hi everyone ive got a 190e 1800cc and the heater will only blow hot air and not cold can any one help please thanks kerry

 

Check the heater valve, referred to as a mono or duo valve. You will have a mono valve. It is the heater valve that controls coolant flow to the heater core. Over time, the insert seal tears and coolant bypasses, allowing heat at all times. Chances are that it is the insert (if avail separately) but the coils on the valves are known to occasionally go bad too(complete valve). Easy way to check it is to pinch off the outlet of the monovalve (inlet of heater core) which cuts off coolant to the heater core and see if it gets better. If it cools down, that will likely be the problem.

 

thank you for your info i hope it works thanks ,kerry