! The heater is not blowing hot after the engine has warmed up.
! There is an odd smell in the car when you turn on the heater.
! The fan doesn’t work or only works in one mode.
! You detect a coolant leak.
! The system is noiser than usual and makes cracking or popping sounds.
Main reasons for failure and how to identify them
Air lock or low coolant level. Park your car on a flat surface and let the engine cool down. Open the bonnet. Remove the cap of the coolant expansion tank. Check the coolant level and top it up if necessary.
Faulty thermostat. Start the engine. Check the lower radiator hose as soon as the temperature gauge starts reading more than zero. It should be cold. If it heats up immediately, there may be a thermostat issue. Check the lower radiator hose when the coolant reaches 85°C. It must be warm to hot. If it’s still cold, your thermostat must be defective.
Clogged heater core and piping. Clean the heater core of dirt and foreign matter. Remove the heater core and rinse it with a special agent.
Faulty blower motor. Check the electrical circuit, especially the contacts. Make sure the heater blower brushes and bearings are not worn out.
Faulty heater control valve or heater flap. Visually inspect the heater control valve or the heater flap. If you notice that the control valve lever is corroded, the rubber gaskets are dried out, or the heater control valve or the heater flap are worn out, replace these components.
a smiley technician with plenty of experience starring in AUTODOC's video tutorials; Never seen without his goggles; races his BMW X5 E53; dreams about receiving a Gold Play Button for getting 1,000,000 subscribers on YouTube.