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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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