Heater stays on

[gnj588d]

My friend has a W112.He has a problem with the heater in that it stays on even when set to cold, not very nice during our heat wave
has anyone got an idea what might cause this, the cables are all still connected  ???Many thanks .Mike.

[wwheeler]

A W112 is a 300SE versus a W111 220/250 SE. I would assume the heater valves are the same as my W111 280SE. The cabin heat is controlled by two valves that are just below the center of the dash. If you have a/c, it will be harder to see. These valves control the flow of hot coolant through the heater cores. I am sure the only way you are getting heat is because these valve(s) are not shutting off. It is common for them to be corroded up and difficult to turn. The other option is the cable connection at either end could be loose. In which case the cable and lever will move, but the valve won't.

So check the cable connections first and then look at the heater valve. With no a/c, the valves are easy to clean and replace the o-ring seal. BTW, the o-ring is metric. DO NOT use an english size as it will bind!!!!     

[GGR]

all what wwheeler said. But sometimes, after having done all that, the heat still does not shut completely. Rather that re-dismantling everything, I installed a very sophisticated climate control device: I ran to ACE hardware store, bought a tap and installed it in one of the heater hoses in the engine bay. Not the best looking, but at least I have no more heat coming during the heat wave!

[gnj588d]

Thanks for the reply try it at the weekend. Cheers .Mike.