I have a 1971 Supreme that recently the gas gauge constantly reads empty. Replaced sending unit about 2 years ago during restoration.

1. Unplugged the brown wire in trunk and gauge goes past full.

2. Grounded the brown wire and gauge shows 3/4 tank.

3. Switch on headlights and gauge drops below empty.

4. With brown wire plugged in and switch on it reads 16 ohms for a second then meter drops back to 0 ohms.

5. Checked and cleaned grounds, brown wire still reads 16 ohms then drops.

6. Drained tank of fuel & got about 7 gallons out of it, checked sending unit terminals and brown wire now shows 11.2 ohms constant

7. To cover all bases I checked voltage of brown wire at gauge and in trunk and it reads 2v. Don't know if that matters or not.

I am confused and way past my expertise in electrical with this situation. Do I have a bad gauge , sending unit or other electrical issue? Thanks

 

When you turn on the headlights and the gauge drops, does adjusting the dash light rheostat change the reading?

Read these:
https://classicoldsmobile.com/forums...e-problem.html

https://classicoldsmobile.com/forums...ild-check.html

https://classicoldsmobile.com/forums...e-out-car.html