Hi Folks,

I have a 1993 Bonneville SLE naturally aspirated, 128k on the clock. Decided to put some work into my a/c system as it was only running about 75 degree vent temperature on a 85 degree day (ambient temp). Had my shop evac my system, took car home and hooked up my gauge set and vacuum pump. Pulled vacuum for about two hours. Left manifold gauges on after pull down; did not indicate any leaks. Recharged to spec (r12 to r134 conversion done by a shop in 1995) so I was mindful that the system takes less r134. Regardless, gauges indicated fill was within spec.

After refill, ac clutch ran continuously. Took car for a ride; vent temp went down to 60 degrees which is not great. This morning was cool (about 55 degrees) and I noticed that the ac clutch cycled on and off. It has the HR6 compressor. Should it cycle when it is cool because the system pressure is lower in cooler weather or does this indicate that perhaps my charge is still low and I should add more r134? I did not change the orifice tube because I cannot find where it is and forum answers are all over the board.

Your suggestions and help is greatly appreciated!

It is typical for the clutch to cycle at lower temperatures. You would be best served by throwing the full set of gauges on the A/c just to make sure pressures are behaving properly. I never have truly been happy with the conversion cooling results, and the A/c pulls a very noticeable amount of power too.

I have been contemplating converting to R-152a, as others have mentioned its properties are closer to R12 than R-134a.