Just last night I awoke from a nap with my wife to find our house to be about five degrees colder than the thermostat was set for. I could hear the furnace continuing to kick on, but no heat was coming from any of our vents. I'm not much of a handyman, and certainly am not an expert in HVAC.
I called my uncle who happens to work in the HVAC profession. He gave me advice on how to diagnose the issues with my furnace and how to go about resolving them. A day later, I was able to fix my furnace myself with his simple instructions. So, what would cause a furnace not to kick on?
I opened the back of my furnace and saw that the small red bulb was blinking 3 times before stopping and repeating again. On the furnace door, you'll see a sheet of paper that has various codes and what they mean.
3 blinks means there is an issue with the pressure sensor switch. This can occur for various reasons, whether that's your exhaust vent is blocked by a birds nest, a strong wind gusted in and messed up the sensors, or the sensor needs to be replaced.
If it's simply a sensor issue, then you can flip the breaker attached to your furnace and wait about 30 seconds. When you flip it back on everything should be right as rain! The same goes for your blocked vent. If you find the blockage, you just need to clear it and your furnace should right itself shortly after.
Another way to check your switch is to take the hose from your pressure switch and gently, as if you were going to whistle, suck on the end. You should hear a small click sound and another click when you take your mouth from the hose. If you don't hear that sound, you need to replace your pressure sensor. If the hose appears to be brittle, cracked, or has any cuts or tears, then you will need to replace your hose as well.
Replacing a pressure sensor switch is so simple that my uncle who works in HVAC simply told me to attach the new piece the same way the old piece was attached and that it should work:
The initial glow of the furnace.
You will need to make sure whatever sensor you buy is one that fits your model of furnace. To check this, there should be a model number posted among many other things on the inside or outside of your furnace. Mine was inside the furnace, just to the left. You can call your local supplier, or even purchase your sensor on Amazon or eBay. Once you get the correct part, the replacement is as simple as 1, 2, 3.
The model number can be identified in the upper right-hand corner of the information sheet.
In conclusion, even a person who is just starting to learn about home improvement can fix a pressure sensor on their furnace. Because of my uncle's information, I was able to avoid a service fee to a local repairman that would have probably been far more expensive than what the 5 minutes of work would have been worth.
© 2019 Jesse Unk