I'm thinking very possible the blower speed resistor (
HERE) got real hot. A combination of a dirty resistor and high blower motor resistance due to cold temps. The HVAC blower motor bearings are oil impregnated bronze bushings & shrink in the extreme cold and oil doesn't flow as well in the extreme cold. And therefore it takes more energy to start and run the blower in the initial period till the bearings warm up, expand like they should, and the lube warms up enough. Esp in Canadian deep winters. That extra resistance puts more strain on the resistor assembly and can make it hot for a period. That's designed into the resistor. But it could be compounded by a dirty resistor which can't cool as well. The smell would come out of the ducts. That could be what you were smelling. Just a thought.
Not an uncommon failure part. If they get dirty, they don't get the proper cooling airflow and can overheat and die. Or get knocked out by a failing blower motor. Or sometimes they just plain fail from age/corrosion, etc. You could remove your tks resistor assembly and inspect for burned areas on the board and clean if dirty. Maybe a good cleaning is all you need. Quick video
HERE.
Less likely, but possibly the blower motor is getting wonky and high resistance in the windings(??). You could ohm out the leads to check if you were so motivated. As mentioned above, a high-resistance blower can knock out a resistor or two till ya finally figure out 3-resistors later, it's actually the motor killing them. But usually it's just the resistor. If you end up needing one, a guy can buy resistors a lot cheaper on ebay ($12-$15). But for now maybe it was a one-time thing. It might be worth a quick inspection and cleaning of the existing resistor assembly. Esp now that your tk is getting to be 10yrs old.
Just a thought . Good luck!!
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