Fuel gage adjustment using a resistor?
Thread Starter
Burning Brakes
Joined: Apr 2009
Posts: 1,185
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From: Charlotte Michigan
Fuel gage adjustment using a resistor?
My fuel gage upon fill up showed 7/8 full when it was just over 1/2 full as it took nearly nine gallons. I have in the past cleaned the sending unit but always had that differential of nearly half of a tank. Can a resistor be added to the wiring perhaps at the connector area where the wires come from the tank to the harness going to the front of the car so it would read lower? What size should it be and would it be just on one wire in the circuit?
Melting Slicks
Joined: Jan 2014
Posts: 2,192
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From: Lunenburg MA
Before you do anything drastic you should have sure the sender is off with an ohmmeter.
It should be <10 ohms empty and >80 ohms full (0-90 is the full range). To test the gauge short the sender wire to ground, it should empty.
You can put a resistor between ground and the sensor wire to make it read lower. You might want to use a 500 Ohm or 1K potentiometer (use the center and one of the outside terminals) so you can adjust it. Radio Shack should have this. You should be able to make it read empty when empty, but it will read even less when full.
It should be <10 ohms empty and >80 ohms full (0-90 is the full range). To test the gauge short the sender wire to ground, it should empty.
You can put a resistor between ground and the sensor wire to make it read lower. You might want to use a 500 Ohm or 1K potentiometer (use the center and one of the outside terminals) so you can adjust it. Radio Shack should have this. You should be able to make it read empty when empty, but it will read even less when full.
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
What I did was pull out the sender assembly and bend the float arm to get the gauge to read empty when the arm was all the way down. I really don't care what it reads when the tank is full -- it's empty that I want to know about.
You could try moving the float arm from one extreme to the other and make sure the gas gauge follows. Note that the response is highly damped (to prevent the gauge from jumping when the fuel sloshes around in the tank) so it takes several seconds for a change in the fuel level to appear on the gauge.
You could try moving the float arm from one extreme to the other and make sure the gas gauge follows. Note that the response is highly damped (to prevent the gauge from jumping when the fuel sloshes around in the tank) so it takes several seconds for a change in the fuel level to appear on the gauge.
Le Mans Master
Joined: Aug 2007
Posts: 8,735
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From: WV
What I did was pull out the sender assembly and bend the float arm to get the gauge to read empty when the arm was all the way down. I really don't care what it reads when the tank is full -- it's empty that I want to know about.
You could try moving the float arm from one extreme to the other and make sure the gas gauge follows. Note that the response is highly damped (to prevent the gauge from jumping when the fuel sloshes around in the tank) so it takes several seconds for a change in the fuel level to appear on the gauge.
You could try moving the float arm from one extreme to the other and make sure the gas gauge follows. Note that the response is highly damped (to prevent the gauge from jumping when the fuel sloshes around in the tank) so it takes several seconds for a change in the fuel level to appear on the gauge.
with Cliff.. This is the way we have been doing adjustments for years for gas gauges not reading correctly .. My bassboat got the same fix and it now reads perfectly...
...WW
Team Owner
Joined: Sep 2003
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Well we do it a little differently and I always thought this made "good sense". With a half of tank of fuel adjust the arm to be accurate. If it confirms half tank consistently then you can assume "maybe" that from half to empty it should be reasonable accurate.
Check first the range of the rheostat to confirm it's operational, maybe clean it and then do the half tank check. Check the dash unit also with a confirmed potentiometer for it's accuracy also. I's not always the fault of the tank sender.
Check first the range of the rheostat to confirm it's operational, maybe clean it and then do the half tank check. Check the dash unit also with a confirmed potentiometer for it's accuracy also. I's not always the fault of the tank sender.
Team Owner
Joined: Sep 2003
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