System: Bryant 333BAV 80 plus furnace, 10 yrs old, with Honeywell Chromotherm III thermostat. No problems with either in the past. Minnesota. January.

Upon waking up this morning, found the house was 58 degrees, with set point at 68. Checking the thermostat, found it was showing "AC" (power outage to furnace?). Breaker to furnace was not tripped. Checking the furnace, it appeared to have no power: no sounds, and not even the red LED in front was lit. I turned off, and then (right away) back on the power switch on side of furnace. No changes. Connected right below that switch on the side of furnace is a 2-outlet box. I went and got a trouble-light and plugged into one of the two outlets. Immediately upon plugging it in, the condensate pump (which was plugged into the other of the two outlets) started to run, for about half a minute. Also at that same moment, the furnace turned on: red LED lit up (solid ON, no "trouble code") in front, and fan and burner sounds started. Furnace has now heated the house up, apparently running just fine.

I have a second (separate) furnace in the house, so can afford to wait and watch a bit.

What could have caused the furnace *power* to shut off, and why did my simple actions this morning "fix" the issue, and how can I (or, can I?) troubleshoot it further?

Thanks.

Check for a loose wiring connection or bad ground in the electrical wiring. I would start by looking in the 2 outlet box.