mf 35 postive grounded gas gauge

[john in the highlands]

I'm getting around to fixing up the old gal. I've got a new postive grounded gas gauge, seems only to take 3 volts to make it read full (using 2 AA batteries. However the new sending unit and my old one, no matter what the gas level, in my 12 volt system sends way to much voltage. Since the TSC catelogue only offers only one postive grounded gauge, do I have the wrong mf 35 sending unit? Am I missing some voltage reducer? I've been playing with the sending unit, There's more voltage resistance the lower the gas level, so that part's working to indicate the gas level change.
 

[Tony in Mass.]

Look for the wiring diagrams in the FENA website, sounds like it needs a reduce don't it?
 

[35 MF]

Why did you get a positive ground gauge? I believe all the 35's were negative ground.
 

[john in the highlands]

mine's a positive ground. Apparently tractors and trucks earlier on were positive grounded to reduce the chance of shorting out causing an explosion. Also, copper wires originally weren't coated so they corroded quicker if the ground was negative.
 

[john in the highlands]

Thanks, Ill try that
 

[35 MF]

Some tractors that were 6 volt were positive ground like an 8N but I'm pretty sure a 12 volt MF 35 is negative ground. I know there are people on this forum that would know for sure.
 

[Chip812]

Mine is negative ground. 1961 MF35 Deluxe
 

[john in the highlands]

I finally found a postive grounded gas gauge from a&i, It says 12v on it. I used a circuit tester on it (2-AA batteries, 3 volts), my fuel sender is 30-250ohms, when the sender is at it's highest resistance using the 3 volts, the gauge reads empty and then reads full with 30ohms resistance. it reads full all the time in both with the 12 volt tractor battery. But, the gauge only works in both cases , when the ground is negative.
U.K.mf 35 tractors were 12 postive grounded, why is my U.S. tractor postive grounded when the rest are negative? It's a pain in the butt! I'm trying to get my supplier to replace the gauge, it's got to be deffective!