furnace has mind of its own

[gator4sale]

hi, have a coleman furnace, durning the day keeps the right tem. at night will not go above 64' it will run for about 10 min shut down and restart in a few minutes
i change the thermastat 4 times, each does the same thing,
al

[lonestarheir]

I know this probably sounds like a stupid question, but have you changed anything (thermostat, etc...) like maybe put in a programmable in where a mechanical thermostat was?

When you say each time it does the same thing - does the thermostat go back to a setting of 64 each time you raise it? or what do you mean

You very well could just have a bad thermostat. Most of the time, if a system is working correctly (which you say it does during the day) at any time, things like what you describe turns out to be a control issue, either user or damaged mechanics.

[HayZee518]

OK, you say you changed the "stat." 4X you say! Did you adjust the heat anticipator on the "stat?" This is the little movable copper arrow on a scale to match your burner amp rating. The "stat" either mechanical or electronic needs this anticipator adjusted to compensate for under and overshoot of the room temperature when the stat reaches the set point. Operates on 24 volt and minimal current. The stat is the brains of a burner.