[boomgagem]

Hey everyone, maybe someone can help me figure out what to look for. I have an outdoor Heat/AC unit, it is one big unit. The heater uses gas. The A/C works fine with no problems at all. But the heater will not come on. I can turn on the heat, and turn the Fan on, and it will blow, but cool air. I have followed the instructions as far as turning the ignition switch on. When I turn the heater on with the thermostat inside, I can hear a little motor running outside, but nothing happens, and after about 2-3 minutes, it shuts off. I'm not sure what to check for, anyone else have this problem before?

[SublimeMasterJW]

The draft motor comes on and causes a vacuum in a proving switch which powers up the brain. If all rollout safety switchs are on then the gas valve and igniter come on. The flame switch then sends back the news to the brain Houston we have ignition. The heat then builds in the furnace till around 110f and that makes a klixon throw the fan on and nice warm air comes out the heater. If you are getting cold air then something is amiss. Must be a faulty relay on the board. The fan is not supposed to blow till heat is present in the furnace.