You say heater not working , if the blower works but no heat comes thru then check coolant level pronto. But if you mean the blower wont blow then first check your fuse panel for blown fuse related to the heating system circuit in question. Then check all ground connections related to the circuit in question. Under the hood you can find the heater blower motor connections (the squirl cage mounted on the firewall is the blower motor), check them first easy to get to. clean connections. you can bypass the heating control switches and do a direct 12v jumper to the blower motor, also run a ground jumper to the ground connection on the blower motor as well, if your 12v jumper makes the blower come on then you know the proplem is not the blower motor itself. This leaves the wiring or the switches or any other ground connections in the blower circuit to be the cause.