After furnace runs for a while and cycles off furnace will not fire back up unless I power off then turn back on

The starter board controls everything. Pull it out, find a replacemeny on the internet. Make sure the power is off.

The fan is activated by a time delay switch on the control board. But before you spend big money on a new board check these things. 1. Is the blower wheel clean. 2. Is the filter clean if you have one. 3. If it has a/c on this unit and has been run without a filter the evap coil may be packed with dirt causing and overheat situation. 4. Do you have any collapsed ducting or room vents shut off. Is it cycling on the limit switch. (you can test this with a thermometer, first measure the air temp entering the furnace, usually at the return. Second measure the air temp leaving the furnace. as close to furnace as possible. The difference of these two numbers is temperature rise. Check the label on the furnace and it will give you the rated temperature rise for that furnace. Take these measurements after the furnace has been running 10 minutes to get an accurate reading. If it exceeds the maximum rated rise the heater has an air restriction or blockage.) You can also jump the two wires going to the limit and run it through a cycle to see if it still short cycles afterward. If the problem goes away then you have an overheating issue. If it continues its probably the board.

The reset button near the ignitor is a high temperature limit safety switch. When the furnace gets too hot and the manual reset limit switch is tripped, it most likely goes into a 'safe' mode where the gas control is locked out electronically and the blower is made to run continuously to rid the heat exchanger of the excessive heat. This will continue until the reset is pushed and the power is cycled off. It will remain an endless cycle unless the reason for the overtemperature condition is not corrected.

Your furnace 'temperature rise' is getting too high due to a lack of air across the heat exchanger for whatever reason. Some of those reasons could be a restricted air filter or a blower motor that's cycling improperly on its internal winding thermostat. You could also have a dirty air conditioner 'A' coil (evaporator) on top of the furnace restricting the air flow. Nevertheless, you are going to have to have it serviced by a reputable service company's technician to correct what's wrong.

How old is your furnace? Does it have a circuit board that controls everything, or are there separate controls for each function?

1) Shut power to furnace off, take panels off furnace.
2) Bottom part of furnace find the thermostat wires and make sure they are not touching each other where they connect control boards. You Should see Terminals R,G,W and Y.

3)This is a typical wiring if done by technician.
R=Power-should be red wire
W=Heat-should be white wire
G=Fan-should be green wire
Y=Cool-should be yellow or blue wire.

4) Disconnect the G terminal which is the fan leg and move it out of the way. Turn power on and turn thermostat up. The fan should not turn on until after the burners turn on. The fan should cycle off about 60secs. after the burner turns off.

5) If all of this happens make sure the wires at the thermostat are wired the same at the furnace Red to R and Green to G.
The color of wires you have may be different. But if the same colors are connected at the same terminals at the furnace and the thermostat, that is all that matters.

6) If you recently changed the thermostat, make sure the Rd or R terminal wire is not touching the G terminal wire at the thermostat.

It sounds like your flue work in your main problem get this fixed first then see how it runs , pipes should run all the way out of the chimney .

it sounds like the low temp limit switch, the one that cools the furnace down with the burner off and the thermostat open, when it cools to a point the fan stops, the other switch in burner area turns burner off/on, hope this helps

1) Turn the fan to on and if it runs you know that you have line
voltage to furnace and 24volts to the thermostat.

2) You could turn the furnace off remove the doors and get to the
control board. If you can find the Thermostat wires on the board
mark and remove them. If you have a typical Furnace and you
have some electrical background put a jumper wire between
terminals R and W,put the doors back on-there is a door switch
that if the panel is not put back on-it will not run. Turn your power
back on.

3) The Blower motor may come on, the induced draft blower should
come on, the glow coil should glow, the gas valve open and the
burners should come on and the unit should run.

4) If all of this happens, then you have a thermostat problem or you
have bad thermostat wires.

5) If nothing happens then you don`t have power to the furnace or the
little fuse that protects the transformer is blown.

Good Luck

The Miller furnaces sometimes will do that. Does this have surface ignitor that glows. Kill power to furnace for few seconds and turn it back on. See if it will go thri the cycle and see if coil glows. If not chances are coil is bad. Need to call service tech for free estimate. Rus

Probably need to replace the limit. Pull the wires off of the limit and set your meter to ohms. If it beeps while holding one test lead on each of the connectors on the limit itself then it should be good. If no beep it may be stuck, still too hot, or bad part. Try to give it a whack with something solid like the end of a screwdriver sometimes this will release a stuck limit. If you get it to fire up and heat again make sure your blower comes on and your filter is cleaned. You need to check the temperature rise on your furnace afterwards. Limits dont trip for no reason usually.