Vauxhall Zafira heater want get hot

If getting lukewarm heat , check thermostat .If no heat at all , check heater control cable which will either fit onto a valve or flap and see if operating or not .First thing , check coolant level .

Has the car recently had its coolant changed , if so make sure there's no air in the system , bleed the system via the little taps , look in manual it will show you were they are or check pipes are not blocked especially near back of engine leading in towards the dashboard there's also a small radiator behind there as well which where your coolant goes through to give heat to inner compartment if it's blocked you will either get only warm air or just straight cold air