car is a version3 sti 1996
just had a service and cars fine when driving along wether hard or normal driving , heater works as normal nice and hot , but after a while when stopped when engine running the heater blows cold and temp gauge rises to high as soon as you move on again heater blows hot and temp gauge drops almost instantly , any ideas ?
could it be thermostat ?
cheers Tk

 

Could be low on coolant or have an air lock. Was the coolant change at the service?

 

coolant looks topped up, i did think there may be an airlock but did not think it would do this , as for coolant changed im unsure i doubt it maybe they put some antifreeze in if it needed it , i'l have to phone them.

 

i have got the same problem on my bug eye wagon did you manage to find out what it was