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Does the main blower that blows heat through house appear to be running as normal?
and when the furnace shuts down is there a light on a circuit board that blinks?
is this light on the gas valve or on the circuit board in bottom?
Thank you. Now when first started this light should be solid but when it faults it blinks a pattern...like 3 for example...and repeats. Do you know what yours does?
what is blink on shut down?
on this unit bright/dim, bright dim is normal.
a one blink that repeats is overtemp limit fail meaning it is running too hot. Then a limit opens until cooled and then lets it try again.
This can be air restriction (filters)
Bad blower (slowing down)
Blockage in duct ( saw a plastic bag sucked in one time)
ac coil plugged on top of furnace if present.
Basically it is an overheat saying not enough air flow.
Start with anything that can slow air in the duct...on these units I have even pulled the blower to remove debris/dust.
Since you smelled something hot, I am betting the limit is doing its job and the furnace is actually running to warm.
make sure blower in bottom running strong
just return back here for follow up.
Rate service to move off the active list for now.