My heater is working on one side only. There is some heat coming out of the passenger side vent and defrost. The drivers side is blowing cold, vents and defrost. I've replaced the mono valve and the auxiliary water pump but that didn't help. I opened up the lower dash area and tried manually activating the vacuum valves but there was no change. Is there a flap or valve that would prevent air flow to the drivers side? It's cold here in New Hampshire so I really need help!

Hi 3eagles,

I've attached a link to a tech article that I think you'll find helpful to your fix. Best of luck!

Climate Control Replacement - Pelican Technical Article - Mercedes-Benz W123 - Climate Control Replacement


-Dmitry