You may have a clogged heater core so do a heater core flush and unclog it.
Audi tt heater core flush.
Here s how to flush it out.
You can use regular water from a garden hose with the caveat that you shouldn t subject the core to a great amount of water pressure as this can damage it.
Is your heat not working or is your heater not hot.
Flushing the heater core isn t completely unlike flushing your cooling system during a coolant change except that it focuses exclusively on the heater core itself.
Turn on the water flow not too hard as the heater core is a bitch to replace and watch the gunk come out.
How to flush the coolant antifreeze in a 2004 audi tt quattro 1 8l 4 cyl.
Reverse the hose and forward flush again making sure the water coming out is clear.
Sometimes corrosion in the cooling system can clog the heater core.
Keep flushing until the water coming out is clear.
Audi tt 2000 06 audi tt quattro 2000 2006 radiator and hose replacement.