temperature sender and gauge.

[Aussie John]

Trying to get a reasonably accurate temperature gauge. [early 94 griff black-rimmed gauges with white faces] Changed the sender which made it read worse [ both reading under ] I measured the senders in hot water and found that they went from 100 ohms at 50c to 20 ohms at 100c. I put a variable resistor from the lead off the sender and found that the gauge needs 20 ohms at 50c to 7 ohms at 100c. I am confused, any comments welcome, cheers, John.

[bobfather]

Adding a resistor is like taking the pointer off and putting it in the right position. It is often the case that there is a range error too. When we fit resistors to the Rover gauge mod we set the pointer to read correctly at normal running temperature. The rise and fall periods are highly inaccurate anyway because the sender takes a considerable time to heat and cool so during heat up and cool down cycles you're not seeing real coolant temperatures anyway.

[Aussie John]

It seems that I might need a resistor in parallel because the gauge is not reading high enough but I guess the gauge could be faulty, I think you're right about only needing it accurate near operating temperatures. Thanks for the thoughts, cheers, John.

[N7GTX]

If you need to have the gauge checked then I'd recommend ETB Instruments who can check/repair the early type gauges (black rim). Repaired my speedo in 5 days. Worth a call as very knowledgeable.