Gas and Oil Home Heating Furnaces - won't shut off

my furnance can't seem to heat my house to 72 it hasn't shut off in two days

Start by checking for a plugged furnace filter, covered over return air grill or war or warm air vent that are closed.

i cleaned air filter opened all dampers and left the cover off the cold air return on furnace so it could get for air if needed. i had a guy come out last week and changed the transformer because i shorted it out hooking up a humidifier that already had a transformer built in could something else have gotten messed up thanks for your help it really means

i cleaned air filter opened all dampers and left the cover off the cold air return on furnace so it could get for air if needed. i had a guy come out last week and changed the transformer because i shorted it out hooking up a humidifier that already had a transformer built in could something else have gotten messed up. thanks for your help it really means

Too bad --- you're not lucky today!


Well then, you need to post the make and model of the furnace which you get from the rating plate of the furnace in the burner compartment.

Post the make and model of the ignition module if there is one, and any flashing diagnostic codes it may be signaling. If they are listed, post the problem listed for that diagnostic code, often found on the furnace somewhere in the burner or on the fan compartment door.

Observe what is happening with the fan and burners until you can describe and post any patterns that exist.

I would guess that the fan is running constantly buy the burners cycle on and off every 3-5 minutes or so, but other patterns are possible.

If you can locate and identify the main limit switch, measure the 24 volts to that and see if it shuts off on one side of the limit when the burner is off.

its a true temp or a cleveland dornback 120000 btu tag to worn out for year,it doesn't seem to have an ignition mod. also noticed that there isn't alot of heat comeing out of stack not like other houses on my street. also noticed that burners will not lite with fan running so they to are always on also on plate cdl-120 tc2-71-436

Does the furnace have a pilot light to light the burners? If not, what?

If the burners are operating continuously, you probably have a gas pressure problem that is reducing the heat input to the furnace, just as you suggest.

Do you have other gas applaince? How do the burners operate on those?

Do you have natural gas?

Check to see that the electric gas valve is fully turned to the on position, ditto for the furnace shutoff valve. Check the valve at the gas meter which should be pointing in line with the pipe, indicating that it's fully on.


Is there any indication of the burner surging or getting bigger or smaller in size?

Thanks! I think that was the problem. Seems like we are getting heat now. Really appreciate all your help. The valve in the furnace was not fully on. It is a good night to have heat.