A/C on a 93

I purchase this Van (93, 3.0L) in 1999. The air conditioning never worked on it but I never tried to fix it. This weekend I quickly tried to look at it but I'm not familiar with the A/C system.

When I press the A/C button, it truns blue but nothing happens..?
Is the engine RPM supposed to change? Is something supposed to make noise? I'm probably out of freon (I think it uses R13 something). I noticed that they sell these freon replacement kit at the local store, you simply screw the can in one of the ports and it refill the system.

Any help to start the troubleshooting would be nice.

Seb

The 1999 uses R12 and will have to be changed to R134 which is readily available at most autopart stores but R12 is not. The reason nothing is happening is because there is a low pressure cutoff switch and when the freon gets too low the AC system will not come on. You need to locate the leak first. I suggest you go to an AC shop as they should be able to locate it for you rather quickly and will recharge it at a reasonable cost with R134 as it will require complete evacuation of the system to work. Most diy'ers don't have the proper equipment.
As far as the engine RPM increasing yes it should and the fans should come on.