Water temperature sensor or gauge not working

Hi, 1993, Defender 200Tdi, have see the gauge move off the min stop a couple of times in two weeks!
Engine warms up okay and heater works as expected (gentle waft of warm air with full fan!).

Questions, can I check the gauge or temp sensor works? Resistance of temp sensor (engine cold) is 5.5K ohms.
Does the resistance go up or down with temperature rise? I don't want to by a sensor for £20 just to find out its the gauge.
PS battery and fuel gauges work ok

Your gauge/sender is old and they are known for unreliability. Fit a TIM 32mm capilary gauge and actualy know what the temp is in numbers.Can be had for about £35.

Earth the wire of the sensor and see if gauge goes fully up.
Might be thermostat stuck open.

Gmacz said:

Earth the wire of the sensor and see if gauge goes fully up.
Might be thermostat stuck open.

Click to expand...

Second this, easier to check the gauge than the sender. at least it when narrows the problem down.

I would put my money on the sender needs replacing.

+1 for mechanical gauge