Fuel guage not working.

Anonymous · Post by **Anonymous** » Thu Mar 17, 05 4:43 pm

Evenin all.
'68 Barracuda: In the cluster of four; temp, oil, amps and fuel, the fuel guage is the only one not working. The car was having some other work done on it recently by an auto-electrician and I asked him to take a casual look while it was in there and he could'nt locate the exact fault but thought it was likely to be the guage. Is there anything else to check before pulling out the dash. Thanks.

Kev · Post by **Kev** » Thu Mar 17, 05 5:02 pm

Get under the car, pull of the wire from the gauge to the sender on the tank and earth it out. (Not on the tank as this may not be earthed) If you get full deflection on the gauge it's the sender end. Check that the tank is well earthed. I had to put a jumper wire across some rubber pipe coming out of the sender to get the gauge working. Hope this makes sense. Check you have a 12v feed on one side of the gauge, also.

Alex · Post by **Alex** » Thu Mar 17, 05 6:13 pm

Whoa ! the guage only sees 5 volts, put 12 to it and the guage will fry !

I would bet the float has sunk..

MrNorm · Post by **MrNorm** » Thu Mar 17, 05 6:50 pm

Supposed to be a grounding strap to earth the tank. Mine had almost rusted away (though still worked). Might be the reason

Kev · Post by **Kev** » Thu Mar 17, 05 7:03 pm

How queer! I was talking to Blue today and he reckons the gauge sees 12v(?) I hooked 12 up to it and it deflected way past full

Can you clarify the situation please Alex. I have a (alleged) Mopar sender in me Jazz tank but my Oz gauge reads empty when full (tried swapping the sender connections, still the same), then goes up a few notches as it emptys then back to empty when it is empty. I've got an American Dart fuel gauge and was testing it by putting 12v on one side and the sender on the other. How is the gauge seeing 5v? Cheers. (If my post doesn't disappear, like a few have today.)

MrNorm · Post by **MrNorm** » Thu Mar 17, 05 7:08 pm

Usually all the dash guages run off 5V, it is regulated down in the cluster. The trouble is it is a mechanical regulator (prob some kind of bimetallic strip?) so you get a lot of hysteresis. Smart move is to replace with a readily available IC (cheap, small, and functional). I shall be doing that myself (even though I'm not smart - it's still allowed)

Alex · Post by **Alex** » Thu Mar 17, 05 7:15 pm

The back of the dash has a voltage regulator, this has three pins, 12v in, ground and 5 volts out, I had one go bad on a charger and it killed all the clocks in a puff of smoke! if the temp guage is working right the fuel guage should be fine, the ammeter works stand alone from the other guages.

If you have a voltmeter pull the wire from the sender and see what it says it should alternate between 0 and 12v, the average will be 5 volts if the loom is correct, then ground the wire with someone watching the guage, pull the wire off the ground before it reaches full deflection to prevent the needle twisting and giving false readings.

If this lot checks out, the problem is the sender, check the sender is earthed if it is, pull the sender from the tank and check the float ( it will have sunk for sure

) if it is ok (unlikely) put an ohm meter on the sender and check that the resistance changes as you move the float arm.

Fit new float

replace sender, marvel at the working guage, have a drink to celebrate (I would recommend Guiness coz of the day)

Anonymous · Post by **Anonymous** » Thu Mar 17, 05 9:05 pm

Thanks K, G and A,
Alex, if I get it done today I really would celebrate as there are only 3 hours left , 2 of which I will be at work and for the remaining one IT'S DARK OUT THERE