a/c pressure cycling switch settings for R12 (Page 1/1) freek JUN 26, 04:25 PM does anybody know the a/c pressure cycling settings for the HR6 compressor, 87 V6, based on R12 AC coolant? RWDPLZ JUN 26, 06:06 PM R-12 refrigerant, switch should turn on at 25psi on the low side. It's adjusted on the switch itself in the front compartment on the accumulator, you have to unplug it to access the screw that adjusts the pressure.