During the last two weeks during my 60 km daily commute, there have been 2 instances where the temperature needle moves close to redline with the dash "overheat" message coming on. At the same time the AC blows warm air. Suddenly, the temperature gauge will reset itself and appear normal with the needle at the mid point. The AC will then cool as normal. Not sure what the problem is, but my (non technical sense) belief not to be relied upon appears to suggest a faulty thermostat. There has been no loss of coolant and everything else works. Any suggestions?

Many thanks,

Murphman

 

This does sound like an electrical problem and not an overheating problem as a faulty thermostat would not normally right itself. First thing is surely to replace the engine temperature transmitter. I had similar on my MG TF and replacement of the transmitter cured the fault of apparent overheating yet the car drove perfectly normal. On the TF there are two transmtters, one for the gauge and one for the ECU. I'm not sure what the Jaguar setup is.

 

Looking at the diagrams, our cars have 2 sensors. They are simply referred to as "Temp Sensor 1" and "Temp Sensor 2". I would suspect that one is for the left bank and one is for the right bank of the engine. I know most of the cooling system in the engine is split into 2 parts. Unfortunately, the repair manual I have is only for the 3L diesel engine which would not be of much help to those of us with the 5.0L motors.

 

I appreciate the path forward! I will follow-up. Thanks.

Murphman

 

Problem now solved. Replaced fan and thermostat. No longer any AC or temperature gauge problem at a stop or slow driving speed. New thermostat fixed the moving temperature gauge. Replacement fan only available from Jaguar dealer which is the reason for an expensive fix. Thanks for all the good suggestions.

Murphman