Fuel guage - 6V or 12V?

[put-put]

I had the instruments rebuild on my 54 3100. now that i have finished the restoration, the fuel guage doesn't work. I asked that it be converted to 12V, because i changed everything else over to 12V. The guage reads empty at all times. i have put 5 gals into the tank, but still reads empty. I checked the voltage at the tank sending unit and it is 11.8V. i removed the wire and left it disconnected, switched the key on and the instrument read E; i then grounded the wire to the tank sending unit and it still reads E. Any suggestions? Is it possible it was wired for 6V and doesn't have enough current? If so, what's the easiest way to check it?

thanks, Put-put

 

[Kens 50 PU]

Hey Putput, you may have a classic case of the sending unit blues. If the float has a small hole in it, it may be "soaking up" gas causing it to sink to the bottom showing you a empty reading. Check to see if that's the case. If not, we'll start from scratch.

 

[vwnate1]

If this is the same post thay was on the yahoo list , the power is to the wrong post , it needs to go to the left most or lower post and then the gauge should read " full " when you disconnect the sender from the back of the gauge , the gauge needs good grounding to work too .

 

[Kens 50 PU]

Hey, putput, go to the electrical section of this site. There was a post there that might give you some more ideas.

 

[put-put]

Nate, the instrument is wired correctly, power to bottom left post. When i disconnected the wire from the tank sensor, there was no change in the guage reading. is there a resistance reading i can do across the fuel gauge?

 

[vwnate1]

O.K. , disconnect the sender wire at the gauge head and see what happens , it the gauge head has power and a good ground , it should read full . if not , the gauge head is junk and needs replacement .

If the gauge goes to full , then ground the sender post , this should drive it to or below , empty ~ if not , the gauge head is junk and need replacement .

Remember : when you have the gauge off the dashboard , it's NOT grounded and won't test correctly until you add a known good ground wire .

Always make primary tests at the gauge head as the sender wire may be shorted or open circut .

 

[put-put]

Got it!! Thanks Nate

Nate,
this morning i was looking in my Assembly Manual for info on how to take the instrument cluster out if needed. I noticed that for my 54 it showed the fuel gauge wiring connected the opposite of what you recommended. i then went out to the truck and double checked, it was wired as you thought it should be. I continued with the checks and when i disconnected the sensor wire and turned the ignition on, the gauge moved more to the empty side! this told me that the wiring was probably reversed on the 54. I had the instruments converted to 12V, so i reversed the hook up and it works!!!!!

thanks for your help; your input lead me to the solution.

 

[vwnate1]

Whoops ! I wasn't paying attention to the fact you'd said it was a '54 , the year the dash changed .

Glad to hear you sorted it out though .