what you are doing is bypassing the pressure switch. Do you have voltage on the other blue wire of the pressure switch? Did you try to bridge those two blue wires ? You didnt mention anything about a relay. Do you have pressure in the ac system? When you're checking wires, are you checking for continuity,voltage?

__________________
'85 300D Cal 280,000 miles
'14 GLK 350 60000 miles

I bridged the 2 wires on LP switch and nothing, and no continuity on the volt meter
I have continuity on the low pressure switch. A circuit tester also gets nothingfrom either low pressere wires. With the bluegreen(BG) wire removed i bridged to the + battery terminal to it and the compressor engages. replace it and nothing.
if i remove the red/blue(RB) wireand bridge to the + bat terminal nothing. with the RB wire removed and I bridge the +term to the low pressure switch. the compressor engages. Ithem reatached the RB wire to the low PS and bridged that connection to the + terminal and it engages the compressor. when it's bridged at either of the successfull attemts the on off switch on the console does not turn it on or off. i tried 2 different switches that had continuity and the same results, no control.
QUESTION NOW IS: If i run a wire to the interior from the + battery terminal to a toggle switch then back to the LP switch connection where the RB wire is attached (instead of directly to the +bat term) this should allow me to turn the compressor on or off. BIG QUESTION: will this harm the system in any way. I do appreciate your response . I'm desperate. RAY M

I just put 3 cans of freon in prior to this. changed dryer, exp valve,compressor and blew out lines with flush good.It runs real cool when it engages

MY123ca I removed my glove box to see where i could run the wires. towards th upper left there was a Red blue wire that had disconnected. It wasn't visable when i removed the undercarrage below the glove box. I must have bumped it off when reaching underneath to reconnect the air ductI removed for working space. I had to reconnect it by feel not sight because i couldn't fit in there to see. I want to thank you verry much for your help.