Hello - I have a '93 w124. It will no longer blow hot air no matter what climate control setting I put it on (auto / ec, etc). The a/c works fine when I want it to and blows ice cold.

I've found a lot of posts around blower motors and a/c's not working, but not where the heating function is the only thing that doesn't work.

I'm thinking it is potentially a bad climate control unit, but I'm definitely not an expert! I'm somewhat handy so if there's any diagnosis I can do with instructions, I'm all for it.

Thanks

If it seems as if your A/C is stuck "ON" all the time I would think that the control unit is the culprit. If, however, it is just blowing ambient air from outside when you have the climate control set to blow hot air then I have a feeling the mono valve could be faulty and thus is not circulating warm coolant into the heater core.

Correction: heater valve

W124 Mono Valve replacment

It's definitely blowing ambient air outside air at whatever fanspeed I set it to so sounds like the culprit would be the heater valve. Thanks I will give that a shot!

__________________
1993 300CE