last night after the 15 minutes runs, then stop with 6 flash code, Im not able to bring it back after long cooling. So put the furnace to OFF before bed.
This morning I put the thermostat to COOL position, FAN to auto.
Turn on the furnace, back to the thermostat, turn the FAN to ON, blower starts after couple of seconds. Once again the blower will starts at COOL position. Later flip the swithc to HEAT, couple more seconds later gas starts, warm air came out in minutes.
It ran for more than 2 hours non-stop by now.
This furnace has no AC, AC was added later years. It might explain why there is only one speed.
Any suggestion or comments to above problems?
Thanks.