Generator Field Coil

[Johnnykick]

Working on a 6 volt generator on a positive grounded 1955 Farmall. The generator passes the motor test (running a lead from the
battery to A), but fails the field test (no loss in rpm when connected directly the battery ground.)
Using this video at the link as a guide, I removed it and get 5.9-6.1 ohms. This generator was rebuilt about 3 years ago and was
perfect. Tractor set up for a year or so, now failed. Visual inspection shows nothing. Coils are nicely wrapped in fresh
wrapping. Thoughts?
Field Coil Test

 

[Janicholson]

Your test reading is out of specification. It may be that the wires are actually broken inside and barely touching. A 10 amp setting on a vom should let you check the amp draw by sending 6v through the coils from the brush end to the terminal end. As noted the amps should be 1.5 to 2.5 amps. no amps, or less than 1 amp is no good. Jim

 

[John T]

One problem may be at low resistances the accuracy of some ohm meters isn't all that accurate. If it fails the Field test, problems such as winding to winding shorts,,,,, or winding to case shorts,,,,,,,or intermittent connections,,,,,or changes in resistance when warm versus setting,,,,,,, may be at fault. Hard to say from here. Ive seen problems in the connection where the two fileds splice in the middle also.

John T

 

[Brownie450]

Possible residual magnetism gone after a year??
6 Ohms could possibly be bad connection with
multi-meter leads.
Jim

 

[Johnnykick]

Removed the field coils.See video for details.https://youtu.be/klMxfEwUzYI

 

[gene bender]

OLD TEST WAS WIRE A 60 WATT BULB IN SERIES WITH THE COIL TO TEST

 

[Johnnykick]

Well, mystery solved. I found a gentleman about 20 minutes from here who works on old starters/generators so I took it to him. He immediately identified the coils as 12v coils not 6v. So I told him it used to work, and now only occasionally (which was confounding my troubleshooting efforts.) (See my previous post and video on the history of this gen case.) He said that 12v coils will work "sometimes." So, he put 6v coils in and the generator is working fine. What a journey this has been. He also had a USA made 6v positive ground VR $110. I took a pass as the aftermarket is working for now.