I am hoping someone can help we have a Tempstar NUGK059 Gas Furnace - the pilot does not light and the furnace blower runs but only blows cold air. We thought it was the old thermostat - replaced the thermostat - double checked wiring. Same problem. Help it is -7 here in the Midwest. After reading some of the other posts, it sounds like maybe the limit switch(s) - looked in the furnace - but have no wiring diagram to go by to check limit switch and could not find owner manual or diagram. Any help would greatly be appreciated.

Thank you

If you had an idea of how old your furnace is it would help. Also it would help to know how the furnace acts as you turn the thermostat up for it to heat.

Check on the back of the blower access door for a diagram.

Thanks so much...
Age - over 15 years old
Checked the back of the blower door - foam insulation but no diagram

letmetellu: There is no change when I turn the thermostat up... same

Model number not listed recheck for correct number so I can find out what type of system you have.

Does the ignitor glow?

Thanks hvac1000

Unit is Tempstar Gas Furnace

Model number is nugk059mf06
867.769415
S/N L903455241

No glow - does not ignite only sound is blower - and blows cold air

First thing to do is look for the circuit board. The board will flash a series of blinks on a small lite on the board.

Have the thermostat set to heat then go to the furnace and turn off the power. Wait a minute or two and turn the power back on. The system should start to work but when it fails to fire it will set the blink code. We need to code to narrow down the possible cause.

I have searched and have found no wiring diagram for your unit. I suggest looking around since all furnace manufactures attach a wiring diagram somewhere on the unit. Contained on that diagram will be the blink code. Post the blink number and what the code says is wrong. I will keep searching for a diagram but hold little hope of finding one.