I have a Lennox XP-19 HP and last night, I noticed that it would cycle on for about 10-15 minutes and then off for 10-15 min, but it was running only on the 2nd stage. I know it was on 2nd stage because the furnace LED indicator showed it was on 2nd stage. The temperature outside was 38 and the stat was set to hold at 69. I would expect it run on 1st stage either continuously or at least start on 1st stage and run there for a while. Another piece of info is that a week ago when it was a bit warmer, it was running on 1st stage mostly. Why would it now cycle on and off on 2nd stage only?
Here is the exact equipment I have:
Furance - Lennox G60UHV60D-135
HP - Lennox XP19-060
Stat - Honeywell IAQ