Why does my heater smell like burning?

Sorting normal smells from warning signs

Furnaces sit idle all summer collecting a film of dust on the heat exchanger and burners. The first few heating cycles of fall burn that film off, producing the familiar faintly scorched odor that clears quickly. Other smells carry different messages. An acrid plastic or electrical odor suggests overheating wiring, a failing blower motor, or a slipping belt. A persistent dusty burn deep into the season often means a clogged filter is forcing the furnace to run too hot. A musty smell points to moisture or mold rather than burning, and any rotten-egg sulfur odor is the gas company's added odorant, which means leave the house and call the gas utility from outside.

What you can do before picking up the phone

• ✓If the smell is sharp, electrical, or plastic-like, turn the system off at the thermostat and leave it off
• ✓Replace the filter if the odor is a dusty burning that has not faded
• ✓Make sure nothing is stored against or on top of the furnace, especially anything flammable
• ✓Check that supply registers are not roasting dust trapped in carpet or drapes against them
• ✓For any gas odor, do not operate switches; exit and call the gas utility immediately

Why electrical and overheating smells need a pro

Burning-component odors usually mean something is hotter than it should be, and the fix involves motors, wiring, or safety controls that are not homeowner territory. A technician can test the blower motor, inspect the wiring and limit switches, and confirm the heat exchanger is sound, since chronic overheating is one of the things that cracks exchangers. PJ MAC HVAC, family owned with a 5.0-star rating from 176 Google reviews, handles this diagnosis on all furnace brands and fuel types.

A burning smell at 2 a.m. is exactly why PJ MAC HVAC keeps its emergency line open around the clock.