Does ac low pressure switch replacement require evacuation?

[zombezoo]

My switch seems to be bad, does anyone know if the removal of the low pressure switch releases the freon in the system? Not sure if I need to have it evacuated first.

 

[Ronnman]

If the switch is the type that screws into the upper part of the filter drier, then yes, you need to evacuate the system. On the original systems, there was no Schrader valve underneath, since loss of refrigerant was comman and the cost cheap. If in another location, I’m not sure?
Ron

 

[zombezoo]

Thanks Ron. My system switch is on the dryer as your photo shows. Turns out my system was already empty but you are right, there is no valve in the block to keep the system charged when the switch is changed.

 

[Darter6]

Some GM cars/trucks has the Schrader valve and were removable, Mopar not sure.
My 93 Chevy truck took about a minute to change and A/C restored.