Gas Gauge Problem

[Irish Wake]

1988 K5 Blazer

Gas guage was stuck way above full. I dropped the tank and the metal cover that covers the end of the float arm had come loose. I reattached it and tested it with a 12V test light. Bright on Empty Dimmer on Full. Put everything back together and now the guage reads 1/2 when tank is empty and a little past full when full.

The guage doesn't bounce and did go to Empty when I grounded the sender wire.

Any suggestions? Thanks

 

[shaun89]

maybe your sending unit isnt resisting enough and just keeping the needle too high, even though it went dim, it might not be enough. im not a big electronics person, but i know most chevy gauges read 0-90ohms, maybe you have a multi-meter or something that can check the resistance on the gauge from the sending unit. it might be reading only say....45 ohms so i will only go down to 1/2 and not resisting the full 90ohms to go to empty. i hope this helps.

 

[pvfjr]

You're reading too much resistance, as opposed to too little. Your tank might not be grounded properly, or your sender wire might have a bad connection somewhere that's adding resistance to the circuit. Sounds like the guage is fine, you just gotta figure out how to send it the right signal. Here's some random info I put into a PM once, hope some of it might help. I don't feel like rearranging it to suit your specific problem at the moment, but there's some info in there nonetheless.

Well the good news is you have the simplest setup possible, dual tanks really complicate things. The basic operation of the gauge is fairly simple. The sender is just a variable resistor of sorts. The gauge measures the resistance to ground, through the sender. So the gauge has three terminals: one ground, one accessory positive, and one to the sender. As you fuel tank empties, the sender should decrease it's resistance, so that terminal on the gauge will approach ground. If your tank isn't grounded properly, the sender wire becomes a path to nowhere. A bad ground can cause what is known as an open, or it can add unwanted resistance in series with the circuit. An open will cause the gauge to read well over a full tank, so long as the gauge is powered up properly. Unwanted resistance added in series with the circuit, however, can just cause the gauge to read too high. Another cause of an open condition, could be a bad connection to the sender. The wire could be broken somewhere, or have a bad connection where it passes through the firewall in the bulkhead. This can cause you to run out of gas when you still read 1/4 tank, for example. If the gauge is stuck on empty, it is likely that the sender wire is shorted to ground somewhere between the tank and the gauge.