Temperature gauge stays at bottom then jumps to max

RaisedYaw · Post by **RaisedYaw** » 20 Sep 2023, 15:03

When the car is started, the gauge will not move for around 4 minutes and then it will suddenly jump to around 3/4 and slowly rise a little more to just below the red which is where it stays. After reading online I suspected the ECT sensor, so I decided to order a complete thermostat housing with the sensor included as I thought it also rules out a bad thermostat too. Fitted the new part and the issue persists. I'm not sure where to go from here? any suggestions?

yanga001 · Post by **yanga001** » 20 Sep 2023, 15:41

If you leave the car sitting for say 15 minutes at 20C does the gauge go to zero or stay at its constant position?

Does your radiator fan engage when it sits at 3/4 or does it cycle normally?

Diagnostic wise we have replaced a resistive based sensor so something else may be amiss.

OBD it at temp when it is at the 3/4 position. From memory my petrol one stays dead centre.

After this i think we can make a better determination. My knowledge is from the petrol engines so there may be gaps.

RaisedYaw · Post by **RaisedYaw** » 20 Sep 2023, 17:18

yanga001 wrote: ↑20 Sep 2023, 15:41 If you leave the car sitting for say 15 minutes at 20C does the gauge go to zero or stay at its constant position?

Does your radiator fan engage when it sits at 3/4 or does it cycle normally?

Diagnostic wise we have replaced a resistive based sensor so something else may be amiss.

OBD it at temp when it is at the 3/4 position. From memory my petrol one stays dead centre.

After this i think we can make a better determination. My knowledge is from the petrol engines so there may be gaps.

So after 4 mins it will jump to 3/4 then at 15 mins it would have reached a constant position just below the red. The fan has come on at idle after pushing it on a hot day but I think that's relatively normal. Otherwise the fan stays off. I tried unplugging the sensor completely which did send the kenlowe fan to come on instantly (Assume because the ECU was getting no reading from the ECT). I'm pretty confident the reading on the gauge is way off just seems to be uncalibrated or something?

When using the OBD from cold it will slowly rise unlike the guage.

yanga001 · Post by **yanga001** » 20 Sep 2023, 19:15

If the OBD2 is reading the correct ECT temperature then we can eliminate a lot of the remainder of the system.

May be an issue with the cluster itself as opposed to the remainder of the car if the car reads the correct data when checking OBD2.

RaisedYaw · Post by **RaisedYaw** » 21 Sep 2023, 13:24

yanga001 wrote: ↑20 Sep 2023, 19:15 If the OBD2 is reading the correct ECT temperature then we can eliminate a lot of the remainder of the system.

May be an issue with the cluster itself as opposed to the remainder of the car if the car reads the correct data when checking OBD2.

That was my next thought, I'll source a new instrument cluster and see if that resolves the issue. Thanks for your input, will update when the new part has been installed.