Hey all the heater in my 2000 300M just recently got stuck at max heat and in defrost mode. The digtal display lights show the mode changing but it only blows hot air on the windshield. The display lights also show the temp changing up/down when I adjust it but the temp stays and full heat . The fans speeds works fine and the A/C is not on while the defrost is blowing the heat if that makes any difference. My 103 mile drive to work every morning with freezing feet/hot face is getting old quick ! Any ideas where to start looking? Thanks for your help

Have you tried this?

Doing that three button test would occasionally fix the A/C in my 2002 Concorde Limited.
Do that and find out what code it gives you. I have a list of them at home.

Problems with the auto A/C is one of the reasons I sold my Concorde. That stuff was extremely expensive and has been discontinued.

Thanks for the help guys. I just tried the code reading trick and it says code #24. Any ideas?

24 is the mode door actuator failure.

It means you're stuck with air blasting out of the current vents.

The ATC and manual AC systems had different actuators. If I recall correctly, replacing them requires a dashectomy.

The actuator I needed was discontinued.

I noticed after I did the code reading trick that the heat can now be adjusted up/down. That's an improvement but the vents are still stuck at defrost mode. Does this mean anything? Am I still looking at a dashectomy?

I just did this on my 2000 300M. I had code #24 Mode door actuator.
Bought the part at the dealer.
I installed mine through the radio opening. Didnt have to take the dash all apart. Google it and you will find pictures info and a youtube video on how to fix it.