when i try to screw new switch on i hear a click and air seems to be escaping from switch. When i put the old one back on it goes on properly what am i doing wrong any on to help me i have a 1999 chevy blazer

 

First off, are you sure that the switches are identical?

If they are identical (including the o-ring), does refrigerant continue to come out if you fully tighten the low pressure switch?

 

yes as well as air pressure

 

Could you phrase that a little more descriptively...? What do you mean by "air pressure"?

 

well when i am screwing the switch on i can hear and feel air escaping from where the switch is been screwed on

it feels as though air pressure is been released

 

So...

 

yes refridgerant continue to come out when i tighten the new switch. When i put the old switch back in it goes on without any problem but it does not cycle the a/c compressor clutch

 

Something is pushing on the check valve in the connection and not allowing the sensor to be properly tightened down to where the o-ring would seal the connection up. It sounds like something is different between the two sensors...

 

well first of all let me thank you SWARTLKK for hanging in there with me. What i am doing right now is take it back to advance auto and let the salesman check again to make sure he gave me the right part. I will also take the old one also.THanks again and when i get the new part i will hit the forum and let you know the progress of this repair.