I've got a bad switch, middle one of three on the bottom of the condensor, and I'm wondering if the system needs to be evacuated before changing. Someone told me there was a valve that would seal it from leaking when removed.

I don't want to dump my R134 trying.
Doe's anyone know if these switches go often. I think this is the second one for this car in two years. It causes the cooling fan to come on and stay.

Thanks for any feedback.