Series 3 Temp sensor

Good afternoon ALL,
I have a series 3 109 safari on a V reg petrol that is nearing completion of full re build.

The engine temp sensor is reading sky high as soon as the mechanic puts the key in. Has anyone experienced this and if so is there a fix. The temp sensor is brand new.

Many thanks in advance.

Anton

Do you still have the old one or better still another known good one to swap out and check?

Has the wiring been disturbed? If the new sensor is ok, it sounds like ther may be a short, possibly behind the instrument pod.

Col

Good evening chaps, thanks both for your answers. Old one is a no. I'd assume the wiring has been disturbed it's had the dash out and everything. I'll relay these messages to the garage tomorrow.

Ps this is the 2nd one... So your probably right. Wiring fault

The temperature sensor is a variable resistor to ground, so if the meter is going to maximum deflection, then it suggests there is a break in the wiring either from the gauge to the sensor, or from the sensor body to ground (probably less likely, assuming the engine is well grounded). Your could short the sensor wire to the engine block/chassis to see if that makes any difference, but if the dash has been out, my money is on the wire being detached at the gauge end.

Good evening Megan's,

Many thanks for the indepth answer. I will also forward this one to the Mechanic straight away. I'll let you know the outcome.

I would think that the best way to check the wiring would be to disconnect the wire from the sensor and carefully isolate from any earth, if the gauge still does a full scale deflection then the wire to the sensor is trapped or shorted to earth somewhere in its journey from the gauge to the sensor. There are historical posts on the site relating to fuel and temp gauge issues some involving faulty voltage stabilisers but this would effect the fuel gauge as well.