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Car Water Temperature Gauge Again

Thread starter #1
Hi Guys

I’m back again with my water temperature gauge problem, since I last wrote to you I’ve taken the instrument cluster to a repairer apparently, there were some dry joints which they fixed.

On trying the gauge again using a potentiometer it works, I can see the needle move up and down as I vary the resistance but not so when connected to the sensor unit.

I have really tried to buy a replacement here in the UK but nowhere seems to stock them any longer.

I don’t want to fit a used one if I can help it as it’s a bit of a pain having to strip the inlet manifold off each time to allow access to the sensor.

I thought maybe I could fit a different sensor as long as the thread was the same as the existing one, but I guess I can’t simply fit any old sensor as it would need to be compatible with the gauge itself.

Is there any way I could physically find out what resistance the sensor would need to work at in order for the correct temperature to show on the gauge, do you have any ideas?

Unfortunately, there is no workshop manual covering the Vauxhall Omega 2.5TD and even if there was I don’t know if that type of information would be in it.


Well-Known Member
Most Helpful Member
On trying the gauge again using a potentiometer it works
Using the same test voltage as the cluster uses (5V?), measure the resistance values corresponding to zero, half-scale and full-scale on the meter. Those values will give some guidance for selecting an alternative sensor (NTC thermistor?).


Well-Known Member
Most Helpful Member
I substitute a pot (rehostat) for the sensor, set the pot to get zero, 1/4, 1/2, 3/4, and full scale, disconnecting and measuring the resistance of the pot at each point. You will need a pot that is about 500Ω full-rotation.
Thread starter #4
Hi Guys

Thanks for the lowdown, I haven't got around to trying what you've told me, but as soon as I do, I'll post back and let you know how I get on.

Thanks again


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