

 

The Altenator Grounds through it's bracket normally.

Did you have the regulator tested? They can test those as well.

Do you have gauges or Idiot lamps?

 

Yeah they tested the regulator and it's fine. I gave gauges.

 

With the truck off, take a meter and test for voltage on the "bat" terminal of the alternator. You should have 12v with the truck off. If you don't, then the fusible link is blown in that wire.

If you have that, then check the "a" terminal of the regulator. It also should have 12v with the truck off.

One of the wires going to the regulator should be red/green or green/red. Put your meter on this wire and the other lead of the meter to ground. You should have voltage on this wire with the key in run and the engine running. This wire will be located on the "I" terminal or the "s" terminal, however your setup is wired.

 

"S" terminal for Gauges.
"I" Terminal for Indicator Lamps.

This diagram is one I made for 1973-1979 trucks, but it's simular to 1980-1986's.

 

Thanks for the info guys. I'll be doing some tests when I get home!!!

 

What gauge wire should the power wire off the alt to the relay be?

 

Soo I'm looking at this stuff. I have 12volts at the bat terminal on the alt. Nothing at the A terminal on the regulator because the wire goes nowhere. Nothing is connected there. What is supposed to be there??

 

Well I hooked the wire for the A terminal like in the diagram and it's now charging 14 volts at 2000 rpm. Good enough for me!!! My ammeter isn't working but I'll take what I can get right now.

 

The OP's profile says 1984 F250, and he states he has a 6.9.

1983/85 F250/350: There are 7 different alternator wiring harnesses, SEVEN!

It makes a difference if the truck has a 40 - 60 amp alternator with gauges or with idiot lights.

Ditto for the 70 amp alternator.

If I knew exactly what the OP has, I might be able to locate a new original harness, that's been obsolete since grandma was a girl.

 

pulling up an old thread off of a search. I have 83 f150 with guages and am having a problem with the charging system. When I start the engine, the amp meter pegs to full max for about five seconds and then starts to bounce systematically at an interval of about a second and a half. The lights dim in sync with the guage. I first replaced the regulator and then the alternator. I am getting a good ground to the engine block. On the diagram above, i see a capacitor coming off of the regulator. Any chance this could be bad and cause this? Any other suggestions? Thanks in advance for any help.

 

Check the ground for the regulator.