I'm trying to diagnose a funky fuel sending unit situation. At first I thought it wasn't working at all, since the gauge was staying pegged full. After pulling the sending unit and doing an ohm check across the range of the arm, I found the ohms to range evenly from about .6 at what would be empty to about 99 at full. After connecting it and watching the gauge while moving the arm, I found that it would go to empty on the gauge with the arm at empty position, but go to full at less than a quarter tank position. 10 ohms was full. So basically if I don't do anything the gauge will read full until it gets down to under a quarter tank and than go from full to empty on the last quarter. I recall experiencing that with a different bus in the past.
I found about 8 volts in the wire to the sending unit. I pulled the gauges and found the wire from the gauge to the sending unit and tested ohms and found 0 ohms, so the wire is good. I tested the voltage inputs to the instrument panel and found two inputs at batter voltage (12.45V). Are there only two voltage inputs?
So all I can figure is it's either
- bad gauge or loose wire inside the instrument panel
- wrong sending unit and I need a unit that ranges from 0-10 ohms instead of 0-100
- the instrument panel is sending 8 volts and should be sending 12 volts through the gauge to the sending unit.
2003 international 3800 w/ 7.3 engine, fwiw.
any ideas?