My AC Light stays on and don't heat my car

You should still have heat even if your ac is "on." All that means is the ac compressor is running. Every time your defrost is on the ac is on too because its removing the humidity from the air. You have a different problem and it could be as easly as low coolant, a bad thermostat, or a blend door in the dash that isn't working. Either way it all needs to be properly diagnosed by a mechanic at this point. Alex