OK Guys, I have another issue that I'm stumped with. 1989 F250 with a 7.3 idi 4x4 5 speed
My battery light on the dash came on and the amp gauage was low on the output, so I checked the voltage output on the alternator and it was low (11.38 volts ) so I replaced it and no changes in the issue. I figured that the voltage regulator may be bad so I drove the 20+ miles to town and stopped into O'Reillys and had them check all the charging parts. After putting the tester on and putting it under load the charging system functioned properly and the battery light went out and the amp gauage showed a proper charge was accuring. 3/4 of the way home the battery light came back on and the gauage showed a low charge again. Thinking I may have a dirty battery terminal I cleaned all four of them and the issue still exists. Does anyone have any ideas on what I should look at next? Any help will be appreciated, thanks in advance.

 

I used to have the same charging problems on my 1990 until I upgraded to a 130 amp 3G alternator. Here is a wiring diagram.

 

This problem just started and I've had the truck for nearly a year with no issues in this area. It doesn't make sense to add amps when everything was fine prior to a couple days ago. Thanks for the input and it may be my solution although I'm hoping that their are others that may have a solution to my problem without having to go through this extensive change.

 

I understand what you are saying. I upgraded to the 3G because it helps eliminate connections problems with the external voltage regulator and charges better than the 1G system at low rpms driving around town. The cost was nearly the same for the 130 amp 3G alternator as the 90 amp 3G alternator and allows for improving my stereo system when I get around to it.

 

Changing an alternator and a couple wires is hardly an extensive change. It's a bolt on deal for only marginally more than a 1g or 2g. If you have a 2g, note they tend to melt the wiring and could be a fire hazard. For me at least it's not worth messing with a 1g/2g alternator, when they die or the regular dies I replace with 130 amp 3g. My time is worth enough to myself that I'd rather just upgrade and be done with it.

Aside from that, just the field to +12v and measure voltage, should go up to 16v-17v at full field. Only do this briefly as the alternator will get hot, but it verifies the alternator works.
Check that the regulator is getting full battery voltage at the key on 12v battery terminal (A)
Check that with key on you are getting near battery voltage at the key on 12v terminal (I)
Check voltage at the field terminal output on the regulator (F) and at the alternator field terminal when voltage is low. You should be getting full battery voltage at both. If you have that at the regulator output terminal but not at the alternator, replace the wire. If the other terminals on the regulator check out but you don't get full voltage at field while battery voltage is low, the regulator has failed.