Ok, not really Corolla..or even car related..but an interesting DIY-kinda project. My 12yo Carrier Furnace wouldn't fire up.
The symptoms: Turn on furnace...Blower motor starts and runs for 3 mins. Then draft induction motor starts. After about 1 min the Hot surface ignitor SHOULD start glowing..but didn't..Hmmmm...
My casual observations made me think that I just needed a new HSI..but after getting a new one and installing it, still the same problem.
Now to start hunting what else could be the problem.
NOTE: GFA furnaces are definetly DANGEROUS and should be approached & diagnosed with extreme care!
I figured, If i couldn't figure it out, I'd just call a serviceman and bite the bullet. But I wanted to be sure it wasn't a $5 part that I'd have to end up paying $150..so off I went.
Going to all references I could find on operations & parts on GFA, I found most modern furnaces have something called a Pressure switch, which reads the pressure on the flue. If there is sufficient negative pressure, the switch will close, indicating there is exhaust for the burner gases ( CO! ). It reads the pressure in the flue via a 1/4 tube. Sometimes, these tubes get blocked or develop a kink..but not in my case.
References said to just remove the switch ( pic below ) and test for continuity with a multimeter. Just suck on the tube and test. If the switch is still good, the contact will close when there's pressure. Mine worked fine.
Next, It is indicated that one should test the pressure while the draft induction motor is running. To test,
you need a magnehelic gauge, which I bought on eBay for $12. After about 10 days, I tested the pressure
and it was ok too! Hmmm..now what?
After scouring various forums and websites, I found a great DIY site which sells appliance parts. There was
mention of a couple of 'limitor switches' that must be functioning properly to send voltage to the circuit board before the controller will fire up the HSI. It was BRIEFLY mentioned that one of the limiter sensors/switches has a 'reset' button in the middle. I found the sensor, and found the button. Pressed the reset button...and tried it..VOILA..it fired up perfectly.
I emailed the webmaster of the site thanking him, and asked what that limitor switch is for? He said it's a temperature switch. If the temp in the flue goes above a certain temp, the switch will disengage and prevent the furnace from starting ( presumably, another safetly precaution if the flue becomes overheated ).
He suggested I look down the chimmney for any obstructions ( Bird or Wasp nest ). I did so, took my most powerfult flashlight but found nothing. A clear shot all the way down to the furnace.
Well, that's my story. I still don't know what caused the temp limitor to pop, but the furnace has been going for about 3 weeks now no problems.
Come to think of it, I vaguely remember the day the furnace stopped firing up...back in April, during a VERY windy day. I suppose its possible a huge gust of wind blew down the chimmney and back-pressured the exhaust gas enough to cause the breaker to trip. FYI.
BTW, here's the website for diagnosing and repairing. Arnold is a nice guy: