IH/Farmall 140 charging system

I'm working on my brother in law's 1973 IH Farmall 140 remotely. It appears to have a 12V Delco generator with external voltage regulator. My question is this: From where does the generator's field coil
receive its ground? Does it ground through the voltage regulator contacts OR is it internally grounded with the voltage regulator supplying voltage TO the field coils? If it is the former, then it would be
critical for the voltage regulator to have a good contact with the tractor for a good ground-right? Thanks. Phippsburgh
 
It's an "A" system... one end of field windings connects to the ungrounded brush (for power), the other end grounds through the regulator.

The regulator needs to be grounded for this reason AND for accurate voltage sensing for the regulator component to work.
Official IH electrical manual

If link doesn't work, cut and paste into your browser:

http://www.cleancomputes.com/Cub/Blue%20Ribbon%20Service%20Manuals/GSS-1310%20Electrical/index.html
 
What Bob says - the field circuit is supplied internally from the armature grounded externally thru the regulator.

Also as Bob mentions it is ABSOLUTELY CRITICAL the regulator be solidly grounded regardless of the field circuit type!

Incidentally on each my generator-equipped tractors I have run a dedicated ground wire between the regulator bases and the grounded battery posts. It's not "original" - but it has eliminated a lot of charging system problems.
 
That is a good modification! I could see that fixing a lot of charging issues. How big of a wire do you use?

Al
 
Al - I use #14. The max current the ground wire might see is only a couple amps....will work fine with smaller (#16 or #18) wire also.
 

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