Just a quickie. The last few days my coolant temperature gauge has decided to play up for a few minutes on my drive to work. Cruising at 70mph, the gauge will gradually sink from 90 to about 65 for a few mins and then just go back up to 90 again, it did this once on the way home from work today (40 mile motorway drive). Don't think its the thermostat as its only about a year old (though I accept that's no guarantee it's still OK), am getting roasting hot air out of the dash vents and the coolant temp (from CTS?) via the climate control panel reads 90 degrees (block 51 right?) all the time the gauge is playing up....... Any ideas what might be causing this? Problem with the dash/gauge or could it be the thermostat? I'd rather it be the thermostat than an issue with the gauge or dash tbh........all other gauges eg oil temp, voltmeter,fuel etc work perfectly . Thanks!