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Old 05-24-2023, 03:18 PM
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north north is offline
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I agree that a factory AC on a 69 GTO should be icy cold if you want. If you are not getting air that cold (as opposed to zero cooling) there are a few possible causes.

First as mentioned is the refrigerant, when GM switched the R134 in 94 they increased the size of the evaporators and condensers about 30% to compensate for the weaker thermal capacity relative to R12. So if you are running R134 it should still be fine for all but the worst days but definitely not up to factory spec.

Second is insufficient refrigerant level.

Third is a malfunction of the hot water cut off valve. This valve is vacuum controlled and it functions when the temperature slider is in full cold position to the far left. It cuts hot engine coolant flow to the heater core when activated

Forth is malfunction or bad adjustment of the flapper doors which are cable controlled by the temperature slider

Fifth is decades of filth blocking the evaporator in the dash, this limits both airflow and heat transfer resulting in lower vent flow and warmer temperatures.

Lastly the evaporator in front of the radiator may also be blocked by dirt and grime reducing heat transfer.

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