Fuel Gauge Pegged to Full

[trapper]

Ok as i am working on my truck, i swapped out the rear tank for the Big plastic tank and skid plate on the old C&C F-350 , the diesel tank is a 2 wire plug and my old tank was 4 wire plug, when i hooked it up my fuel gauge peggs out to full and only will move if i ground out the Yellow wire........... the 2 wire plug on the tank has a yellow wire and a black wire, but when i hook them up the fuel hand stays pegged to full, i remember it actually worked once lol then when my alt went it stopped working , i tried reversing the wires but no luck, what else can i do to get this thing working ?

i know im a noob


plus the black wire on the pigtale for the tank is for ground right ?


ps i read somewhere that someone else had a similar problem and his gauge worked and came off of full if the float inside got a good contact

 

[Diesel_brad]

What year did you get the cab n chassis tank out of

 

[trapper]

it was in a 88 model

 

[subway]

the resistance readings have changed over the years, not sure the cut off but they are reverse of each other and differant resistance levels.

 

[trapper]

well im usein the diesel gauge cluster and the diesel wiring harness under the hood

 

[trapper]

Hey towcat you got a diagram ?

 

[plywood]

I have the same problem on mine after the conversion.

On our years it must be that when there is 0 volts the gauge says full.

 

[trapper]

Well i put a volt meter to the yellow wire and it came up like 8.23VDC and the red wire comes up 8.32VDC if im not mistaken, with the yellow or red hooked up to the yellow wire on the pigtale the black wire comes to like 0.32 VDC the other brown wire has nothing going to it, sill aint figured it out

 

[flareside_thun]

The sending units operate on ohms and that's the way they're supposed to be measured in reference to testing and TSBs.