AC/Heater Controls and Air Flow Problem
- Thread starter 84Elky
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veltboy314 – Great Pics. Thanks. I’m learning more about this AC/Heater stuff than I ever wanted to know. The pics, and the attached diagram from a 1986 G-Body Shop manual, help my understanding of some of the doors. Pic #4 confirms that when the AC/Heat door is pushed all the way toward the firewall (as shown in the pic), it closes off heat coming from the Heater Core, and provides AC cooled air or outside temp air. In Pic #2, it’s just the opposite. This just further proves why it is not necessary to have a heater control valve. Yea, the heater core is always hot, but if air does not flow through the heater core, no hot air can be generated.
Pic #5 appears to be the Air Inlet Door (white plastic). Question - is it open or closed in the position shown? It looks like it is closed (as if in recirculate position to prevent outside air from entering the cabin).
So here’s what I’ve learned. The hot air from the heater ducts is only felt when the windows are open. What’s apparently happening is that my hood is not totally sealed at the back and engine heat is escaping there and being “sucked” into the Cabin Air Intake (under the windshield on the passenger side).
When the windows are open, air is not being prevented from entering the cabin as it is when the windows are closed (higher pressure in the cabin with windows closed). So, you get increased air flow into the cabin with windows open, and this increased air flow sucks more air out of the back of the hood which is causing the heat.
When the windows are closed, only a small amount of outside air comes through the heater vents, and its volume is not speed dependent. It never changes, and the air temp is the same as outside. Here, because there is a small velocity of air being allowed into the cabin, hot air is not being “sucked” out of the back of the hood into the Cabin Air Intake.
If my hood was totally sealed at the back, I’m confident that the hot air with the windows open would disappear and be the same temp as the outside air. I may stuff a towel along the back of the hood to prove that theory when I get some time.
Pic #5 appears to be the Air Inlet Door (white plastic). Question - is it open or closed in the position shown? It looks like it is closed (as if in recirculate position to prevent outside air from entering the cabin).
So here’s what I’ve learned. The hot air from the heater ducts is only felt when the windows are open. What’s apparently happening is that my hood is not totally sealed at the back and engine heat is escaping there and being “sucked” into the Cabin Air Intake (under the windshield on the passenger side).
When the windows are open, air is not being prevented from entering the cabin as it is when the windows are closed (higher pressure in the cabin with windows closed). So, you get increased air flow into the cabin with windows open, and this increased air flow sucks more air out of the back of the hood which is causing the heat.
When the windows are closed, only a small amount of outside air comes through the heater vents, and its volume is not speed dependent. It never changes, and the air temp is the same as outside. Here, because there is a small velocity of air being allowed into the cabin, hot air is not being “sucked” out of the back of the hood into the Cabin Air Intake.
If my hood was totally sealed at the back, I’m confident that the hot air with the windows open would disappear and be the same temp as the outside air. I may stuff a towel along the back of the hood to prove that theory when I get some time.
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