[W126 Coupe] Suspect pressure switch issue on the receiver dryer

[Dick Spellman]

Hi Jonathan:

Got everything buttoned up, vac'd things down, started the load with 
R-134 and stopped when high side static pressure hit 100lbs at 80F.  
Compressor would not kick in!  I suspect it's the new pressure sensor on 
the new r/d since that is the only wiring I removed and then 
re-attached.  The other sensor with leads is for the fan on/off based on 
temp if that's correct.  But, I don't use this switch where I have the 
relay to kick the fan when the compressor clutch engages as per Stu 
Ritter.  Been working fine that way for years.

Questions.
Anyway to test that pressure switch?
Is it normally open (N.O.) or normally closed (N.C.) when it reads 
pressures as OKAY?
Is this switch reading both high and low or just low pressure when it 
actuates?

With this bit of info I can either remove a lead opening a closed 
circuit or jumper the two leads to close an open circuit.  Then I will 
proceed with the fill procedure once again.  Kinda need to know how the 
switch performs before I load more refrigerant in the system.

Any info will be of help.

Thanks,

Dick