My air conditioner won't get cold.it just blows hot air

Electrical or mechanical failure?? That is first to be determined.

This could be many things. If the ac system has never been serviced before it could simply need a recharge. Its is common and normal for an ac system to lose freon over many years and if your car has not been serviced since it was new then this could very well be the issue. A simple test of the system would find out what is wrong.