Thread: Electrical Problem- Gauges all over the place

Originally Posted by slug_burner

FIrstly I would ensure that the gauges are ok or rs. Having got the gauges out I would put them on a bench with a linear pot (not log) to ensure that you getting a good range acroos the pot. Also check what the resistance of your fuel and temp senders are and match your pot as close as you can other wise you will also lose range.

When your measuring the sender resistance do it both from the wire at the dash and then do it at the sender bypassing the wiring. You should get the same readings if all is ok.

Other technique is to compare with a known good vehicle.

After that you either need some new gauges or you need to find the fault in the vehicle wiring.

Hey mate,
This is what i did and regardless of the resistance across the 500Ohm pot (linear) the gauge was climbing. It would just climb faster as the resistance was increased. The pot was between the second pin (not 12V) on the gauge and ground. I have no idea as to how i could lose 2 gauges....

Originally Posted by slug_burner

John,

Are you saying the case of the gauge has to be earthed?

Yes! That is exactly what I am saying! I found this out years ago - replaced the sender to correct a gauge problem - it didn't fix it, eventually turned out to be the earth wire from the gauge being loose where the wire was with a stack of other earths on the speedo mounting screw.

John