I have a Mueller Climatrol Model 137-115. I came home at lunch the fan was blowing.
When I set the thermostat to 70 the burners kick on and heat up and it heats the house. When the house gets to desired temperature the fans stays on, burners go off. I've changed thermostat, same thing happened, so I don't think it's the switch. Anyone have any ideas.
Many Thanks

Have same problem.
It's the relay or switch on furnace.
I remove front panel, find rocker switch at lower left, switch it off and on a few times, then back to auto.
This always resolves problem for a few months.
Whenever I feel cool air from room vents, I repeat.
Now it's 2016 and I want a manual for the furnace (I am renter).

MUELLER CLIMATROL
MODEL 137-115

NEED MANUAL.