12.10.2009

How I Cleared our Furnance Air Intake Pipe and Saved a $200 After Hours Service Call

On Tuesday I left work early for two reasons. One, to stop by and finally get my truck from the mechanic's where it's been for 3 weeks and two; because we were expecting a blizzard.

By Tuesday night I was home bound with teenagers and by Wednesday morning we had a 4 foot tall drift completely obliterating our driveway and surprise... no heat.

Around 11:00 I had realized the house felt a few degree's colder than I thought it should. A quick check of the thermostat showed me it was indeed, about 3 degrees cooler than it was 30 minutes before and there was no heat. Our furnace had stopped working.

Not knowing anything about heating and cooling systems, I spent the next 3 1/2 hours trying to think of what it could be and even looked online to gain insight. Unfortunately the internet was no help at all, which leads me to this post.

All furnaces are different, are installed different and have different set ups. Obviously don't base your entire DIY on this post, but I do hope to help by pointing out some things to look for if your furnace stops. I managed to fix it myself and saved us a $200 after hours service call. I hope you can save a little cash too!

Look for the obvious;

  • Check the thermostat to make sure it's set correctly. It should be set on 'heat' and the fan should be set to 'auto'. Turning the fan to 'on' will make it run continuously but it won't have warm air coming out of the vents.
  • Check that the temperature of the air is not already warmer than the setting for the furnace. If your room air is 69 degrees and you have the thermostat set at 68, it will not be running until the air temperature drops to below 68.
  • If you don't know if your fan motor is working, turn the fan setting to 'on' and listen. If it's running, you know your motor is working fine.
  • The most important, number one thing you can now do to check why your furnace stopped is to bundle up warmly and go outside to check the pvc pipes that stick out from the outside wall of your house and make sure the intake and exhaust pipes are not blocked or clogged. More often than not this will be your problem. If you clear them and it still won't work, then take a look at your furnace.

I have a Lennox with a small port hole shape in the front that you can look through to see two green lights inside. These lights blink certain ways to troubleshoot the furnace. The cheat sheet is a sticker on the front of the furnace to tell you what the flashing, blinking or solid lights mean. Check yours and act accordingly.

Try turning the system completely off and on again. When it comes on, listen for the fan to start followed by the 'woosh' sound of the flames catching to heat the air. If you hear the fan, then the click and the woosh but then it goes out within a few seconds... you have an obstruction blocking the air intake.

To check this, remove the front panel from the furnace.

If you are like me and know nothing about furnace systems, this will be intimidating at first. Lots of wires, tubes, and scary looking things! These are the fan motor, the gas line, the on/off switch for the gas, the reset button, etc. At this point you may see a second panel - on mine it was silver and it was bolted in place with four bolts, covering the flames. It also had a port hole window to peek through to check for fire.

If your furnace is not working, you will not see the blue flame. It will be dead and cold.

Remove the safety panel. Now, with the panel off and the air flow open, try to start your furnace again by turning it up a degree or two so it kicks on.

Mine took about a minute or two and I didn't think it would work; be patient. First the fan motor ran for about a minute followed by a red glow starting in the right hand side of the upper burners and then woosh! The blue flames were burning. At this point, with the panel in place, the air was cut off and it went out.

This told me (and the service technician I was on the phone with) that since it was running just fine with the panel off, that I still had an air obstruction somewhere.

At this point I was so happy to have heat I just let it run wide open, knowing it was in the furnace room, behind a closed door, with no pets or children anywhere near and with no way of getting into the room. I was happy to have heat!

The most obvious obstruction was the snow - which I had cleared away from the pipe but it was clear I still had some obstructing it. The intake pipe is a curve, so I had to brainstorm something I could use to stick into the curved PVC pipe to clear any snow that may have gotten sucked up into it before I had cleared the area around it.

The Christmas tree! You can use what you wish, but I used the bottom branch of our fake Christmas tree. It was long, thin and bendable yet sturdy so while I waited inside the house by the thermostat, I sent my 17 year old son outside to see if he could clear the pipe.

Bingo!

Sure enough, he said there was just a bit of snow at the 'elbow' of the bend. Once it was cleared the air could enter freely and as I replaced the panel on the furnace and saw the flames still strong and steady, I knew it was fixed.

Cost? ZERO! Love that.
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