I had Ashcrofts fit a HP24 gearbox to my diesel way back in 2012. At their recommendation I had a boss welded on to the gearbox sump to accept a temperature probe.
At the time I bought a cheap digital temperature gauge on Ebay and cannibalised the guts. I fitted the digital panel bit into a spare space in the instrument binicle. The temperature sensor that came with the kit was a two wire thermistor type.
It has worked well for 6 years but has just failed. The temp shows 01 deg C.
I have measured the old sensor resistance and it has gone open circuit. I have now plugged a new two wire sensor in (not yet screwed into the gearbox) and the digital panel now does its startup cycle which it didn't before but then shows 130 deg C. at just ambient temp.
The new sensor resistance is about 50 ohms which does alter with temp. I tried it in boiling water. It is an NTC thermistor. Resistance drops as the temp rises. It looks physically exactly the same as the old one.
I thought that all cheap car temperature probes would be standardised, use the same thermistor and have the same range. However I am now suspecting that there are different resistances despite the ranges all saying 0-150 deg C.. Anybody shed some light on this?
I know there are single wire and twin wire types. There is no technical data included with the sensor other than it is 0-150 deg C.
I could buy another complete gauge kit that comes with a sensor so they are a matched pair but the dash will have to come out again to fit it.
One other thing: I measured the voltage to the sensor plug and it is only 5 or 6 volts. Not sure what voltage it should be from the digital head unit. It has a 12v supply to it behind the dash.