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1970 MF135 fuel gauge power issue

Yesterday's Tractor Forums
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kaymcc

Member
Hello everyone. I have a 1970 MF135 gas tractor. I want to get the fuel gauge working but over the years the generator was replaced with an alternator with a built in regulator. The electrical diagram I have shows that the power for the gauge comes from terminal 4 of the regulator. Can I just tap into the 12V feed to the ignition switch or the ammeter? Seems a little dangerous to me to have 12V going to a gas tank. TIA
 
kaymcc said:
Hello everyone. I have a 1970 MF135 gas tractor. I want to get the fuel gauge working but over the years the generator was replaced with an alternator with a built in regulator. The electrical diagram I have shows that the power for the gauge comes from terminal 4 of the regulator. Can I just tap into the 12V feed to the ignition switch or the ammeter? Seems a little dangerous to me to have 12V going to a gas tank. TIA
Click to expand...
12 volts to the sender is fine as the sender provides a variable ground that makes the gauge work. You want to tie into the ignition circuit on a gas engine tractor, so the gauge is turned off when the key is off the feed to the ignition switch and the ammeter are live all the time. Tying into one of those places will run the battery down when the tractor is turned off.
 
Jim.ME said:
12 volts to the sender is fine as the sender provides a variable ground that makes the gauge work. You want to tie into the ignition circuit on a gas engine tractor, so the gauge is turned off when the key is off the feed to the ignition switch and the ammeter are live all the time. Tying into one of those places will run the battery down when the tractor is turned off.
Click to expand...
Gotcha. The previous owner cut the wires off the gauge and the sender at the tank. I think I know how to check the sender but how would you check the gauge? Which wire goes where on the gauge? Maybe all the hardware is OK. Just need to hook it up.
 
One post of the guage gets power (I would try power on the post at the Empty side of the gauge and the wire to the sender on the full side.

To test the gauge, apply power to the gauge and ground the sender wire. The needle should move full scale.
 
Jim.ME said:
One post of the guage gets power (I would try power on the post at the Empty side of the gauge and the wire to the sender on the full side.

To test the gauge, apply power to the gauge and ground the sender wire. The needle should move full scale.
Click to expand...
OK. Will do. Thx.
 
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