Fuel gauge

[mt308]

Hi

This is probably a really basic question...

Trying to calibrate my fuel gauge. When full I get about 7 ohms of resistance. Empty seems to be about 180 ohms or so. This is taking a reading between the sender unit and an earth connection.

BUT when I turn the ignition on the readings go crazy. The empty tank shows infinite resistance (i.e. I can't get any reading at all) and the full tank shows about 165ohms.

Is this normal, or might I have some sort of short circuit going on.

Am I taking readings between the right wires?

As it stands my fuel gauges are not accurate - they read full when full, but when they lose about 10 litres they read about 1/4 full.

I have standard VDO tube sender units, Ultima supplied.

Thanks
Mark

[mt308]

Thanks all

I have the gauge wizard which I have to date nstruggled to calibrate. However I think I will add another earth connection as I have 4 spade connectors on the back of the fuel gauge which might be too much....

Have just taken readings for a standard 40 litre Ultima tank which were as follows from a VDO sender unit.

Empty 73.8ohms
1/4 65.4
Half 51.7
3/4 29.0
Full 9.8

Will let you know if I can calibrate using the wizard. Ran out of time tonight.

Mark