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Discussion Starter · #1 ·
I just replaced the (very dirty and clogged) orifice tube, receiver drier, and high side port on my 99 Astro, and charged it up with 3 lb of R134a.

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At first I was perfectly happy, the AC was blowing ice cold as I had the van idling out by the garage. Then I went out for a drive.

It seems that as soon as I get higher in RPM (manifold vacuum drops), I get straight heat out of the front vents. Rear AC still seems to blow cold. I saw the diagram online, which seems to show that the temperature blend door is controlled by an electric actuator, not a vacuum one.

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Is the diagram I saw incorrect? Or does anyone have any other suggestions on what could be causing my ice cold air to turn burning hot as soon as I rev up the engine? Could my heater control actuator be somehow plumbed in wrong on the vacuum side? Or maybe I'm missing a one way valve somewhere.

The air returns to ice cold as soon as RPMs drop, so I'm fairly certain that this is vacuum related. I appreciate any advice.

Thanks
Max
 

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Discussion Starter · #2 ·
Update: I took a longer drive to bring my girlfriend some coffee at work (read; further diagnose) and found that the van does not pump out heat if I set the dial to defrost. Furthermore, if I first set it to defrost THEN back to normal AC, it will not pump out heat. The problem only occurs when I go from "off" to "AC" or "Max AC".
 

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Common Sense + Critical Thinking
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Diagram looks correct, yes temperature door is electronically controlled.

So let me make sure that I understand this correctly.

A/C is functioning perfectly fine at low RPM, when you rev the engine the air is coming out of the same vents(doesn't change vents) but now it's HOT. As soon as you let off the gas, it returns to being ice cold again. While all of this is happening the rear A/C is constantly blowing cold air just fine. In addition to that, defrost is not getting HOT.


The most common issues are vacuum related, make sure that the lines under the hood are properly installed and not leaking(check the elbows carefully sometimes they crack and only show if you bend them slightly), as well as the check tee and the storage ball. When in defrost the A/C is running AND air is directed through the heater core, that could be a door issue, or even a water control valve issue if the heater core isn't getting hot.

I have had a sticky blend door actuator before where I had to flip back and forth before getting it to move. It actually cleared up after some time but it doesn't seem like that is your issue or at least it's not the only issue.
 
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