I have a natural gas furnace made by Heil. The model number is NTC6075FBA1. The serial number is L984120332.

A few times over the past year, I've noticed the furnace blowing cold air constantly. I "solved" the problem by shutting off the furnace via the circuit breaker, and then turning it on again a few hours later. Unfortunately, this method doesn't work anymore.

The furnace constantly blows cold air, and the heat never comes on. The thermostat was an old-fashioned dial-type model. I replaced it with a modern electronic thermostat made by Honeywell. Didn't make any difference. Changing the temperature-setting on the thermostat has no effect.

When I take off the upper panel of the furnace while it's blowing, it looks to me like there is a pilot light burning. But I don't know anything about furnaces, so I don't know what else to look for.

The house is getting cold, and I can't really afford to get a repairman right now. Thanks in advance for considering this question.

--
Alex C. in Rochester, NY

You say this furnace has a piolit light? Does it vent with metal or plastic pipe?

We went through this a few winters, now have a new high efficiency gas furnace, half the size of the old one which was about 40 years old. At times the reset button worked for us, at times too, it was the air intake from the outside which was clogged with snow and ice. I know this may not be the case now, this early in the season, but just putting it out there. What it came down to, the old one was just not functioning properly anymore and repairs were getting too much.

Tick

you say this furnace has a piolit light? does it vent with metal or plastic pipe?

It vents with a metal pipe. Thanks.

Look for a fan contol in the upper cabnit of your furnace.

http://www.cozyparts.com/Lennox-Parts/images/15P38sm.jpg

look for a fan contol in the upper cabnit of your furnace.

http://www.cozyparts.com/Lennox-Parts/images/15P38sm.jpg

Josh, I don't really see anything that looks like that part. Would it be helpful if I posted a photograph?

Yea a photo always helps

yea a photo always helps

Here are some photographs of the furnace:

http://www.smugmug.com/gallery/10164685_8CRgP#699436685_4Y34H

Follow the red wires to the small switches, there should be a red button between the wires push on them to make sure the limits are not triped.

follow the red wires to the small switches, there should be a red button between the wires push on them to make sure the limits are not triped.

Josh, I pushed on the red buttons, but they didn't seem to move at all. I turned on the furnace (at the level of the circuit breaker), but it's still just blowing cold air.

Well the last thing to check would be the limit control might be stuck. Pic number 4 with the 2 red wires going to it just to the left of the green paper tab. Peck it gently with a screwdriver.

well the last thing to check would be the limit control might be stuck. pic number 4 with the 2 red wires going to it just to the left of the green paper tab. peck it gently with a screwdriver.

I opened the panel and moved the wires around, I re-seated some of the connections, and I tapped on a bunch of stuff. The furnace works now, so thanks for the advice. However, I'm still nervous about the possibility that the same problem will recur in the middle of February during sub-zero temperatures. I wish I new what the problem was. I may have to call a repairman anyway.

Thanks for the useful advice.

If you have a pilot light there will be a gas off/on control between the gas pipe and the furnace which will have a pilot light position for relighting the furnace. If you lit the furnace pilot and did not advance the control to the full on position after doing that the gas won't come on for heat but just supply enough to keep the pilot running. This is for safety while lighting so you don't get enough gas for a big whoomp until the pilot is lit and running long enough to heat the thermo couple switch

I opened the panel and moved the wires around, I re-seated some of the connections, and I tapped on a bunch of stuff. The furnace works now.
Did you observe any oxidation of the electrical connections? If so, your action may have "scrubbed" and restored the connection(s).

I realize that this is an old thread, but we were having the same issue with our furnace. Googled the model number and came across this thread. Tried everything I could think of, and everything else I had seen elsewhere online. Tried what Joshdta suggested and it worked.

Just wanted to post this in case others were still searching for solutions and ran across this thread.

I realize that this is an old thread, but we were having the same issue with our furnace. Googled the model number and came across this thread. Tried everything I could think of, and everything else I had seen elsewhere online. Tried what Joshdta suggested and it worked.

Just wanted to go ahead and post this in case others were still searching for solutions and ran across this thread.

Thanks, Chad, your input is appreciated. Some people gravitate to the old threads and I hope they get some good out of them.

Tick

I wanted to provide an update. It turned out that one of our cats had peed into the furnace (from above), and the cat pee had rotted-out the electronics in the furnace. Apparently, cat urine very corrosive -- or so I was told by the repairman. So we ended up getting a new furnace.