I'm sure someone had this problem, and maybe you can enlighten me on this

I have a 1972 duster with the standard dash cluster, and the problem is that the gas gauge is showing less gas than I actually have in the tank. I have a new sending unit, and ohmed it and it seems to be working correctly. I have 3/4 tank of gas in the tank and the dash gauge is showing me with only 1/4 tank left. At this point it ohmed out at 27 ohms. which it should be showing about 3/4 tank..Correct me if I'm wrong,,75ohms is full and 10 ohms is empty?. I checked the ground strap on the line on the sending unit, and I even ran a second ground, and still no acurate reading. What else to look for? Can it be on the dash cluster itself?

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Brian Long

Check your voltage going into the gauge. IIRC it should be ~5 volts. You might not be getting all the voltage your gauges require due to the voltage limiter being only 30 something years old, the wiring in that circuit isn't up to par, or it could be internal resistance on the gauge itself. Where are you testing the resistance of the sending unit at?

Check it at the instrument cluster connector (purple I believe) and see if your reading is the same.

~RDE~

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1984 D100 Shorty Custom
Certified Auto Appraiser - RevItUp Classic Appraisals
President - Cherry City Bombers CC
Part of Tyrde-Browne Racing

Unplug the gage at the tank, ground out that wire from gage, and see if the gage reads full. If not, you have a voltage / resistance problem in that circuit.

If gage reads full, you have a calibration problem with the sending unit. Could be a float adjustment issue, or a fuel logged float

Also some of the after market sending units are 12 volt, not 5 volt, and will cause false readings with Chrysler gage.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

i talked to the Dwayne at Vans, where I bought the sending unit, and he's telling me that 10 ohms is full and 75 ohms is empty.I though the same thing about the float adjustment, but he says 27 ohms is going to read about 3/4 tank. I going to ground out the gauge wire at the tank and see if the gauge reads full. thanks for your input.

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Brian Long

i was testing the ohms at the tank, and it gave me 27, which should be about 3/4 tank, but im showing 1/4.

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Brian Long

Right, now you check the same wire where it meets the cluster and see if you get the same.

Does your temp gauge work?

~RDE~

_________________
1984 D100 Shorty Custom
Certified Auto Appraiser - RevItUp Classic Appraisals
President - Cherry City Bombers CC
Part of Tyrde-Browne Racing

I would check that the tank is really grounded; ~50% of the time I've seen a gas gauge read low or not at all, the little tank strap from sender to fuel line was broken or missing.