Temp Gauge - stuck on cold

[BlackhawkSaab]

Hi,

The '98 S-reg 9-3 convertible I bought a few months ago came with a few niggles which were fine considering the age and price.

For weeks the temp gauge on the dashboard has been intermittently moving from '9 o'clock' to cold and back again. In the last few days it has remained stuck on cold whatever and is showing no signs of moving. I know this doesn't read the 'real' coolant temperature but any thoughts on where to look for faults and what might need replacing.

Similarly - Since I last filled up with petrol I have been getting odd range and DTE read-outs from SID. After a couple of thousand miles of indicated 31-32mpg SID is now over reporting the mpg (36-ish) but conversely under reporting the range (c.300 miles when full). The fuel gauge is about where it should be for miles done. Does anyone have ideas about this? No settings on the SID have been changed.

Many thanks!

[Audax]

I'd suggest that it's the coolant temp sensor has failed, it's not an expensive part and I'd suggest replacing it along with the thermostat. The most likely reason you're getting strange readouts on the SID is that the engine ECU can't read the temperature of the coolant so it will be pumping more fuel into the engine.

[BigMike]

For weeks the temp gauge on the dashboard has been intermittently moving from '9 o'clock' to cold and back again. In the last few days it has remained stuck on cold whatever and is showing no signs of moving. I know this doesn't read the 'real' coolant temperature but any thoughts on where to look for faults and what might need replacing.

I had this on my S-reg convertible.  It was the temp sensor.

Regards,

Mike

[BlackhawkSaab]

Thanks - took a couple of weeks to get around to this but temp sensor and thermostat replaced and dashboard needle back in the middle of gauge.

Thanks!

[dw]

I had a similar experience, after getting a new sensor and thermostat fitted the car ran smoother and I think it used less petrol.