[JRTJH]

Possibly a thermostat problem. I'd first check it by turning the thermostat up to about 85F or so, turn it to heat and see what happens. If it works, it's the thermostat. If it doesn't, I'd suspect an electrical connection problem or the control board. Start by checking ALL wiring going to the furnace for any loose or corroded connections, make sure the fuse socke.ts are clean and secure (no loose fitting fuse blades) and that there is 13.6VDC at the control board. If that's good, then I'd replace the control board.

My recommendation is a Dinosaur Electronics board rather than an OEM board. They seem to be more reliable, better built and usually less expensive.