I'm in the middle of a repair. DW hates the first day we turn of the furnace, I guess it is just a sign of winter coming. So I should have done this earlier, but when I checked it out, no familiar 'whoooosh' of blue flames. OK, pilot is out, no problem, go through re-light procedure.... won't stay on. No problem, most likely a bad thermo-couple, I replaced one about 10 years ago, it's probably due, and I have a spare. Get it in place, still no go.
Hmmmm, a little research shows you should get ~ 20 mV from a hot thermo-couple. Got that on the new
and old one. Pointing to the gas valve. You can't really work on that, for safety reasons the pilot solenoid is integral to the gas valve, so I go online to the place I bought the blower motor from a few years ago. Long story, but shipping got messed up, and I expected it Saturday, Monday latest, and it probably won't be here until Thursday. $100 bucks for the valve, so not too bad. Managing with ~ 62F in the house. With an electric blanket, sitting around is fine though. And when I'm active it's not so bad.
On the plus side, since I had to pull the burners to get the gas valve out (ez, four screws), I got a real good look into the first row of tubes in the heat exchanger. Brushed out a little white powder and dust, and they look like new - no rust that I could see. Took apart the draft inducer to clean it and try to get oil in the sleeve bearings. That all looks good now.
And I learned from my reading, a cracked heat exchanger isn't the CO danger I always thought it was. If you think about it, the duct air is under pressure at that point, it blows
into cracks in the exchanger. The danger is that causes the flame to back-draft out of the furnace. I saw a video of that on youtube - it takes about 30 seconds for the flame detector to respond, and it was looking pretty scary by that time.
I use JB weld for many things that need to be solid/unmoving. Another great glue is the Goop glues, I use the plumbers Goop it's like silicone glue on steriods.
JB Weld has a great reputation with the DIY crowd. I'll have to try some of that Goop.
I put a new capacitor on my A/C unit every other year or so. ....
That seems odd to have it blow regularly like that. Just thinking out loud, but the motor also has some switches that kick in when the motor spins up. IIRC, they open to take the cap out of the circuit after start-up. I wonder if that switch might be bad? Seems like there should be some underlying cause.
-ERD50