My garage heater was working early this winter. I turned the thermostat to 0, but when I went to restart heater nothing happens, can you help me with this problem?

Check for a fuse either in-line or on the circuit board. There should be 24 volts going to the thermostat. If not, you have either a bad transformer or a bad thermostat wire. Jump out the terminals that the thermostat wires are connected to. This should force the unit to fire. If not, bad circuit board.