Furnace Out

After a long first week back at work after the holidays, I woke up Saturday morning feeling cold. It wasn’t just me–the whole house was cold. The furnace was out. Winter this year has been uncommonly warm, but Saturday was a cold day.

I checked the thermostat, and it appeared to be functioning, but the vents weren’t blowing at all. Something was off–the fan wasn’t blowing but the burners were all on (there are supposed to be safety features to prevent that). I turned the thermostat off and on again, hoping it would reset something, but no luck. I watched several YouTube videos about furnace troubleshooting, and it seems that the most common issue for a fan not starting is a bad capacitor.

For context, this is a 26 year old furnace in a 52 year old hours. We knew when we bought the house that the furnace was going to need replacing at some point, but we were hoping for a planned replacement, not an emergency replacement in January. I picked up a space heater from Becca’s work and our friends dropped off another two space heaters. I started a fire in the fireplace and all the kids bundled up in blankets.

It took a while, but I found the capacitor and safely removed it (370 volts is a lot of volts). I texted a friend who owns an HVAC business, and he said Grover’s carries replacement capacitors. I drove over there, and they had the right part in stock after waiting for my number to be called (they had to get it from the back). I got it installed, and… nothing.

(Here’s a picture of me still optimistic before installing the capacitor)

I used my trusty multimeter to see if the motor was getting power, but the leads weren’t accessible in the cramped space, so I measured the control board outputs. The board wasn’t sending power to the motor at all. After confirming my suspicions with my friend, I found a replacement control board with next day delivery and took a break. I’m not sure how it took most of the day, but it did.

(Here’s the old control board with my awesome magnetic work lights)

Sunday morning, the new control board arrived. After church and feeding the kids, I got to work installing it. It was a bit fiddly, but I got it done without too much trouble. I powered it on, and… the fan started blowing! Success!

(Here’s the burned old control board)

The old board left a burn mark on the furnace casing, so something failed pretty spectacularly. I’m just glad it didn’t catch the house on fire. The furnace is now working fine, and the house is warm. I took today off work to recover from the weekend’s excitement and get some rest. Hopefully, the rest of winter will be uneventful!

(Here’s the new control board installed and working)