Problems with fan clutch and AC blowing hot air

My 2001 GMC ac blows hot air from time to time approx 3 yrs. I've not had it diagnosed but I turn off the engine and restart and then it resets itself.

Hello! A fan clutch typically refers to the mechanism responsible for turning the engine's fan, which, when engaged, pulls air through the radiator and keeps the engine at the correct operating temp(which is why it is loud at times). When a fan clutch fails, it is usually disengaged and will not properly cool the engine, even though the fan looks like it is spinning. This increases the danger of overheating the engine, which can lead to severe damage. It is not unsafe, per se, but greatly increases the danger of a breakdown from overheating the engine. It is unlikely the AC blowing hot air is related to the engine's fan clutch.