A/C compressor will not engage. Where is the relay? Fuse is good. on 1993 Chevrolet Suburban 2500

With the A/C selected on HVAC panel. The HVAC blows warm air. The A/C compressor clutch does not engage. Has R-12. What else can I do asa backyard mechanic?

Asked by for the 1993 Chevrolet Suburban 2500
ck your a/c relay under hood and then ck pressures on freon charge.with a/c turned on ck pwr to cutch assm if no pwr there jump a/c cycling switch at pigtail. if a/c comes on possibly low freon or bad switch