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Thanks, I knew somebody would have some info on this subject

Originally Posted by gmac

Yes, here it is again, "what does 3 flash error mean"? I of course know what it typically means, but when all normal checks have been done, and show no problem, what is a common problem with these furnaces, that causes this to happen? Is there a common problem with the control boards?(i suspect this).I have seen times when the thermostat causes this.

80% Two stage:

3 flashes - Low-fire pressure, rollout, or aux limit switch open.

80% and 90% units:

3 flashes - pressure switch open with inducer ON.

Note:
Some of the pre Oct. 2011 90% furnaces had pressure switch issues. A bulletin was put out about it, but it did not to say to go out and replace these switches.

It stated that a review of warranty claims on these switches showed most of them had signs of being exposed to moisture, and this was probably due to improper furnace installation, or an incorrectly mounted condensate trap.

They did say that as of about Oct. 2011, a new manufactured switch was being introduced that had Gold alloy contacts to prevents oxidation and wiping action which would reduce “won’t close” failures.

Armstrong Furnace 3flash problem

Yes, here it is again, "what does 3 flash error mean"?I of course know what it typically means, but when all normal checks have been done, and show no problem, what is a common problem with these furnaces, that causes this to happen?Is there a common problem with the control boards?(i suspect this).I have seen times when the thermostat causes this.I know it sounds illogical, but I've removed the stat from the circuit, and jumped r to w , then it ran perfect-I've seen this at least twice-wtf?