how do you manually switch from heat to a/c if the motor is out?

ok so in the winter i couldnt get the heat to work so i took it to the shop. they informed me the motor that turns it from a/c to heat was out. and seeing how i couldnt afford the part at that time they "manually" switched it. Now that its out i need to know how to turn it back to a/c and where this switch is?? please help its hot