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Discussion Starter #1
I have a 79 450 SL and it is missing a part and I was wondering if anyone might be able to tell me what it is. In the engine compartment by the firewall in front of the passenger compartment there is a bracket and there are two (at least) vacuum hoses that are not connected and there are two electrical connectors that have about six wires on each one. The a/c does not work and the blower fan only comes on with the defroster.
This car has California emmisions. I am suspicious that it is a temperature control unit but I can't find the connectors on any schematic that I've seen so far. There is also an aux heater pump that is in series with the heater coil that works when you apply 12 V DC externally but the plug never is energized by the car so I think it is tied in somehow.
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Discussion Starter #2
picture of connectors to missing part

Here is a photo of the connectors to the part I am missing. Can anyone identify what the part is?
I appreciate any help.
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I believe you are missing the climate control servo. This is an expensive part for what i...

I believe you are missing the climate control servo. This is an expensive part for what it does. So, it wouldn't surprise me that someone bypassed it when it broke which is every 50K miles or 3 years to prevent antifreeze from leaking.

It's about $800 new or you can get a rebuilt from George Murphy. I forgot the name of his company. He sells a replacement which has an die cast case instead of the plastic one which cracks.

CB
 

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Thank you china blue!

China blue,
Many thanks for the info. I do remember seeing a post about the die cast servo units some time ago. I had no idea that the part I was missing was the servo so your info is very helpful.
Tom
 

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Question about A/C Servo and amplifiers

I take it the two plugs in the photo in my earlier post above connect each to an amplifier (is that right? I can't tell because the amplifiers are missing). From a parts picture it looks like there are vacuum connections to the a/c servo as well as heater hose connections. Does anyone have a digital picture of this hook up or a drawing so I can see how things are connected. I have the Haynes and the Chilton manuals for this car and neither one shows the electrical or heater connections for these devices. Is there a better manual that has this information? Is there a specific Mercedes manual that covers the control circuit for the climate control devices so I can troubleshoot the rest of the circuit?
Any help is appreciated. Here is a picture of my baby.
 

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