A/C Pressure Switch Question

If the low pressure switch at the reciever dryer is disconnected, will the compressor then engage with a low pressure in the system? While doing an A/C recharge, in order to get the compressor to turn initially to take the charge, rather than a 12 volt jumper to the A/C (which in my Monidial is difficult to access) to briefly engage the clutch for this purspose, I thought this approach would be simpler?

 

1988 Mondial Cab 3.2.

Thanks for the quick response. Should be much easier to jump the switch as you ntoed than fiddle around at the far back of the engine bay area with a 12 volt source while the manifolfd and charge equipment is all set up in the same area...perhaps a small initial charge into the evacuated system with the engine off will be sufficient to allow the clutch to engage when the engine is turned on for the remaining charge, but I want to be ready for all of the possible surprises...

When calibrating the charge volume, I see from various sources the 134a charge weight should be anywhere from 80% to 95% of the charge wieght of r12. Big range, the Sanden manual suggests 95%, but I don't want to overcharge?

 

Thanks for all the comments. I did jump the pressure switch, and this worked, and engaged the compressor as hoped. I had replaced the compressor, and condensor, etc., and therefore needed a full charge. After evacuating (using a homemade pump from an old fridge compressor), did the full charge based on the charge weight as set out in the manual, 1.2kg of freon, scaled back at 90% for the 134a, and further calculations to accomodate the oil volume and residual oil in the system (some examples set out in the Sanden compressor manual which was available on-line) A/c now works perfectly, and the low pressure reads about 30lb. at a fairly cool 60-65F ambient temperature. Will recheck at a higher ambient temperature to make sure the pressures remain within range.

I know a/c systms require expertise, but this was a straighforward component renewal matter, all other components in good shape, system previously flushed at a shop, and lots of research on my part. Long live the handyman...