Blend door
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1st Gear
Joined: May 2023
Posts: 1
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Blend door
Could someone tell me what acuates the air conditioning / heat door. My 1980 C3 has a very cold evaporator but the air from the vents is not cold. It seems as of the door for the cold air is not opening. Any help would be greatly appreciated 👍
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Joined: Nov 2006
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From: Sunshine Coast, Queensland, Australia
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Cruise-In VIII Veteran
The cable that attaches to the hot /cold lever. And when the door is swung all the way closed hits the vacuum switch that sends vacuum to shut off the hot water to the heater core.
perhaps you haven't had a look? Perhaps you don't own genuine G.M service manual?
perhaps you haven't had a look? Perhaps you don't own genuine G.M service manual?
Instructor
Joined: May 2021
Posts: 225
Likes: 73
From: Missouri
4-vettes is right on. The cold/hot slider controls a cable that adjusts the hot/cold blend door. In addition, the plastic plunger valve that sits on the top of the heater box under the dash shuts off the hot water valve. That plunger can get out of adjustment and the actual heater control valve in the engine bay rusts and sticks open as well. Many folks remove it and put in a manual ball valve but a properly working new one works just as well.
