can i replace the ac temp switch without evacuating system
 

on my 88 124 can i replace ac temp switch,on the reciever drier, with out removing freon. the car still has the green switch and want to put the red one on. this is to turn on aux. fan on at a lower temp? while doing a search a few weeks ago i read something about a 123 that said this could be done. sounded kind of odd as i would think the freon is right behind the switch. why else would there be a green o-ring on the switch.
do these switches leak internally? or does just the o-ring leak?
i ask because i have a used one.
the squeak you hear is me thinking of spending money.
its kind of a dumb question,but hate to mess with the r-12 when it still works.
thanks
rich

Aux fan switch on your drier to replace it you have to remove freon first on 123 model aux fan switch is switch on by temp not pressure of the freon. I will go for a new switch not a use one (R12 $$$)

MB STARS, thank you very much. that explains the green o-ring on the switch

rich