How to winterize an AC system
Southern California winters are mild, but rain, cool nights, coastal salt air, and Santa Ana winds can still damage an outdoor condenser, rooftop unit, or mini split. Proper AC winterization prevents corrosion, pest intrusion, and electrical issues, and it helps with warranty compliance and insurance requirements that often call for documented care by a licensed HVAC professional. Below is a practical guide tailored to our climate and building types.
What winterizing an AC actually means
“Winterizing” protects cooling equipment during the off-season, without trapping moisture or disabling safety features. The steps vary by system type:
- Central air conditioner (cooling-only): prepare the outdoor condenser and the indoor air handler or furnace connections.
- Heat pump: do not shut it down in winter; it heats your home. Winterizing focuses on cleaning, drainage, and clear airflow.
- Mini split: similar to heat pumps, many run year-round; protect the outdoor unit and keep lines and drains clear.
- Commercial rooftop unit (RTU): add wind and debris controls and verify roof drainage and service-clearance.
Step-by-step winterizing checklist (cooling-only condensers)
- Shut off and lock out power. Turn off the disconnect at the condenser and the breaker. This prevents accidental starts and protects the compressor during cold snaps.
- Clear debris and clean the coil. Gently remove leaves and rinse the coil from the inside out with low-pressure water. Avoid high-pressure washers that bend fins.
- Dry thoroughly. Let the unit air-dry before any covering. Trapped moisture can cause corrosion and mildew.
- Inspect refrigerant lines. Replace cracked insulation on line sets. UV-rated insulation helps in Los Angeles County sun and Santa Ana winds. Do not cut or open refrigerant lines.
- Check the condensate drain. Flush algae from the condensate drain or pump. Proper slope and a clean trap prevent backups during the first spring start.
- Examine electrical connections. Look for scorch marks, brittle wires, or a pitted contactor. Electrical repairs should be done by a licensed HVAC professional.
- Protect against corrosion. In coastal zones with salt air, rinse more often and consider an approved anti-corrosion coating on exposed metal.
- Use a breathable cover. Do not wrap the unit in non-breathable plastic. A top cover or breathable condenser cover prevents debris entry while allowing moisture to escape. Secure it against wind.
- Maintain clearance. Keep 2–3 feet of open space around the unit. Trim shrubs and remove items that can strike the coil in high winds.
- Document the work. Photos and notes support warranty compliance and, if ever needed, insurance requirements for HVAC claims.
Heat pumps and mini splits: do this instead
Because heat pumps and many mini splits provide winter heating, leave power on. Focus on:
- Keep the outdoor coil clean so defrost cycles work properly.
- Verify condensate management for wall cassettes and floor units; clear the drain pan and lines.
- Ensure snow or windblown debris (in mountain areas) cannot block airflow. In windy zones, add a wind baffle approved by the manufacturer.
- Check line-set insulation and mounting brackets on balconies or walls.
SoCal specifics to consider
- Santa Ana winds: Secure light covers and check rooftop unit panels. Debris screens can reduce leaf intake without choking airflow.
- Coastal corrosion and salt air: More frequent coil rinsing and protective coatings extend condenser life.
- Wildfire ash: Ash is fine and conductive; rinse coils and replace filters sooner.
- Heavy rains: Confirm the unit sits above grade and that roof drains near RTUs are clear.
Common mistakes to avoid
- Wrapping the condenser in airtight plastic, which traps moisture and causes mold and corrosion.
- Powering down a heat pump you rely on for heating.
- Using a pressure washer that flattens coil fins and reduces performance.
- Covering the unit so tightly that it becomes a rodent habitat.
- Ignoring electrical hot spots or oil stains that signal a refrigerant leak—both require a licensed HVAC professional.
When to bring in a licensed HVAC professional
Call a pro for any refrigerant issue, electrical repair, compressor or fan motor concerns, chronic tripping breakers, or if the unit short-cycles. Many equipment warranties and commercial and homeowner insurance requirements expect maintenance and repairs to be performed and documented by a qualified technician. For rooftop units, professional service also addresses roof safety, fall protection, and warranty compliance.
Quick winterizing summary
- Shut off and lock out power (cooling-only systems).
- Clean and dry the condenser coil; replace damaged line-set insulation.
- Flush the condensate drain; verify slope and traps.
- Use a breathable, wind-secured top cover—never a sealed wrap.
- Rinse more often in coastal areas to reduce coastal corrosion from salt air.
- Leave heat pumps and mini splits energized and keep airflow paths clear.
About #1 AC Guys
#1 AC Guys is a family-owned HVAC company serving Los Angeles County and nearby areas including Orange County, Ventura County, and Western Riverside County. Our fourth-generation family of engineers brings 80+ years of engineering experience to residential and commercial systems, with a focus on large and complex projects. Our mission is healthy air at home for healthy life.
Our engineers trained at the factory with Fujitsu (Japan), Mitsubishi Electric (Thailand), Midea (China), Gree (China), and Haier (China). We support solutions for central air conditioners, mini split systems, heat pumps, and commercial rooftop units with a strong emphasis on safety, code compliance, and warranty alignment.
Cities we commonly serve
Across Los Angeles County and neighboring regions, we frequently work in Los Angeles, Pasadena, Long Beach, Santa Monica, Glendale, Burbank, Anaheim, Irvine, Huntington Beach, Fullerton, Thousand Oaks, Oxnard, Ventura, Corona, and Riverside.
FAQs
Do I need to cover my air conditioner?
Use a breathable condenser cover or a top cover to block debris while allowing moisture to escape. Avoid full plastic wraps.
Should I shut down a heat pump in winter?
No. Heat pumps heat your home in winter. Keep power on, keep the coil clean, and ensure adequate airflow.
How often should I winterize?
Perform a light winterization after the cooling season and a startup check in spring. Coastal homes may need more frequent rinsing to combat salt air.
What about commercial rooftop units?
Secure panels, verify roof drainage, clear debris, and document service. Insurance requirements and warranties often expect licensed HVAC professional maintenance.
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