67 Gas Gauge

[Curt S.]

Further help needed on my 67 gas guage. In a previous thread, the gauge was reading behind the empty mark. I changed the gauge and reversed the wires on the gauge. It now reads full when the tank is almost empty all the time. I also changed the wires back and the gauge went back to behind empty. It is a new dash harness and new rear harness. Bad new sending unit? Any help/ideas will be greatly appreciated. Thanks Curt

[Stephen L.]

Re: 67 Gas Gauge

I would substitute a potentiometer of about 200 ohms in place of the sending unit (jumper wires) and then watch the gauge as you turn the potentiometer. If the gauge "follows" the movement of the pot then the wiring circuitry is good and you have a sender problem.

Connect the pot with one lead to one side and the other to the variable wiper.

Off hand I don't recall the actual resistance of the sender. Possibly someone could chime in..... That would be the approximate value of the pot used.

[Joe R.]

Re: 67 Gas Gauge

I would substitute a potentiometer of about 200 ohms in place of the sending unit (jumper wires) and then watch the gauge as you turn the potentiometer. If the gauge "follows" the movement of the pot then the wiring circuitry is good and you have a sender problem.

Connect the pot with one lead to one side and the other to the variable wiper.

Off hand I don't recall the actual resistance of the sender. Possibly someone could chime in..... That would be the approximate value of the pot used.

Steve,

It appears that 90 Ohms is the correct value, from this article:

http://www.lbfun.com/warehouse/tech_...rFuelGauge.pdf

Joe

[Stephen L.]

Re: 67 Gas Gauge

Then a 100 or 200 ohm pot would work just fine. What you are looking for is controlled movement along the scale on the indicator. Higher ohm pots will just give you less resolution to the pot movement with less control with the pot shaft.

[Ronald L.]

Re: 67 Gas Gauge

For starters...
Take all the wires of the sender, with the tank MT the resistance should be zero, when full 90, if it is anything else - you have one of those cheap china pieces of junk. I've not seen one that measures correctly. You can do this by getting a stick (non conductive and either lifting up the float or pushing it down to get these readings, easier if the tank is near empty.

If you get 0 ohms at MT and 90 in the full up position your issue is in the dash and or wiring ground and that diagnostic was posted earlier.