lennox g26 prim/sec limit switch says open after shutoff restart works ok rest of day?

Question

has a 63K8901 control board bad?

recycling ac power causes unit to work normally, as does doing nothing at all. It comes on by itself after about 20 min. past the thermostat call for heat. The house gets colder than it should before the unit restarts. I'm guessing its the control board itself but then again I'm just guessing.

Answer 1

More info would be nice. Do you turn off the power to the unit (115v) to reset it? If so, the primary limit that senses temperature at the exchanger is tripping. Most of the time this happens because of low air flow due to dirty filters or rooms that have had the vent closed because they get too hot. Secondary switches reset automatically without having to interup power. E-mail me if you need professional guidance.

Answer 2

From my experience, intermitent problems have usualy been with a control board. You may not be able to parts from Lennox on your own. Best bet would be to call a Lennox service company to come out and verify the problem so you don't throw money away getting the wrong parts. There are other parts of the system that could be inputing to the problem. Play it safe, it is winter time.

Answer 3

Before spending money, check to see if your filter is clogged. This would cause the bonnet temperature to go too high and cause a shutdown.

Answer 4

check the flame sensor use some Emery cloth or the like to scrub the tarnish off and re-install