Heater works once, then stops

[ckpark]

Hi, first time poster here.

I installed a new thermostat because my gas fired heater would come on, light itself, and heat the house for a few minutes but then shuts down. However, the new programmable thermostat hasn't changed the behavior. I can turn the thermostat off and on again and the furnace will light and run as before, but never reaches the setpoint temperature. Any ideas? Thanks.

-C

[Joel]

check your fan motor is running correctly sounds like the furnace is going off on limmit and when you interupt the power source it is resetting the limit switch and runs till it goes off on limit again ,also a dirty filter will throw the limit