How to Winterize Your Air Conditioner: A Simple Fall Checklist
When the cooling season ends, most people simply switch the thermostat to heat and forget about the air conditioner until the first hot day of next year. A little preparation in the fall, however, protects the outdoor unit from debris, moisture and pests, and makes the spring start-up far smoother. This checklist walks you through how to winterize your air conditioner safely, whether you have a central system or a window unit.
Before You Start: Is It an AC or a Heat Pump?
This is the most important question. A heat pump looks almost identical to a central air conditioner, but it heats your home in winter, so it must keep running and must never be covered or shut off for the season. Check the label on the outdoor unit or your owner’s manual. If the model is described as a heat pump, skip the winterizing steps and simply keep the unit clear of snow, ice and leaves all winter.
The steps below are for cooling-only central air conditioners and window units.
Key Takeaways
- Turn off power to the outdoor unit at the exterior disconnect to prevent accidental start-ups on warm winter days.
- Clean away leaves, grass and debris, and gently rinse the coil fins.
- Cover only the top of the unit with a breathable cover. Never wrap it in plastic.
- Remove window units, or seal and cover them from the outside.
How to Winterize a Central Air Conditioner
1. Switch Off the Power
Find the outdoor electrical disconnect, usually a small gray box mounted on the wall near the condenser. Pull the disconnect block or flip its switch to off. This stops the unit from running during an unseasonably warm day, which could damage it if water has frozen inside. It also keeps you safe while you clean.
2. Clear Away Debris
Remove leaves, sticks, grass clippings and spider webs from around and on top of the unit. Trim back plants and shrubs so there is at least two feet of clearance on all sides. Debris that sits all winter holds moisture against the cabinet and encourages rust and rodents.
3. Rinse the Coils Gently
With the power off, use a garden hose on a gentle setting to rinse dirt and pollen out of the coil fins. Spray at a downward angle, never with a pressure washer, which can flatten the delicate aluminum fins. If any fins are bent, a low-cost fin comb from a hardware store can straighten them. Let the unit dry completely in the sun before covering it.
4. Inspect the Refrigerant Line Insulation
Follow the two copper lines running from the unit into your home. The larger line should be wrapped in foam insulation. If the foam is cracked, missing or chewed, replace it with pipe insulation and UV-resistant tape. This is an easy fix that helps efficiency next summer.
5. Cover the Top, Not the Sides
A full plastic wrap traps condensation inside the cabinet, which leads to rust, mold and corroded electrical parts. It can also create a cozy nest for mice. Instead, use a breathable, mesh-sided cover or simply place a piece of plywood slightly larger than the top of the unit and weigh it down. This keeps falling ice, icicles and leaves out while letting air circulate.
6. Check the Unit Through the Winter
After storms, brush off heavy snow and make sure the area around the unit is clear. Look for signs of animals nesting underneath.
How to Winterize a Window Air Conditioner
Window units are exposed to cold drafts and moisture all winter. The best option is to remove them:
- Unplug the unit and drain any water from the base pan.
- Clean or replace the filter and wipe down the front grille.
- With a helper, remove the unit and store it upright in a dry place such as a garage or basement.
- Close and lock the window, and seal any gaps from the mounting kit.
If removing the unit is not practical, cover the exterior side with an insulated window AC cover and the interior side with an indoor cover to block drafts. Make sure the unit is unplugged.
Spring Start-Up Tips
When warm weather returns, remove the cover, clear any debris, check that the coils are clean and restore power at the disconnect. Many manufacturers recommend restoring power several hours before running the AC so the compressor has time to warm up. Then set the thermostat to cool and listen for any unusual noises during the first run.
Frequently Asked Questions
Should I cover my AC unit in winter?
Covering only the top is helpful. Fully wrapping the unit in plastic or a tarp is not recommended because it traps moisture and can attract pests.
Is it bad to leave the AC power on in winter?
Leaving power on is not usually harmful, but switching off the outdoor disconnect prevents accidental operation and is a simple safety step. Never turn off power to a heat pump that heats your home.
Do I need a professional to winterize my AC?
No. The steps above are simple DIY tasks. However, if you notice damaged wiring, oil stains around the refrigerant connections or a unit that struggled to cool all summer, book a technician for an inspection. You can also read our AC troubleshooting guides for common problems.
