300D 1977: SERVO UNIT

Hi,
There is a coolant leak from this "SERVO UNI" also known as "part 0008300684" or "ACC Servo" or "Heater Control Valve". I couldn't find much
information about this mysterious part but got idea that it responsible in some way for vacuum system and heating and ventilation. Price for this part is SO MUCH and my car is so old that I think I can survive without heating and ventilation. But now sometimes I have a problem with engine overheating because I think leak through this servo unit. My idea is: can I just block coolant circulation through this part by jamming its pipes? I think it will stop leak but will it create any other problem? My main concern of this solution are: will it create engine overheating? will defrosting of windshield work?
Thank you for any advice
Alex
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The '77 - '80 climate control has two problematic parts: the "amplifier" (logic board located behind the glove box) and the "servo" which controls the heat, vacuum ducts and fan speed. Both are available as rebuilt units.
These servos are available rebuilt for about $400 plus the old unit. This lousy thing is so intregal to the car's climate control that nothing will happen without it. You can bypass it by routing the coolant line past it but then, unless you also install a valve you'll have full heat all the time. Or, if you plug the heater lines, no heat or defrost.
I've replaced several of these after their plastic bases cracked and leaked. Some of the rebuilt units substitute an aluminum base to prevent such leaks.
The amplifier gets cracks in its board and the climate control suddenly becomes erratic and unresponsive to the controls. Rebuilds cost about $100 the last time I checked.
These parts can be bought from on-line parts suppliers.
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Where are you finding the servos for around $400? everywhere I've looked they are $700-$900 rebuilt.

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Try Geroge Murphy at Performance Analysis in Oak Ridge, TN. he rebuilds them with an Aluminum housing.
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http://germanstar.net/123h.htm
Ron http://germanstar.net
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The '77 - '80 climate control has two problematic parts: the "amplifier"
(logic board located behind the glove box) and the "servo" which controls the heat, vacuum ducts and fan speed. Both are available as rebuilt units.
These servos are available rebuilt for about $400 plus the old unit. This lousy thing is so intregal to the car's climate control that nothing will happen without it. You can bypass it by routing the coolant
line past it but then, unless you also install a valve you'll have full heat all the time. Or, if you plug the heater lines, no heat or defrost.
I've replaced several of these after their plastic bases cracked and leaked. Some of the rebuilt units substitute an aluminum base to prevent
such leaks.
The amplifier gets cracks in its board and the climate control suddenly becomes erratic and unresponsive to the controls. Rebuilds cost about $100 the last time I checked.
These parts can be bought from on-line parts suppliers.
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If you choose to have the coolant by-pass the servo then you must also "jump" the cold engine lock out which is a bi-metallic vacuum switch on the very bottom of the servo. It is ON only after coolant warms it, otherwise it's OFF. By-passing the servo would leave this switch cold and the climate control system would always be OFF. "Jumping" the vacuum switch is done by coupling the two vacuum lines.
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Thank you very much! You were so helpful!
Alex

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