Hi Dave,
When I purchased my RR I also had the check book symbol popping up occasionally so got a friend of mine to pop over with his nanocom and when he plugged it in it showed that the sensor on the coolant pipe behind the dash was reading incorrectly, may be your problem too. They are a doodle to change and cost around £20 from island.
Hope this helps. Paul.
so thought it was worth a punt for 20 quids plus postage but while waiting for the new sensor to arrive i checked the hevac and all seems to function ok heat goes where it should etc etc. sensor arrived fitted no difference but did find that my O rings are leaking only did them in may :doh::doh::doh:
Intermittent blowers fix and you will never guess what it was. No not that no not that no not even that...................
I have a rechargeable torch connected up in the boot only put it in recently about the time I started getting into blowers well stopped for petrol get in start it up no blowers so I unplug the torch and the blowers start up