playing kill by
AO Gold Member
Join Date: Feb 2005
County: Down in the Park
78 or even 60 degrees would be plenty to heat up the car. but engine temp is only one part of the equation.
there's also outside temperature, inside temperature and the temperature of the air coming out of the vents (if you have dual zone aircon there'll be 2 of the latter ones)
check you coolant level before all else, if there's coolant present in the header tank you're fine, if there isn't you've likely found the cause of the inefficient heater.
To check the thermostat, lift the bonnet when the engine is cold (parked overnight or during the day), start the engine and feel the hose going to the radiator in front. the hose should stay cold for a long time, then suddenly get HOT. If it goes from cold -> luke -> warm -> hot the thermostat is shot.