1940 ih charging issue

bumblebee · Apr 5, 2017

I have a 1940 A Farmall that has an original type charging system, there is no voltage regulator, I think its called a cutout. It charges at 6.4 volts while running, shouldn't that be a little higher, like 7.5? Also, another thing that has me puzzled, on the original amp meter it shows that its not putting out any amps but when I hold the gizmo hand held amp meter over the cable, it shows over ten amps. When I turn the light switch to the high charge position, the tractor meter shows 10 amps, hand held shows about 15 amps.

My batteries last about 2 years and I don't use the tractor that much.

gene bender · Apr 5, 2017

You need to use an analog meter when reading volts. Your ammeter must be bad if you show tht many amps when charging. You can adjust the third brush for more amps but it sounds like its working just fine except for the meter.

John T · Apr 5, 2017

A 6 volt battery fully charged at rest is around 6.3 volts, so under a good charging system it should raise to at least 6.5 volts to around 7 subject to RPM and battery condition. You get max charge if you temporarily dead ground the gennys FLD post, try that and see what she does at high RPM. If she charges good with the FLD post grounded but NOT otherwise the LHDB light switch may be bad or not well grounded due to rust or bad connections. Charging amps depends on RPM and battery state and if shes in HIGH or LOW charge but Id expect maybe 1 to 10 or 20 amps subject to what genny you have, RPM and genny and battery condition. For more detail consult my charging troubleshooting procedure linked below.

JOhn T
John Ts Troublershooting

1940 ih charging issue

bumblebee

Well-known Member

gene bender

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John T

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