The other day, the fan in our HVAC system (which I have zero knowledge about) starting going on and off in 15 minute cycles even though it was turned off. We live in San Diego and during the summer (six months ago) we had a major $2,000 repair to our A/C system, which I thought might be responsible for this.
The repair guy looked in the attic above our bedroom and announced that no, it was a $545 circuit board that had burned out and needed to be replaced, and that, oh by the way, our gas furnace was already 19 years old and most of them only last 20 years, so we should think about replacing that at a cost of an additional $2,500-$3,500. My wife immediately freaked out about this announcing that we should replace the furnace because of the imminent death that would befall us from carbon monoxide poisoning as soon as the furnace turns 20 years old.
To this I said that 1) I don’t know if modern furnaces that are gas powered even run this risk because if they did, I can’t imagine they would allow builders to put them in attics above master bedrooms in relatively new houses (ours was built in 1994) 2) I imagine that the lifespan of a furnace is related to how often you use it to crank the heat, which in San Diego is extremely rare - maybe five times a year for an hour or two. 3) I don’t trust the word of anyone who is in the business of selling furnaces that I need a new one, just like 100% of the cars that drive into a place offering ‘free brake inspections’ need new brakes.
I’m aware we should have a carbon monoxide detector in the house, which I admit we do not, and now I will buy one just to mellow out my wife, but my question is, are my assumptions correct regarding the likelihood of death by carbon monoxide? I assume these kinds of things when they occur are due to ancient furnaces that run on heating oil in cold areas with no ventilation, whereas my wife is convinced all furnaces turn into carbon monoxide spewing death machines after some length of time. What’s the straight dope?