my girlfriend has just had here car serviced and ever since the temp gauge keeps going up and down between 90 and maximum the garage is now closed any ideas

If the coolant reservoir cap was unscrewed and not replaced tightly by garage it could have lost coolant fluid as steam and cooling system would not reach pressure for correct operation.

 

Look over engine bay for white crust, this would indicate condensed coolant antifreeze was sprayed out from a leak. Careful Don't burn yourself on hot engine

or exhaust.

 

Check the coolant fluid level is at max by looking through the clearish white plastic reservoir with large blue cap. Only unscrew cap when engine cooled (risk of scalding). Turn cap a quarter turn and wait for any hissing to stop. Top up with a universal coolant like Prestone yellow or neat VW red antifreeze.

 

Or it might be coincidental failure of the thermostat which has become sticky and is staying closed too long.

 

Or the water pump impeller might not be spinning properly or has lost a plastic blade or several to circulate the heated engine coolant efficiently. If the pump seizes it can become an expensive repair.

 

 

Welcome to the Forum.

 

I would go along with everything said in the above reply, but I would also add that, if you can't find anything obvious, using the advice given, I would suggest that you don't use the car until the garage have checked it over.

If the problem is with the thermostat or the pump and you continue to use the car, there is a strong possibility that you could do some very expensive damage.

 

Hopefully, it is only a minor problem, which can be quickly dealt with by the garage BUT the risk of continued use before it is sorted, could vastly out-way the inconvenience of not using it.

 

Regards

Thank you so much they forgot to plug a plug back in dont know which one but thanks for you advise 

coolant temp sensor not fully plugged in. Thank goodness it was only that. 

 

I should have asked about the rate of change. Suddenly high and suddenly back cool without fan would be electrical.

 

So break in contact appears to be really hot.

Ok that's one I've learnt.