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82 300SD fiwer, 83 300SD parts car, for now...
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128 Posts
Discussion Starter #1
On my 1982 300sd I can't get the vent to move to the heat position, only defrost, a bit of searching hasn't turned up any obvious culprits and I don't want to jump in blind, can anyone give me some pointers here? Is this vacuum operated?
 

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2012 CL550 4MATIC Coupe
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9,992 Posts
Defrost is the default for total vacuum failure to the HVAC - because the car is still safe to drive that way.
+1 Read my repair and DIY Thread.
 

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1985 300sd
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45 Posts
welcome to my world, i just had the same problem with my '85sd. there are various things that can cause this, most likely a vacuum leak. from one of your vacuum actuators, switchover valves, or vacuum lines.mine was a bad actuator for the center vents leaking. i disconnected it plugged the line and all the other functions worked properly. you'll need a vacuum pump to check them with. i'll check back with you later gotta go to work!
 

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82 300SD fiwer, 83 300SD parts car, for now...
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128 Posts
Discussion Starter #6
Thanks for the replies, can anyone tell me where the vacuum lines come out under the hood? I changed the engine and think I got everything back where it belongs, but that may be a good start.
 

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1983 300SD
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396 Posts
On my car the defrost works but not enough heat coming out through the vents, could it be the same problem? I have changed the climate control twice, but didn't make any difference.Where do I start?
 
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