Mercedes-Benz C-Class W202 - Heater only warm on one side - jonny10buds

I have a 1998 R C200 Elegance without air-conditioning. It has a split heating system for each side of the interior controled by two thumbwheels, even when both are turned to hot I'm only getting heat on one side of the car, any ideas?

Mercedes-Benz C-Class W202 - Heater only warm on one side - elekie&a/c doctor

The split heating system on these is controlled by an electric "duo-valve".It is situated in the engine bay by the brake servo.It is possible that one of the diaphragms has seized closed ,thus no water flow.hth

Mercedes-Benz C-Class W202 - Heater only warm on one side - jonny10buds

Thanks for that, I had a look on one of the Merc forums and there's a lot of talk of duo valves, got in the car at lunchtime and now the heater is toastie warm on both sides, typical! Thanks again, John.