Topic: Inaccurate fuel gauge '65

[MattDoscher]

The fuel gauge in my '65 w/ deluxe interior and 5 gauge cluster is inaccurate.  I filled the fuel tank up but the fuel gauge only reads half full/empty.  Several months ago when I would fill up, the gauge would read full but not now.  The gauge is a new repro unit as is the fuel sending unit in the tank.  I had problems w/ the oil pressure gauge a few months ago.  It worked for a while then just started not registering at all.  I had to exchange the oil gauge for another one.  I may have to exchange the fuel gauge for another one as well.  Can the fuel gauge needle be adjusted at all to remedy any inaccuracies or not?  I have the cluster out of the car and the fuel gauge out of the cluster and it doesn't look like there is any provisions for adjustment of the needle.

thanks,

Matt

[midlife]

Please don't try and adjust the gauge needle: it almost always results in you buying a new gauge.

Did the gas gauge start reading badly after you replaced the sending unit?  There are several aftermarket sending units that have different resistance levels than the Ford original, and that just screws up the gauge.  You could also have installed the sending unit in an incorrect alignment such that the float doesn't go all of the way up on the base.  Does the gauge ever go beyond 1/2?  The sending unit could have a flat spot on the resistor wire wind.

To check that your gauge is still good, put the key in ACC, then briefly ground the sending unit wire to ground: the gauge should peg high. 

To check your sending unit, remove it and measure the resistance with the float fully down and fully up.  When up, it should read 13 ohms; when down, about 79 ohms.

[MattDoscher]

Thanks midlife for your reply and suggestions.  Well, I thought I had problems but once I started the car the fuel gauge needle slowly started to register a full tank and everything seems ok now.  I didn't do anything other than re-install what I had taken apart.  Prior to me taking the cluster out I was filling the tank using 5 gallon gas cans (left over from Hurricane Irene) and watching the fuel gauge needle move w/ the key in the Acc position.  I guess the battery alone doesn't provide enough juice to fully register a full tank of gas until you crank up the car?!

[midlife]

Battery voltage shouldn't matter, so long as it is above 6V.  The constant voltage regulator on the back of the dash is a fast-acting circuit breaker, so the average voltage is 5-6V; the circuit breaks when the bimetallic metal strip heats up and bends away from the contacts.  It does take a few seconds for the dash gauges to get up to speed, however.

You might consider replacing the CVR and check the grounding point on it as well.

[MattDoscher]

Thanks midlife.  What are your opinions about the new electronic CVR's as an alternative to the standard CVR?  What do you think about the new LED bulbs for the gauge lights?  Money well spent or should I just stick w/ the regular CVR and bulbs?

[midlife]

Both are good upgrades.  The LED's, though, do change the basic color once the light passes through the diffusers.

[MattDoscher]

ok, thanks midlife.

Matt