Originally Posted by jonandabby
I happened to be in the basement yesterday for the start of one of the "incidents." Here is the chronology:
Our heater (a Carrier combination gas furnace/A/C) is about 17 years old. When the heat kicks on, it goes in phases. There is a minute or so cycle where it sounds like there is a small fan kicking on and the pilot light and burners are starting to heat up. After about a minute, the blower starts.
Last night, I heard the sound of an electrical circuit turning on, and after about 20 seconds it turned off. The blower never kicked on, and it sounded like the “startup” phase didn’t finish. A few other things I noticed - we have a humidifier that turns on ONLY when the heater is on. After that circuit/pilot sound, the humidifier started to run and didn't turn off although the blower never started. (coincidentally or not, the carpet near the heater was soaking wet. I think that the humidifier was running when these things keep happening, and overflowed onto the carpet. But that’s just my theory.)
I went up to the thermostat, a digital Honeywell connected to the power from the heater. The thermostat was blank - the time and temperature was off. I tried to turn the switch from auto to "on" to manually switch on the heater, and there was no response (We'd typically hear the sound of the heater's initial cycle turning on).
I went upstairs, AND THE SMELL (like metallic burning rubber for those new to this….) HAD STARTED. It was very strong.
I went down to the basement to see if the heater was smoking or anything, and it wasn't. The smell wasn’t particularly noticeable next to the heater. I was down there for about 5 minutes, and went back to the thermostat, which had switched back on. I played around with the temperature and fan (which went on). Initially, the system was only blowing air that wasn’t being heated. After a period of about 20 minutes, I was able to get the heater to start blowing hot air. The odor coming from the vents had traces of the smell for about an hour, and then the smell had mostly gone away.
It apparently happened again this morning – my wife called and told me she detected the odor again.
Does the new information help? Between the increasing frequency (at least once a day, where it used to be every week or so) and the quirkiness with the humidifier and the blank thermostat, this seems less like a duct problem and more like an electrical problem to me. We did just have the ducts cleaned, too. I'd hope that the cleaning would have gotten out any dead animals in the ducts. But I know nothing….