I have a coleman furnace. The burner will turn on but shuts off after about one minute before reaching desired temp. Any idea why?

Hi, daddyj!

How old is the furnace as well as the thermostat, please? Its possible that the thermostat might be defective.

Hopefully, others will also be along to address your question.

Thanks!

Thermostat is new.Furnace approx 20 years old.

Does the Blower come on?

Does the Blower come on?
The blower comes on but then something is making gas valve shut off. Blower continues running for a couple of minutes then shuts off. I only seem to have this problem when out side temp. gets above 25 degrees. Colder than that it seems to work fine. Any ideas?

Is the Air filter clean? Does the gas burner come back on after the blower shuts down?

Is the Air filter clean? Does the gas burner come back on after the blower shuts down?

Air filter is new gas comes back on if I turn furnace off for a few seconds

Have you check gas press

If it has a new thermostat and it is digital, make sure it is set to oil /Gas on the back side of the thermostat. Some Digital Thermostats bought at places like Lowe's or Home depot require you to select oil/Gas or Electric on the back. This has to do with the heat anticipator if it is not set correctly it can shut the cycle down prematurely. Also if you have to turn the unit off then on to get it to run, that says that you are resetting a control. If it is a standing pilot system and the flame keeps going out and gas pressure is fine, then I would say Thermocouple is suspect. If it hasn't been serviced in awhile, the flues could be blocked up causing the system to go off on Spill switch or roll out switch, with the unit being 20 years old those switches may not be manual resetting but automatic switches that reset with disconnecting power then returning power. Sounds like you need a Contractor to look at it. Gas is no joke and not for the novice handy man (not doubting your talents) but if your not in the business it's best to have trained personnel look it over.