Merry Christmas!
We have family on their way to spend the holidays with us and guess what? Woke up to a chilly house.
Gas furnace, Trane model TDE060A936L1, around 19 years old.
When heat called for the draft fan and blower fan run, just no fire.
I've been thinking that one day soon I'll need a new system and will likely go with some form of heat pump/furnace which would add AC (no AC now, live in Pacific Northwest where many homes have never had AC).
But would like to know if this is something I can troubleshoot and repair myself, to hire a pro, to even invest money into this unit or just go new, and of course its winter and Christmas, though we can get by with fireplace and space heaters for awhile.
Your advice needed and appreciated!

 

Look thru the blower door. See if there is a fault code flashing.
Try disconnecting power and reconnecting. Watch what faults are shown.

 

4 blinks
"Thermal Protection Device Open" is what is says on the sticker on the circuit board for 4 blinks. Filter is clean, duct grilles open.
Sounds like this one means the brains think something is too hot, is that right?

 

Yes.... a four flash code is an open high heat limit.

So did turning off the power and turning it back on clear that code ?
Did the furnace try to fire up again ?

 

No. I turned off power to furnace. Waited a bit. Turned it back on and again, draft fan and blower run, but no fire. And code still flashing 4.

 

That furnace will have two manual reset flame rollout limits. It is a bad sign for one of these to trip.

 

That means you'll need to check the limit switches with a meter to find out which one is open. It may be a roll out switch right above the burner opening. Typically those sensors have a little red button on the back to reset them.

If one of those tripped..... you must get the furnace checked out. You could have a problem with the burner over firing, flue blockage, comprimised heat exchanger.

 

Thanks, guys. Appreciate the help. If/when I get it figured out I will update this.

 

Follow up:
Since the draft inducer blower bearings sounded noisy, I ordered a replacement. And I couldn't prove any of the temp limit switches was failing, but I ordered the one that is located inside the where the heat exchanger is. Waited a couple days, and when the parts arrived, I turned furnace back on and it was working normally no trouble lights flashing (this was before I did any work on it!) A couple days earlier I had turned power off to it a couple times for 15 mins or so to see if things would re-set and it hadn't worked. Hmmm.
Anyway, I went ahead and replaced the draft inducer fan assembly (much quieter now) that limit switch. For a couple days now all is working normally. Time will tell, but can't figure out what happened to start this whole thing.