Non rallye fuel gauge accurate??

[lee01]

What you guys can tell me about the non rallye fuel gauge from a Duster?

Is it reliable or accurate?

I have a new fuel sending unit, gaz tank, and new wiring.....so beside the gauge itself and the circuit board, everything else will be new.
Circuit board and pin look fairly good and no damage.

Do you guys think the 40+ years stock gauge will be fine and accurate?

 

[67Dart273]

It's a crap shoot. Any "precision" instrument that old is subject to suspicion, but you CAN check gauge accuracy. Go down to Radio Shack and get some resistors, and substitute them from the sender wire to ground. You can check the temp gauge the same way. Checking both gauges also gives you an idea of the limiter accuracy -- as say, both gauges read off by the same amount might be the limiter rather than both gauges.

You need to be sure the board connections are good, including the gauge studs and the socket for the limiter, AND make sure you have a good limiter.

The info I have is

L = 73.7 Ohms (empty)
M = 23.0 Ohms (1/2)
H = 10.2 Ohms (full)

So about 25 ohms will give you a 1/2 scale reading, example.


Also, opinions are that most some of the repop senders seem to be less than good. Some guys have diddled them by bending the arms, and adding a little bit of series resistance to get the range of reading right, IE many of the repops seem to NOT want to go to full, after getting the empty end reading right. This is a sender design issue.

 

[RedFish]

There is also a voltage limiter for the gauges.
As for accuracy.. These are not gauges. They are range indicators at best. You should expect a gauge to show full when the tank is full and empty when the tank is empty. If it shows full after you know a few gallons have been used, thats normal. If it shows empty and less than tanks capasity is needed to fill it, thats normal also. Bottom line, everything between the end limits of the range is wide open.
When do you know for sure a range indicator needs service ? When it shows you have better than empty yet run out of gas.
Water temp and oil pressure gauges should be of more concern since their false report can result in serious engine damage.
You can have all of them inspected and qualified for continued use, along with OEM accuracy for as little as 15 USD each. Hope this helps