I have read lots of information on this forum about the temperature gauge being inaccurate etc. But why? Is it the gauge itself, the sender, the wiring, the position of the sender ....what is actually the root cause of the inaccuracy?

If the sender - it could be replaced, moved if position is the issue...if it's the gauge, then what is it about the gauge - why doesn't it respond to the signal from the sender?

Thanks Allan

 

The coolant temperature is accurately reported to the engine control module (ECU) by a sensor in the cooling system. This accurate data is also available for diagnostic purposes via the OBDII port.

The accurate temperature information is then digitally transmitted to the instrument cluster. The instrument cluster then displays this information on the gauge (which is a stepper motor) by moving the pointer.

The computer in the instrument cluster is programmed to 'filter' the temperature information so that the needle stays dead center from 185 to 235 degrees F. Therefore the needle effectvely only indicates normal temperature prior to full warm up. Then it indicates normal or overheating..just like an idiot light.

Jaguar does this because they believe a moving needle will cause concern among ignorant customers.

In fact a moving needle, when understood, can give early warning of cooling system problems to educated drivers.

More information is available on my website (see address below).

 

Get the RealGauge upgrade and your temp gauge will be accurately live.
Simple to follow instructions for installation.
Best upgrade on an x308, period.

 

If the X308's temp guage is computer managed the same as in the X350's, you'll find that the needle fluctuates a needle width above and below dead center giving real-time clues when the engine is running hotter or cooler than "normal". I was able to use this subtle movement on my X350 to correctly determine that my t-stat and coolant needed replacing, before having a major problem. It is what it is, and I think more and more manufacturers are going doing the same now.

 

The X308 and X100 cluster, though computer controlled like the X350, does not indicate any subtle movements like the X350 (until about 235 degrees). The X350 uses different hardware and software in its cluster.

 

Thank you everyone, most helpful.

Anyone know where we can buy this product in the UK? I searched, however, I didn't turn up any retailers/venders in the UK yet. Many thanks, Allan

 

Allen if you follow the green link in WhiteXKR's first response to your question you will be seeing that he is the man to talk to.
Worth the money for peace of mind that you have a RealGuage.

 

I only sell direct to my customers. You can buy it here, I ship my products to the UK all the time: XK8 / XKR / XJ RealGauge - TheJagWrangler

 

Ah, I've had first hand experience with overheating on my X350 XJR.

The needle sits exactly in the middle of the gauge from 84°C up to 106.6°C, maybe even higher, lucky for me it didn't get hotter than that.

The temp gauge in the X350 is equally as useless as the one in the X308 or X100...