toxcrusadr
Omelette au Fromage
We have a 1989 York Stellar Plus 90+% efficient gas furnace. It has a separate combustion air blower. It’s in pretty good shape for its age because we use the woodstove daily. A couple weeks ago it started acting funny – the startup cycle would hang up and it wouldn’t fire up. I had the guy out on a Saturday (don’t ask me what that cost - ). He said the flame sensor was dirty, cleaned it with emery cloth and it started right up. 2 minutes with sandpaper. Dammit. Anyway now it’s doing it again.
The startup cycle is as follows:
Combustion air fan (vent fan) on
Hot surface igniter glows
Flame comes on
Big blower starts up
Igniter turns off
There are interlocks, pressure switches etc. at every stage of course. What I couldn't make sense of the first time around is that sometimes the igniter would glow but the gas wouldn’t start up, and other times it wouldn't glow at all, and it would just sit there with the vent fan blowing forever. But, when he cleaned it, it ran consistently for a couple weeks, so I put that little inconsistency behind me.
So it's doing it again, this time no igniter glow at all. Now that I know how to clean the sensor, I’m doing that right after work today. Possible the sensor is bad and needs to be replaced, or the furnace is not burning cleanly and it's gunked it up again.
But it seems to me that if the flame sensor is bad, the igniter would still come on, and maybe the flame should even light up. The sensor is not really doing anything until the flame comes on, right? So I wonder if there isn’t a bad pressure switch. There are two pressure switches, maybe the one that senses that the vent fan is running is not working, so it doesn’t proceed to light up the flame?
Suggestions happily considered. The wife wants me to just call it in, but I'm not confident they're going to fix it this time either, and/or might soak me again to get it done.
Should I have to pay a second service call fee since the repair didn't stick?
The startup cycle is as follows:
Combustion air fan (vent fan) on
Hot surface igniter glows
Flame comes on
Big blower starts up
Igniter turns off
There are interlocks, pressure switches etc. at every stage of course. What I couldn't make sense of the first time around is that sometimes the igniter would glow but the gas wouldn’t start up, and other times it wouldn't glow at all, and it would just sit there with the vent fan blowing forever. But, when he cleaned it, it ran consistently for a couple weeks, so I put that little inconsistency behind me.
So it's doing it again, this time no igniter glow at all. Now that I know how to clean the sensor, I’m doing that right after work today. Possible the sensor is bad and needs to be replaced, or the furnace is not burning cleanly and it's gunked it up again.
But it seems to me that if the flame sensor is bad, the igniter would still come on, and maybe the flame should even light up. The sensor is not really doing anything until the flame comes on, right? So I wonder if there isn’t a bad pressure switch. There are two pressure switches, maybe the one that senses that the vent fan is running is not working, so it doesn’t proceed to light up the flame?
Suggestions happily considered. The wife wants me to just call it in, but I'm not confident they're going to fix it this time either, and/or might soak me again to get it done.
Should I have to pay a second service call fee since the repair didn't stick?