8N ammeter shows constant discharge

jstreet · Apr 28, 2003

My 1948 Ford 8N's ammeter has shown a constant slight discharge for several months. Yesterday the battery finally died completely and I replaced it (old one was bad -- 12 years old with plates visibly corroded).
With the new battery, the engine started right up fine, but the ammeter still shows a slight discharge, even when I rev up the engine.
What is the next series of logical things to check? The voltage regulator looks ancient -- maybe orginal equipment. Can I just buy a replacement and install, or do these things need to be "set" somehow?
Maybe I also should take apart the generator and check brushes etc.?
I saw the recent post on a 4400 with discharge problems and some advice on re-polarizing the generator. Not sure how I do that (8N has a positive ground).
Any advice appreciated.

Anonymous Poster · Apr 28, 2003

First thing is to make sure you have the battery installed correctly.
Positive ground means the positive battery cable goes to the chassis of the tractor. If this is correct then it is probably the regulator or generator or both. The generator may need re-polarizing, not sure how to do that on a ford though.

It sounds like that your tractor is not charging the battery at all, is this right ?

jstreet · Apr 28, 2003

I may have solved my own problem. In case anyone's interested, after installing a new battery and having the ammeter still showing a discharge, I removed the generator rear cover and cleaned everything I could reach inside with an electrical-parts-cleaning spray. The brushes were filthy and had so much gunk on them that I think one was hanging up and not contacting the commutator very well. Put it all back together and lo and behold the ammeter reads well on the charging side.