I spent a few too many hours yesterday fighting to get my fuel guage working. I fought with rusty screws in the sending unit only to find out that it was reading perfect at 3-110ohms. Then I had to run new wires from the sending unit to the plug at the guage cluster. I thought that it would be fixed for sure. I had the sending unit set to read "full" and when I turned the key on it went to full. But when I put the sending unit to "empty" the guage stopped at half. With the key off, it goes back down to empty. So I said screw it, at least I'll know when to get gas. I put everything together and put a little less than two gallons of gas in and the guage went to full. I'm nearly positive that the problem is with the guage, but before I dive in buying parts on a hunch, I'd like some opinions.

The FSM doesn't explain testing the guage itself very well and it was no help to me. And please don't post, "Look in the FSM", I'm just asking a question to get an answer.

 

Well honestly you've eliminated all related problems besides the instrument cluster. A few times in posts it's come up that the connections behind the gauges are suspect. Try a search to find a picture.

 

The factory testing of the gauge involves disconnecting the connector from the sending unit and using their tester which applies different resistance values to the gauge. You can do the same thing by removing the sending unit from the tank, plugging the connector back in that leads to the cluster and move the arm up and down while having someone watch the gauge.

However it sounds like a loose or poor connection in the cluster.

 

I cleaned the connections at the back of the cluster and I pulled the guage out and cleaned up where the guage is bolted to the circuit board. Since I did all of this at the Ford dealer I work at, I was able to get ahold of the tester that allows you to adjust resistance. even at 110ohms on the tester, the guage wouldn't go below half. I'm still suspecting a guage problem, I might go to the junkyard next week to pick up a cluster and see if it does any good.