Problem with fuel gauge

[Q78buick]

I have a 1978 Buick Regal. My fuel gauge isn't working. I have replaced the fuel sending unit as well as the fuel gauge but it still reads past full. Can anybody help me

 

[jacobdavis1979]

Do the sending unit and fuel gauge match? Fuel gauges are just a resistance meter. If u have a fuel gauge that works on a 0-90 ohm load but a universal sending unit or vice versa it will read past full.

if its all factory check your connections i dont remember for sure but i think if u have a bad ground it will peg past full.

Now if you bought an after market gauge check if it has a built in voltage regulator. If not you will need a 5 volt voltage regulator to drop the voltage cuz if u are running a full 12 volts into that gauge it will peg past full.

 

[pontiacgp]

if your other guages are working properly it's probably the ground wire at the tank is broken or disconnected

 

[Fox80]

When I had this same problem on my car, I replaced the sending unit, redid the ground wire, and it still didn't work correctly. My problem ended up being the pin where the dash cluster plugs into the harness. Cleaning up all the pins also brightened the gauge light bulbs, so might not hurt to check that as well

 

[Q78buick]

I bought the sending unit brand new. I believe the ground is good as well as gauge itself. I was told their is a positive that runs from sending unit to firewall could that be the problem?

 

[Fox80]

That could be as well, mine was fine so I can't say what to look for

 

[Q78buick]

So therein a positive wire that runs from the front to top of sending unit. Does it happen to be red.

 

[jacobdavis1979]

i think mine was red

 

[Fox80]

Mine was red, it has the push on connector that hooks to the top of the sending unit

 

[Q78buick]

Ok thanks. Mines didn't have it on their but I found a wire that came from my firewall that was green I traced it and turns out the green wire was connected to the red wire someone must have cut. So putting the right wire on and a push for it I should be good right. Do they sell the push at auto stores?