I tried looking for the answer but had no luck. I own a 1991 300E w124 like the title of the post says I got hot air coming out of the A/C vents. The fans still work I mean I can turn on the A/C but no cold air comes out just hot air. I never turn the A/C on for the same reason that only hot air comes out. But now I've noticed that even when my A/C is off I got hot air coming out. It bothers me a lot because after riding in the car for a while you can notice it & I end up having to roll down my windows.

Is there any quick fix for this?

-Thanks in advanced.

You have coolant running into your heater core when its not supposed to be. Try bypassing the heater core. my heater core has a crack and was leaking coolant into my car so I bypassed it and in doing so I have no heat (I live in 100°+ desert anyways), but I also don't have the problem of getting heat from my vents when my ac is on (my problem was a broken heater valve).

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1990 190E 3.0L