Would replacing the switch require evacuation of the system?

 

Randy. Everything I've read says there is a schrader valve where the pressure switch screws in at. So no, you shouldn't need to evacuate the system.
However. There's always a chance that the valve could stick open when you remove the old switch. If that happens you may lose the refrigerant.

Haven't read the service manual on this but the recommended procedure may be to remove some of the refrigerant to reduce the static pressure before you do this repair.

 

If you read the Owner Manual you would find that the AC always runs when in recirc or defrost mode, the light on the button will not illuminate.

The compressor should never cycle on/off. Either the pressure switch has a problem or the pressure is a problem. You can get a cheap AC gauge set at Harbor Freight and return it when done. Yes, there is a Schrader valve under the switch.

 

ok, I will obtain a pressure guage. The compressor is cycling on and off in short bursts constantly. I'm leaning toward the pressure switch from what you guys are saying. But I really don't know air conditioning systems at all. Regarding your signature line, do you use standard or metric hammers?

 

Have the system drained and replace the high side valve, as they always fail. If the compressor was cycling the switch is work as designed, let it alone.
Adding freon is a guessing game, overfilling will produce results as bad as underfilling. Tolerance is only an ounce or so!
Vacuum the system for 30 minutes and see if the needle holds at about -29. If it does, add 14.4 ounces of R-134 that doesn't have sealer or leak detector. Add 1 ounce of PAG 46 oil.
Be sure to have a small scale to weigh the can, as filling has to be precise.
The vents should put out around 42 degree air. Now you're good for 10 years.
I did this with my '07 HHR and the vehicle gets cold fast!

I have a vacuum pump attached after replacing the high-side Schrader valve