Audi Workshop Service and Repair Manuals > A3 Mk2 > Heating, ventilation, air conditioning system | Auxiliary heating | Aux. heater/heater booster | Incorporation of auxiliary heater into coolant circuit

Non-return valve in coolant hose

Note

t	Non-return valves may be fitted in various coolant hoses depending on the vehicle equipment → Electronic parts catalogue. These non-return valves are not always visible from outside.

t	The following illustration shows a non-return valve-A- fitted into the coolant return hose -B- (from air conditioner heat exchanger to engine). The -arrows- indicate the coolant flow direction

t	The non-return valve function can be checked using, e.g. compressed air. Do this by carefully blowing compressed air through the removed coolant hose, first from one side and then the other.

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