The compressor iced up? Not sure how that is possible. The receiver/dryer (the can) can get iced up, which can be normal during use. If the evaporator is icing up restricting air flow, it might be low on charge or the low pressure switch isn't kicking in to prevent this.
BTW, A/C automatically comes on with defrost mode. If you have the manual HVAC system, even if you have the knob just one click towards defrost, it kicks on the compressor. If you want to stop this, pull out the compressor relay.