1 blinking light, runs for a few hours or a few days and all of a sudden it will cycle 3 times and shut down, sometimes it will light for a second and blower comes on right away. And then cycle 3 times and shut down

Check or clean flame sensor rod or switch

The problem is the stack over temp sensor located...

The problem is the stack over temp sensor located on the front of the fume exaust fan. The stack over temp sensor is prematurely tripping thus dropping the 24v to gas valve. The unit tries to...

The problem is the stack over temp sensor located on the front of the fume exaust fan. The stack over temp sensor is prematurely tripping thus dropping the 24v to gas valve. The unit tries to re-light 3 times and after 3 failed attemps the circuit board goes into fault mode with the flash code of 1. This is the code for ignition falure. When this occurs the power to the furnace must be cycled to return to service. You can test if the stack sensor is bad by bypassing it. If the furnace runs normally then you know it's the stack over temp sensor.

WOW,, HVACTECH has his crystal ball tuned up and working in super fine shape

Id say. But is seems to have a glitch. Can only put out so much info at a time. Lol.

My crystal ball isn't working so good, but, model number of furnace may help. I suspect flame senser, but there are many things that could be causing the problem. Ill wait for more info from Pete, and see if one of us can't help him out.