I have an 85 300D and would like to know what years the parts from other 300D's would interchange. I also would like to know what year I would need to get the manuel heat controls. My heat and air does not work, and I would like to switch to manuel controls.

For most average parts, a 82-85 300D is exactly the same. There are some differences in an 85 like the rear differential.

It would be a lot of work to switch to manual controls. I've read of one or two people doing it on here. It will be much, much easier to fix what is wrong with yours.
First, does your push button unit work at all? IE-Does the blower come on and push air around? Do the flaps change when you push the defrost from another button? Start there.

Your air not working is usually because something has failed in that system like the compressor vs the electronics/vacuum that control it.

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2009 ML320 Bluetec
1985 300CD
1981 300TD

Past Mercedes
1979 300TD
1982 300TD
2000 E320 4Matic Wagon
1998 E430
1984 300SD
1980 300SD

You're not going to find any 300D's with manual heat controls unless they are a Euro vehicle..........very rare.

The best choice is to fix the automatic controls. They work very well when they are functioning properly.

I have a '77 240D, US model "parts car" with manual AC controls.....that should work, and I am saving them in case I have a problem with my controls in the future......

SB

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Diesels:
'85 300D, "Max, Blue Benz", 155K, 27.0 MPG
'84 190D 2.2, "Eva, Brown Benz", 142K, 40.2 MPG
'77 240D (parts car)
'67 Eicher ES 202 Tractor "Otto" (2cyl, Air Cooled, 30HP)
Gassers:
'94 Ford F-150, "Henry", 170K (300 Six) 17.5 MPG
'85 190E 2.3, 148K....Parts Car
'58 Dodge W300M Powerwagon (Flat Fenders) Less than 10 MPG

Right now the known problems are bad compressor, which for now I'll ignore it the belt is off, and unplugged electrically. The heat control valve is not working,athough power is going to it, and the center vents do not come on. fan works on all speeds, and the rest of the flaps do work. My concern is long term, if this system is problematic why fix it, change now for better reliability. However if it can be fixed and be reliable then keeping it would be less work.

The system isn't "problematic". It's over 20 years old and nobody put a penny into it for that entire time period.

Replace the failed components and you'll get 5-10 years of trouble free service from it.

The effort to locate and install a manual system is about 10X the effort to maintain the current system.

The center vents do not work unless the system is attempting to Cool.

My 300D AC compressor is in need of repair...but the vents all do cycle as they should as the system moves from Heat to Cool and vice versa......

The Monovalve.....there is a rebuild kit available.....but....in my case, once I got it to move, it has been operational ever since......

Also, according to MB......you should run the system in economy rather than off......

SB

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Diesels:
'85 300D, "Max, Blue Benz", 155K, 27.0 MPG
'84 190D 2.2, "Eva, Brown Benz", 142K, 40.2 MPG
'77 240D (parts car)
'67 Eicher ES 202 Tractor "Otto" (2cyl, Air Cooled, 30HP)
Gassers:
'94 Ford F-150, "Henry", 170K (300 Six) 17.5 MPG
'85 190E 2.3, 148K....Parts Car
'58 Dodge W300M Powerwagon (Flat Fenders) Less than 10 MPG

Thanks for the advice. I'll take a look at the monovalve, and repair- replace it, then go from there. As long as I can get the original system working good, I'll stick with it.

Now you're thinkin'...........

The fact that your fan and most of the vents work is at least half the battle. The center vents work only when the system is cooling. They will open on a hot day even if you are in "EC" mode -- the a/c compressor does not have to be working -- it just has to be cooler outside than in the car's sun-baked interior. Fixing the monovalve is easy and you can live without the a/c compressor if you have to.

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

It's the early "evil" climate control you have to worry about.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine