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A/C Blowing Out Defroster Only


Mr. Anderson

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I'm finishing the last few things on the interior of the 91, so I thought it would be appropriate to ask this now:

 

Since I have bought the car, the air has only come through the defroster vent. It will also come through the floor vents if the ECC is in BI-LEV or HEATER. There is no blockage to my knowledge in the system, and the A/C is a r-134 system that does blow cold air. The compressor and clutch engage as they should, so I'm betting that the system is functioning properly.

 

Am I looking at a vacuum line needing fixed or is this related to the arm that runs to the top of the HVAC programmer?

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Guest HuevosRanchero

on mine the vacuum check valve at the middle  of the firewall had neatly split in half at the seam. Impossible to see or even hear until I touched it. 

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This morning I found a badly disintegrated vacuum line going to the vacuum reserve tank. It literally fell apart in my hands. Hopefully this solves the issue because I did the tests in the A/C diagnostic section of the FSM and it appears that everything is working as it should be, at least according to the computer and the programmer.

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Guest PontiacDude210

On a car that age, you may want to inspect all your vacuum lines. I had several that broke but were sticky enough to collapse and not leak. Weird to try to track down.

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I replaced a vacuum line to the reserve tank and still have no luck with the A/C. The FSM says that if A/C blows out defrost but not vents then to check upper mode valve. Where exactly is this valve? If I could guess it would be all the way behind the dash where I can't get to it.

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