It all started on Tuesday morning when my wife heard a strange and loud noise from our furnace. She took a picture of the exhaust vent and texted me, asking if the steam coming from the vent was normal:
The steam was normal, I said, but the noise concerned me. That night, when I got home from work, it was still happening. It was a clanking, rattling noise that was so loud that we could easily hear it when sitting upstairs in our living room watching TV. I went down to the basement and took this video up close:
I read a few articles online and one troubleshooter suggested changing the filter. Our wasn't that old – I'd changed it a month or two ago – but I tried just in case. I also powered down the furnace using the emergency electric cut-off switch, waited a few minutes, and then started it back up. The noise was gone. Problem solved. Or so we thought…
On Saturday morning at 1:00 a.m., my wife woke up to feed our month-old baby and found that cold air was blowing out of the vents and that the temperature in the house had fallen to 65°. By 6:00 a.m. the temp had fallen to 63° and she woke me up to tell me what was going on.
Downstairs, I found that the fan was still blowing, but that the blue flames inside the furance itself were missing:
I called my dad and asked for advice. He suggested looking for an indicator light, seeing if there was a pattern and, if there was, looking in the manual to see what it meant. I found the light on the bottom panel of the furnace:
Turns out, the red furnace indicator light uses Morse code to spell out a problem number, which you can then look up in your furnace's owner manual. Our light was blinking 6 times:
I found the owner's manual for our furnace, and it said that 6 Flashes meant that the rollout limit circuit was open.
I found a few articles online suggesting tips for how to remedy that. One suggestion was that I check the incoming air vents for any obstructions. That was my next step, but it didn't lead to anything; the pipe was clean.
At that point, I realized that I needed to call an HVAC expert, but it was the Saturday after Christmas, so everyone was running on emergency rates and had little-to-no availability. After checking several reviews and calling around a bit, I finally got ahold of a guy who not only guaranteed that he could make it out that day, but also offered a bit of troubleshooting over the phone. When I told him that the the rollout limit circuit was open, he suggested that I reset it.
After a bit of research, I discovered that the rollout limit circuit is a safety mechanism that helps to shut off the furnace when things aren't right. Although this can be very helpful, it can also be the source of a false positive – the rollout limit circuit itself can go bad. So, a good troubleshooting step was to reset it and see what happened.
There were two rollout limit circuits that I could find in our furnace:
I pressed the button on both to reset them and found that the one on the left was, in fact, open. It clicked when I pressed it.
"Sweet! Problem solved," I thought… I turned the furnace back on to see if that had done the trick. Nothing happened.
After almost a minute with nothing happening, I decided that I should probably cut the power and wait for the HVAC guy to get there since I didn't really know what I was doing.
When he arrived, the furnace started right up for him with no problem. D'oh! I was thinking that I simply hadn't waited long enough after reseting the rollout limit circuit. But, before I could spend too much time feeling like an idiot, the furnace acted up – badly – and I learned that I had made the right call by being cautious.
The furnace's main blue flames were pouring back out towards us; a situation that seemed very dangerous. He switched the furnace off right away then explained to me that the primary heat exchanger was busted.
He wanted to double check a couple things so we waited a couple minutes and then started it up again. This time, it was working perfectly. Weird. He turned it off and on again, and the same thing happened; it was working just fine.
But, on the third try, after removing the bottom panel again, we saw the problem again clearly:
Because it was a holiday weekend, the soonest we could even hope to get parts was Monday. So, we were facing at least two days with no heat, maybe more. What a fun holiday surprise…
Just to make sure we understood the severity of the situation, the HVAC guy made me sign this note saying that I was aware that using the furnace before it was fixed would cause "loss of life and property." Gulp.
The new heat exchanger wasn't available locally, but they were able to overnight it and it arrived Tuesday afternoon. The HVAC company sent out a guy Wednesday morning to install it. A couple hours and $675 later (the warranty covered the part itself, but not the labor), our house finally had heat again!
This post was published on December 27th, 2014 by Robert James Reese.