NEW sending unit in tank . Seems to calibrate out the proper ohms . Gauge is a smidge above empty with 6 gals of fuel in the tank . When i fill up the tank gauge reads 7/8 full and in 20 miles gauge drops down to a quarter tank. I installed another used gauge of another dash same exact thing???? What is going on!!!!
Fuel Gauge Help!
- Thread starter lucahemi
- Start date
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OwdKasd
Well-Known Member
Possible Instr panel Voltage regulator. How's the temp gauge? Here's a link to a good thread that may help you.
http://www.forabodiesonly.com/mopar/showthread.php?t=195049&highlight=fuel+gauge
http://www.forabodiesonly.com/mopar/showthread.php?t=195049&highlight=fuel+gauge
67Dart273
Well-Known Member
This seems to be a problem with repop senders, but it doesn't mean it's the ONLY cause
You could have a problem in several areas.
1 Wiring problems, IE resistive connections from the sender (and tank ground) up through the gauge, VR, harness, and power
2 Gauge itself could be out of cal
3 VR could be outputting improper voltage.
One way to check all this is to get down to RadShack and buy some 1 or 2 watt resistors, or combinations of resistors, to make up test resistances. This is what was in the old mopar gauge test tool.
The resistances for either temp or fuel (and I guess optional oil, some models) are:
L = 73.7 Ohms (empty)
M = 23.0 Ohms (1/2)
H = 10.2 Ohms (full)
Something I found on Mopars was somewhat different:
The resistor values are 78.5 ohms for the low reading, 21 for the mid reading, and 10 for high.
BUT you said:
Just how did you determine this?
You should be able to drain the tank down to MT and read the sender with a meter, but make sure the car is level. Then fill the tank and take THAT reading.
Six gallons is an awful lot for an "empty" reading.
You could have a problem in several areas.
1 Wiring problems, IE resistive connections from the sender (and tank ground) up through the gauge, VR, harness, and power
2 Gauge itself could be out of cal
3 VR could be outputting improper voltage.
One way to check all this is to get down to RadShack and buy some 1 or 2 watt resistors, or combinations of resistors, to make up test resistances. This is what was in the old mopar gauge test tool.
The resistances for either temp or fuel (and I guess optional oil, some models) are:
L = 73.7 Ohms (empty)
M = 23.0 Ohms (1/2)
H = 10.2 Ohms (full)
Something I found on Mopars was somewhat different:
The resistor values are 78.5 ohms for the low reading, 21 for the mid reading, and 10 for high.
BUT you said:
Just how did you determine this?
You should be able to drain the tank down to MT and read the sender with a meter, but make sure the car is level. Then fill the tank and take THAT reading.
Six gallons is an awful lot for an "empty" reading.
2 gauges, both over 40 yrs old, do the same thing, no surprise. I've been inside over 100 of these SW gauges.
Inside the gauge is a bi-metal strip that bows when heated. That bow action moves the needle. The heat comes from a electrical current passing through ni-chrome wire wound around the bi-metal.
That wire is/was insulated with a silk-fiberglass blend that was originally a pale yellowish color and very fine/thin.
I often find a bow in the bi-metal at room temperature meaning its temper is weakened.
I often find the winding coated with a black crunchy collection of crap that makes it look 5 times its original size. I think the very worst examples were in a smokers car. Anyway...
All of these age related faults effect the needle motion. Nothing lasts forever
Inside the gauge is a bi-metal strip that bows when heated. That bow action moves the needle. The heat comes from a electrical current passing through ni-chrome wire wound around the bi-metal.
That wire is/was insulated with a silk-fiberglass blend that was originally a pale yellowish color and very fine/thin.
I often find a bow in the bi-metal at room temperature meaning its temper is weakened.
I often find the winding coated with a black crunchy collection of crap that makes it look 5 times its original size. I think the very worst examples were in a smokers car. Anyway...
All of these age related faults effect the needle motion. Nothing lasts forever
Yes , The sender is close to the specs you listed. The sender seems to be fine as far as meeting the chart you posted . How does one compansate for a tired gauge. I thought I could bend the float to get the gauge a little closer
67Dart273
Well-Known Member
Contact the guy above ya LOL
But before you do that, unless you already did, I'd sure go clear through the wiring, from front to back, and make sure you have
1 Solid 12V to the voltage limiter (Make a long jumper, run from battery stud on start relay to your meter, the other meter probe on the IGN feed to the limiter) and check voltage drop
2 Make sure you have a good quality limiter. ALSO make sure the "socket" for the limiter is actually making contact with the PC board. Mine was NOT and I had to solder short jumpers from the brass contact fingers to the board
Make sure the harness connector pins to the board are tight and clean
Make sure the gauge studs are making contact. Loosen/ tighten the nuts several times to "scrub the connections" You can also check with a meter from the studs to the board for both resistance and voltage drop.
3 With the sender confirmed to be at the listed "full" resistance, if the gauge is wrong, then it's the gauge
But before you do that, unless you already did, I'd sure go clear through the wiring, from front to back, and make sure you have
1 Solid 12V to the voltage limiter (Make a long jumper, run from battery stud on start relay to your meter, the other meter probe on the IGN feed to the limiter) and check voltage drop
2 Make sure you have a good quality limiter. ALSO make sure the "socket" for the limiter is actually making contact with the PC board. Mine was NOT and I had to solder short jumpers from the brass contact fingers to the board
Make sure the harness connector pins to the board are tight and clean
Make sure the gauge studs are making contact. Loosen/ tighten the nuts several times to "scrub the connections" You can also check with a meter from the studs to the board for both resistance and voltage drop.
3 With the sender confirmed to be at the listed "full" resistance, if the gauge is wrong, then it's the gauge
Gauge itself should have a resistance of about 12 ohms plus or minus a couple ohms. Higher than 12 the lower it reads.
I put in a new sender.....correct ohms
Installed a new Auto-meter gauge under the dash...correct ohms
Installed new ground strap.
I fill her up and the gauge goes to full
Drive 50 miles or so and the needle is at 1/2 or a little below.
Drive another 25 or 30 miles and she is less than a quarter.
Stays there for a long time. Fill it up when it hits 1/8 of a tank
and it only takes 9 or 10 gallons.
The only thing I didn't replace was the wire from front to rear.
Installed a new Auto-meter gauge under the dash...correct ohms
Installed new ground strap.
I fill her up and the gauge goes to full
Drive 50 miles or so and the needle is at 1/2 or a little below.
Drive another 25 or 30 miles and she is less than a quarter.
Stays there for a long time. Fill it up when it hits 1/8 of a tank
and it only takes 9 or 10 gallons.
The only thing I didn't replace was the wire from front to rear.
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