Stop
A burning smell from an AC means turn it off immediately at the thermostat and breaker, and don't run it again until inspected; call the fire department if you see smoke.
Symptoms
- Sharp, acrid, or electrical smell when the AC runs
- Smell may come from the indoor unit or the outdoor unit
- May be accompanied by unusual sounds
Likely causes
- CommonOverheating blower or fan motorA failing motor can overheat its windings or insulation and produce a burning smell.
- CommonFailing capacitor or electrical componentElectronic components can overheat and smell like burning plastic as they fail.
- PossibleLoose electrical connection generating heatA loose wire creates resistance and heat that can melt nearby insulation.
- PossibleDebris burning on a hot componentDust or debris resting on a hot motor or electrical part can smolder slightly.
What to do
- Turn the AC off immediately at the thermostat and, if the smell is strong, at the breaker as well.
- If you see any smoke, treat it as an emergency and call the fire department.
- Don't restart the system to 'test' whether the smell returns.
- Check for visible burn marks, melted plastic, or scorching around accessible panels, without touching electrical components.
- Ventilate the area by opening windows while waiting for a technician.
- Have a technician inspect the motor, capacitor, and wiring before running the system again.
When to call a pro
Call an HVAC technician immediately to inspect the motor, capacitor, and wiring before the system is used again.
Safety
Stop
A burning smell from an AC means turn it off immediately at the thermostat and breaker, and don't run it again until inspected; call the fire department if you see smoke.