Fuel Gauge

[Ttumachy]

Going through the dash to try and get gauges working. Fuel gauge is sitting at E although I know it’s full. Both terminals on the back of the gauge show 6.04 volts so I know it’s getting power. 

 

To show full, do they need to be opposing voltage (so 6 volts and 0 volts from the sensing unit)? Or should there gauge show full with both terminals reading 6 volts? 

 

 

‘51 Plymouth. It has an aftermarket wiring harness installed by previous owner. 12v conversion, but step down to 6 volts for fuel gauge. 

 

 

Thanks in advance for anyone that can help!

[Sniper]

I have a 51 Plymouth.

 

There are two connections, one for power, the other to the sender.  There is no opposing voltage.  One will vary as the sender changes resistance, the other will not.

 

Go see what the voltage is on the sending unit terminal in the trunk. 

[Ttumachy]

9 minutes ago, Sniper said:

I have a 51 Plymouth.

 

There are two connections, one for power, the other to the sender.  There is no opposing voltage.  One will vary as the sender changes resistance, the other will not.

 

Go see what the voltage is on the sending unit terminal in the trunk. 

 

Thanks, opposing was wrong word.

varying, or different voltage was what I was thinking.

 

Top of the terminal in the truck is also reading 6 volts so that would say the wire is connected and there’s no resistance? Next step would be open the tank and check the sending unit then?

[Sniper]

38 minutes ago, Ttumachy said:

Top of the terminal in the truck

 

If you meant top of the tank, then is sounds like the sender is bad.

 

You can test the sender outside the tank by putting one lead of you meter on the terminal, the other lead on the mounting plate and putting the meter on ohms.  The reading should vary smoothly as you move the float from stop to stop.

 

Just be careful pulling the sender, you don;t want a spark there.  Use a brass drift to unlock the ring.

[Ttumachy]

On 3/19/2022 at 11:16 AM, Sniper said:

 

If you meant top of the tank, then is sounds like the sender is bad.

 

You can test the sender outside the tank by putting one lead of you meter on the terminal, the other lead on the mounting plate and putting the meter on ohms.  The reading should vary smoothly as you move the float from stop to stop.

 

Just be careful pulling the sender, you don;t want a spark there.  Use a brass drift to unlock the ring.

 

Just want to follow up and say thanks! The sending unit was completely corroded. It wouldn’t float with the fuel, and even if I moved it the entire thing wasn’t reading it. Fairly cheap fix, glad to have the fuel gage working again!