2002 Taurus A/C issue

Hello Group,

I have search and could not find a solution to my problem. While checking out my mother's car, I discovered that the A/C compressor and Fan will not turn on when the dash controls are on A/C or A/C Max. Where should I look first to diagnose this problem.

Abe

See how much charge is in the system. If it is low on r134 than neither will turn on.