The a/c clutch will cycle when its in the max, a/c, floor/defrost and defrost positions. It may have low refrigerant level or a bad low pressure side switch or hi pressure side switch switch which protect the compressor. Have someone check the refrigerant level first.
'00 XLT 3.0 Exted cab
Mods: Roush hood & cai, ASP pwr pulley, hot wtr bypass, 180 therm, e-fan, Gibson exh., 4.10 l/s, FabTech lift, kyb's, bii sway bar. 31x10.50 Yokahama ATs, Panther rims, light bar, SS grille, 03 stang buckets, explorer console, hurst shifter