Fan cycles on and off between heating cycles.
The Temp in house is 67 and Heat setting is set to 67 the reading on the thermostat never changes, but the heat kicks on and off. Between heat cycles the fan cycles without the burner being on. I have a Honeywell Programmable Digital Thermostat set on 67 Hold 2-3 years old. I have two one upstairs and one down. I tried swapping the two, no change. My heating unit is a Janitrol about 19 years old 1986 model. I have had five Technicians to the house, the first one replaced the Fan limit control. The settings on the new one are 150, 110, and 50. All the other techs said it was out of adjustment.

I observed the cycle pattern last night
3:32 am Burner turns on
3:33 Burner still on, Fan turns on
3:36 Burner turns off, Fan still on
3:36 Fan turns off (within the same minute)
3:39 Burner NOT on, but Fan turns on
3:40 Fan turns off

3:44 Burner turns on
3:45 Burner still on, Fan Turns on
3:47 Burner turns off Fan still on
3:48 Fan turns off
3:51 Burner Not on, but Fan turns on
3:52 Fan turn off

3:58 the above pattern starts again

Any suggestions?