Armstrong gas furnace won't kick off

QUESTION:

I have a Armstrong Air Ultra V - Tech 80 furnace with a Honeywell Smartvalve II SV9520H which doesn't start. Here are the details about the problem:
1. When the thermostat is on the OFF position, the led indicating the status is showing the normal function "heartbeat"
2. Turn the heat on the thermostat (80 F) and set the thermostat to AUTO - nothing happens, the furnace won't kick off.
3. Set the thermostat switch to ON - the blower kicks off but the gas won't light. After about 20-30 seconds, the status led starts flashing 3 times which means: "Presure switch open. Should be closed".
NOTE: The gas is on and the furnace turned on from the main switch.
Any idea of what might be wrong with the furnace and how can I solve the problem?

ANSWER:

Is the switch on the gas valve turned on? I have seen weird lockout codes caused by this...
Turning the tstat to on, should only turn on the fan, not the heat. You may have a low voltage wiring problem.
There's a good possibility you have a bad smart valve though, they are crap.
BTW when you say the blower starts, is that the fan that moves air thru the house, or the fan that blows the smoke outside? If in fact the ventor motor is starting, the fan that blows smoke outside, I agree with the other suggestion, find the blockage in your flue pipe.


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