The Ford Barn

Jeep09 · 07-24-2025, 03:18 PM

Is there any harm in using a 12 volt 90 amp alternator with this gauge

Model51 · 07-24-2025, 03:26 PM

The production Ford 1935 amp gauge works by sensing the magnetic field induced in the wire looped on the back side of the gauge and is not directly connected to the wiring loom. I don't think you can burn it out but I doubt it will read properly and the needle may just sit at the max reading all the time. Maybe someone with more knowledge on electrical circuits can provide a more definitive answer.

cas3 · 07-24-2025, 03:52 PM

The only time it would see high amps is if you put a dead battery in and jump started it.
Otherwise, in normal use is should zero out once the battery is at full charge

Jeep09 · 07-24-2025, 06:42 PM

thanks for the replies

koates · 07-24-2025, 08:03 PM

It is very doubtful that your 12 volt 90 amp alternator would ever charge at 90 amps in your car.. If your battery was way down and other items turned on such as headlights, heater fan, radiator fan, radio etc then it still would not reach 90 amps charge on the meter because all the loads are a discharge on the gauge ( thats if they are wired through the gauge). Even if the gauge needle pegged out at max charge it would not be damaged because the gauge is an induction type with no direct electrical connection. Regards, Kevin.

cas3 · 07-24-2025, 11:18 PM

Sponsored Links (Register now to hide all advertisements)

a better explanation from Koates, thanks!

07-24-2025, 03:18 PM	#1
Jeep09 Member Join Date: Oct 2023 Location: Canuckistan Posts: 40	1935 Ford amp gauge Is there any harm in using a 12 volt 90 amp alternator with this gauge

07-24-2025, 03:26 PM	#2
Model51 Senior Member Join Date: May 2010 Location: Fairfax Station, VA Posts: 777	Re: 1935 Ford amp gauge The production Ford 1935 amp gauge works by sensing the magnetic field induced in the wire looped on the back side of the gauge and is not directly connected to the wiring loom. I don't think you can burn it out but I doubt it will read properly and the needle may just sit at the max reading all the time. Maybe someone with more knowledge on electrical circuits can provide a more definitive answer. __________________ 1935 157" 1 1/2 ton stake truck undergoing full original restoration 1936 131 1/2" panel truck rescue preservation Author of the 1935-1936 Ford Model 51 V8 Truck book published by the Early Ford V8 Club of America

07-24-2025, 03:52 PM	#3
cas3 Senior Member Join Date: Jan 2011 Location: Beverly Kansas Posts: 5,298	Re: 1935 Ford amp gauge The only time it would see high amps is if you put a dead battery in and jump started it. Otherwise, in normal use is should zero out once the battery is at full charge

07-24-2025, 06:42 PM	#4
Jeep09 Member Join Date: Oct 2023 Location: Canuckistan Posts: 40	Re: 1935 Ford amp gauge thanks for the replies

07-24-2025, 08:03 PM	#5
koates Senior Member Join Date: May 2010 Location: Melbourne Australia. Posts: 2,185	Re: 1935 Ford amp gauge It is very doubtful that your 12 volt 90 amp alternator would ever charge at 90 amps in your car.. If your battery was way down and other items turned on such as headlights, heater fan, radiator fan, radio etc then it still would not reach 90 amps charge on the meter because all the loads are a discharge on the gauge ( thats if they are wired through the gauge). Even if the gauge needle pegged out at max charge it would not be damaged because the gauge is an induction type with no direct electrical connection. Regards, Kevin.

07-24-2025, 11:18 PM	#6
cas3 Senior Member Join Date: Jan 2011 Location: Beverly Kansas Posts: 5,298	Re: 1935 Ford amp gauge Sponsored Links (Register now to hide all advertisements) a better explanation from Koates, thanks!