Hi all,
A while of searching revealed nothing too clear to me so I will start a thread and seek some advice. My beautiful 300D has the infamous climate system everyone hates and that never works. Fine, it defaults to only the defrost working, which here in the NW has worked fine for me for the past 5 years. But just this week, my defrost setting has stopped blowing hot air. The fan still works the same, but only cold air comes out.

Now I'm aware of basic heater functioning, so while on the road I immediately became fixated on my temperature gauge fearing I had somehow drained all my coolant on the road, but my temperature sat at the usual temp.

So something is preventing the hot coolant from getting to the radiator for the heater. My search revealed something about a monovalve, but it's not clear that my 79 has one. Any advice on the simple cheap way to get this working again? When I am rich someday I would like to spend the 1,000 on the solid state system that will run the whole HVAC as it should work, but for now, just getting defrost to work would be great! Thanks for any help.

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Where there's a will there's a way
1978 300D