Water Temperature reading 61 Degrees when cold in garage!

[s3dave]

I noticed my temperature sensor was overreading while sitting in the garage with the engine off. I purchases a new sensor. But before fitting I confirmed the fault, then slaved in the new sensor, both read 61 degrees. The ECU sensor was reading (off the laptop) ambient temperature at 14 degrees. With the sensor disconnected the instrument pod was reading 48 degrees. With the main bulkhead plug disconnected, the pod was still reading 48 degrees. I have checked all the ribbon connectors to the pod and they all look OK. Any suggestions? should I change all the ribbon connectors, or is there further fault finding I should be doing first?

[s3dave]

Thanks Nick. I read that from your post, and I did wonder, especially as i got the sensor from Racing Green. But the one interesting point is if I disconnect the sensor (ie open circuit) I still get 48 degrees.

Can anyone tell me what their's read on dash if the sensor is disconnected

[s3dave]

Thanks Nick. Yes ignition on. This morning with multiplug disconnected it's reading 36 degrees (with both old and new sensor connected it's reading 42 degrees).

[s3dave]

Nick. Still not fixed. You may be right, but not in the engine loom, but maybe the car loom. With the multiplug disconnected I still get a reading of 36 degrees (ie engine loom disconnected). I checked the earths and they seem ok. Not looking forward to trying to hang upside down to do continually checks under dash (or potentially remove the whole dash).

I took the car out today with my laptop connected to the diagnostic port. The car ran well with ECU water temp reading when warm around 86-88 degrees with fan coming on occasionally but the dash was reading around 97, but the delta was not consistent - 10 degrees higher when hot, but over-reading by more than 20 degrees when cold.

[s3dave]

Temp issue fixed. Just to close the loop for anyone in the future.
Symptoms: dash temperature reading over 60 degrees while car was in the garage with engine off.
Solution: Temp sensor changed but issue still present. Dash ECU was sent back to Paul Smith but No Fault Found. Since then on everyone's advice I have been looking for an earth issue. Then last month the fan would only work intermittently. I found if I pressed my thumb on the centre of the Dash ECU, the HVAC fan would work. Again dash ECU sent back to Paul Smith. He found the issue with the fan control and while again he could not reproduce any temp indication issues he change a component "on spec". Great news, the dash temp is now indicating correctly. Many thanks to Paul for a quick turnaround and repair of the dash ECU (I hope he never retires!).

Edited by s3dave on Saturday 29th April 22:47