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Old 09-26-2010, 04:15 PM
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Fuel Gauge reading wrong

My 32 Plymouth with SBC power has Classic Instruments in dash. Fuel gauge reads between one-quarter and one-half tank of fuel all the time. I know the tank is full but still reads between 1/4 and 1/2. It was same way with previous gauge that I replaced. I have checked grounds, power, sender, wiring, and have even hooked up another sender (holding it in my hand and moving float up and down) as test and still get the same reading. I am baffled. Anyone have an idea what is causing this odd reading in my fuel gauge?
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34jeff

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Old 09-26-2010, 04:59 PM
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Quote:
Originally Posted by 34jeff
My 32 Plymouth with SBC power has Classic Instruments in dash. Fuel gauge reads between one-quarter and one-half tank of fuel all the time. I know the tank is full but still reads between 1/4 and 1/2. It was same way with previous gauge that I replaced. I have checked grounds, power, sender, wiring, and have even hooked up another sender (holding it in my hand and moving float up and down) as test and still get the same reading. I am baffled. Anyone have an idea what is causing this odd reading in my fuel gauge?
Thanks.
34jeff
Matching the gauge and sending unit is usually the problem. Sounds like you may need to make an adjustment to the gauge. Some gauges have a adjustment on the back. First see if the guage will read both empty and full.
Do this by removing the wire hooked to the sending unit at the sending unit.(creating an open circuit) your gage will read either full or empty then touch the sending unit wire to ground (creating a closed curcuit)the guage should read opposite. this prodeedure must be done with the key in the on position. Note a full sweap of the gauge should be seen. If you have a full range on the gauge you have a good gauge and need to adjust the sensitivity (Ohmns) if possible or need a compatible sending unit. If you don't have a full sweap the gauge is no good. If it reads backwards full instead of empty you have the wrong sending unit for the gauge. A very common problem. Hope this helps.

Last edited by CQNRQY; 09-26-2010 at 05:04 PM.
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Old 09-26-2010, 05:19 PM
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check the vendor

When I bought gages a while back I remember there are different ohm ratings from different companies for the sending units Call classic and check to see if you have the right one.
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Old 09-27-2010, 03:28 PM
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Classic Instruments make 6 different gauge resistance ranges to match several different OEM senders and an aftermarket gauge/sender set.
You will need to determine the resistance range of the your sender to see if the gauge is matched. I expect the gauge is marked with the resistance range. Such as; 0-30, 0-90, 16-158 ohms. Stroke the sender from full to empty and measure the resistance with an ohmmeter. Some sender/gauge sets read low to high ohms and some high to low ohms.
More info is on www.classicinstruments.com . Click on the tab - gauge information then types of gauges then fuel gauges and tank senders.

vicrod
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