This all started about a week ago. One night we woke up to a very cold house. The furnace hadn't kicked on at all during the night. It's an Armstrong ultra sx80. It has the automatic ignition. When I went to check on it, I took off the panels and vaccuumed it out and noticed that when I ran the vaccuum brush over the circuit board, I heard a click and the furnace turned on. But that didn't fix my problem. It rarely turns on by itself now, I am constantly having to take the front off to run a brush over the circuit board. We have a thermostat that is maybe a year old so I know it isn't that. If anybody has any suggestions, please help!

It could also be a loose connection. Is the circuit board flashing a code?