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4 Reasons Your Outdoor AC Unit May Smell Like Smoke

Air Condition Outside
It's easy to find advice about why you may have a bad smell coming from your AC vents and what to do about it. But what about the outdoor unit? If you go outside to check up on a problem and find a burning smell or some other bad odor, what does it mean? Here's what might be happening when your unit smells like smoke or burning.

1. Electrical Failure

One fairly basic reason for a burning smell could be an electrical short, arc, or bad connection. Wiring problems sometimes happen on their own, and other times they're caused by power surges or by pests such as mice, rats, or even snakes.

Either way, don't try to keep using the system; shut off the electricity immediately, and then contact your HVAC contractor.

You should never take any electrical issue lightly, and an AC electrical problem is no different. Although the unit is outside your house, it can still cause a house fire or electrocution.

2. Capacitor Problem

A blown capacitor can also smoke and give off a burning odor. A capacitor is a part that functions like a giant battery, giving a little extra power to the motor when needed (during startup if it's a start capacitor, or while the motor is running if it's a run capacitor. Many units have both).

If your unit has also been giving off signals such as shutting off suddenly, struggling to start, or running inefficiently and spiking your energy bills, a capacitor problem could be at issue here. Unfortunately, if you also smell a smoky or burning odor, the capacitor is likely completely dead. In this case, shut off the unit and call a repair technician.

A failed run capacitor can also mean a motor ends up overheating, which could be another reason for a burning or smoking smell.

3. Motor Bearing

Sometimes a motor bearing will give out and cause an overheating problem that then creates smoke and smells awful. This issue is often distinctive because the motor can make a terrible screeching or banging, clanking type noise when the bearing is going bad. 

You may also smell this odor from inside, or you may just notice the screeching or clanking sound before going out to check and noticing the smell. The compressor motor and the fan motor can both develop this issue. While the compressor is usually more expensive to fix, neither one should be ignored.

4. Overheating From Overwork

Either the compressor motor or the AC fan motor can cause a smoky or overheated smell if overworked. One reason for excess strain on these motors is poor airflow, often caused by clogged filters, weeds around the unit, and debris stuck in the fan. And if you run the AC without a working fan, the lack of fresh air can cause overheating and smoke smells as well. 

Other contributing factors to poor airflow can include:
  • Coolant leaks
  • Leaky, narrow, or clogged ducts
  • Indoor vents blocked (such as by furniture)
  • Lack of maintenance
  • Problems with the thermostat
When cutting the grass and weeds around your outdoor unit, you should also be careful that the grass clippings don't get stuck in the fins on the unit’s sides and then dry there. This can block airflow too. 

These are just four reasons your unit may give off a smoking, overheated, or burning smell. Because of the electrical danger involved with handling these issues, you should never try to repair a smoky-smelling unit yourself. Instead, switch off the power and get in touch with a reputable contractor at once.

Action Plumbing & Heating Maintenance provides a full range of HVAC repair services including emergency visits. Give us a call if you need HVAC servicing in the Santa Rosa area.