"Vince, Once again, I bow before the Master.
This is probably a no brainer, but... I am replacing an alternator, 165 amps, on a 1989 Ford ambulance, 7.3-liter non-turbo diesel, 1-ton van, which I did not remove. I have the Positive to Battery, the Negative to Ground, and a small green wire with a push-on connector, round type to go over a threaded post, which I am uncertain of its intended location, although I believe it must go to the terminal on the alternator which has a wire connected and feeds into the body of the alternator. The owner of the van called the alternator rebuild shop that it came from, and the technician there said to leave it off. We started the van, but no output to the battery from the alternator. After researching the web looking for any kind of wiring diagram or schematic, I do find several articles stating the alternator indicator lamp feed must go to the alternator to generate field winding excitation. Please advise.
Long time reader...
Several time questioner...
Claude"
Answer: Inside the 1989 Ford Ambulance Alternator
In order for an alternator to start charging, it needs a little "jumpstart". Providing the FIELD terminal of the alternator with B+ voltage does this. In a 1989 Ford E-350 the wiring is as follows:
- Circuit 38: black/orange wire coming from the B+ terminal of the alternator to Fuse Link F, 14 GA Green, starter relay and the left and right batteries.
- Circuit 35: orange/light blue wire going to the F terminal of the alternator from the F terminal of the external voltage regulator.
- Circuit 152: light blue/white wire that goes to the A terminal of the voltage regulator that is spliced off Circuit 38.
- Circuit 904: light green/red wire from the S terminal of the external voltage regulator to the electronic control.
- Circuit 48: white/black wire from the S terminal of the alternator that may or may not be there and is not used in this application. This went to the instrument panel ammeter in earlier models but is replaced by Circuit 655.
There are no green wires indicated in the Ford Factory wiring diagram in any of the charging system circuits.
That's all for this week. Feel free to browse the archives for past topics and other resources. And, as always, if you are stuck and need an immediate answer you can always call Vince on the phone. For a limited time new callers get the first three minutes free!
Vincent Ciulla - Vincent Ciulla has been a professional automotive technician for over 35 years and is a certified master technician with experience in ...
