Note to self: when going to bed, and walking past a heating vent that is blowing cold air, double check that the furnace is working.  52 degrees in the house this morning, and it isn't that cold out (27 or so).The fan is on constantly, but the ignition isn't turning on, so it seems that the furnace thinks it is in the cool-down cycle, and so isn't turning on the gas.  Hopefully we'll figure it out soon.
Posted by Jon Daley on February 14, 2007, 8:39 am | Read 4085 times
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Ugh! Are you staying warm enough with that space heater? If not, come over!

Posted by serina on February 14, 2007, 3:08 pm

This snow day has been pretty fun. Daddy's home, though he has been working on the furnace all day. When I got too cold, we went out for some vigorous snow shoveling and I got all warm again. Now of course I'm at the computer again so my fingers are cold, but I think after this I"ll head down and see the furnace progress and warm my fingers with a mug of tea.

Yes, it's cold in here, but it's an adventure and we have layers (Jonathan thought it was pretty funny to wear two pairs of pants!) and the space heater and a teakettle and an oven to bake granola in. I'm planning on some nice whole grain cornbread soon, too. (: Thanks, Serina! It might be worse to drive in the ice than to just stay home by our space heater...

Posted by joyful on February 14, 2007, 3:36 pm

Well, I should have gone with my first guess. I spent all day trying to figure out the circuitry - I guess I must not have been patient enough during one test, so I stopped looking at one limit switch.

But, finally, I traced it out enough to be pretty sure that it had to be that switch.

And now it is too late to get a replacement in Pittsburgh (and lots of places are closed due to the weather), and I can't find one online. A pair of pliers shorting two wires is doing the trick for now.

Posted by jondaley on February 14, 2007, 5:03 pm

So, for the next guy who is working on a Janitrol/Goodman (GUN075-3B) and you have the blower on constantly, but there isn't a spark, and so just cold air is blowing out, grab a voltmeter, and check the voltage at the input to the thermostat, and see if you have 24 volts AC there. (on my unit the wire is red, but that probably isn't totally standard)

If not, check the two orange wires going to the main limit switch on top of the flame. If there is 24 volts at one of them and not the other, the sensor thinks it is too hot, so if it isn't hot, then it is broken.

If you unplug the sensor (Part number 13700-08, L160F-30), when it is cold it should be shorted, and when it gets above 160 degrees it should open.

You can take the two orange wires and short them together as a temporary fix.

The good news is that I think the part will only cost $13 or so.

Posted by jondaley on February 14, 2007, 5:12 pm

Second note to self: when you use a pair of pliers to short two wires together, as you put the furnace back together again, you should make sure that the pliers don't touch any other metal.

If that should hypothetically happen, you should be prepared to replace the fuse with a regular 5 Amp car-type fuse. Pep Boys has them for $2.39. Good thing that didn't happen to me. :)

Pliers are now electrical-taped, so it shouldn't happen again.

Third note: when you neighbor sees you going out, and asks you to pick up a bag of rock salt, realize that when the city is halfway shutdown due to the weather, that everyone else already bought all of the salt in three different stores, and people will just laugh at you when you ask if they have any left.

Posted by Jon Daley on February 14, 2007, 9:00 pm

Wait...what didn't happen shouldn't happen again.... Makes sense to me; then again, I'm feeling rather tired and punchy about now. But warm, so I can't complain.

Posted by SursumCorda on February 14, 2007, 10:07 pm

On Thursday, Jon bought and installed the replacement part and the furnace has worked wonderfully since.

Posted by joyful on February 17, 2007, 9:32 am