AC high pressure cut out switch needed or not?

[hatzie]

Alabama qualifies as a HOT climate New England does not. R134 runs higher pressures than hydrocarbon blend or R12 refrigerants. The R134 system on my 2000 GMC C2500 T400 chassis has a high pressure cutoff switch. If GM decided it was necessary on the factory R134 system it should be installed on a retrofit.

On my 2000 GMC 2500 T400 chassis the switch on the accumulator is the LPCO and the switch on the compressor is the HPCO. I mimicked that setup on the '98 6.5L with its' H series compressor that I installed in my '76. I put in a parallel flow condenser, variable orifice valve and late 80's accumulator/evaporator. I have yet to see high pressure cutout... but #1 I was extremely careful about charging using gauges and thermometers not assuming using pounds of refrigerant. #2 I was in Cincinnati and am now in Northern New England so summer isn't as rough as the Deep South. On the 76 My high side pressure is reasonable at 90°F ambient temp and My vent temps are 40-45°F.

Make sure the HPCO is on the high side and LPCO is on the low side.