I have an older Trane gas garage heater. It hangs in ceiling and has a blower fan. I have just installed this in a new home and the pilot lights OK. But I do not have a thermostat wiring diagram fot the 24v transformer hook up to the gas valve/thermostat. There are two 24v ac wires running from the transformer to the gas valve - not labeled or color coded. There are 3 terminals on the transformer and 3 terminals on the gas valve, two being used to deliver 24v to gas valve. Without a thermostat hookup ( jumper circuit) the gas valve does not function. What should I do?

The third terminal on the transformer could be an unused center tap. I don't understand what the third wire on the gas valve is. If you connect the 2 wires from the transformer to the 2 terminals on the gas valve, it should open. If it doesn't, one of them is bad.