How to Troubleshoot Day & Night AC Issues Before Calling a Pro

July 15, 2025

Your Day & Night air conditioning system is designed to keep your Northwestern home cool and comfortable—until it isn’t. While it’s tempting to call a technician the moment your AC acts up, many common issues can be checked and sometimes even resolved with a few simple steps.

Before you reach for the phone (and your wallet), take a few minutes to walk through this troubleshooting guide from Day & Night. It could save you time, money, and a whole lot of frustration.

In this troubleshooting guide, we’ll cover these DIY AC repair tips:

  1. Check the Thermostat Settings
  2. Inspect the Circuit Breaker
  3. Look at the Air Filter
  4. Examine the Outdoor AC Unit
  5. Test the Airflow at Vents
  6. Check the AC for Ice or Water
  7. Sniff for Unusual Odors 
  8. Review the AC System Age and Service History
  9. When to Call a Cooling System Pro

Check the Thermostat Settings

Start with the easiest check: your thermostat. It might seem obvious, but incorrect settings or dead batteries can stop your AC in its tracks.

  • Mode: Ensure it’s set to “Cool,” not just “Fan” or “Off.”
  • Temperature: Make sure the target temperature is lower than the current room temperature.
  • Batteries: If your thermostat is battery-operated, replace the batteries. Weak batteries can cause the system to behave erratically.
  • Programmable Settings: Review any schedules or smart settings that might be overriding your manual input, especially in smart thermostats.

If the display is blank, replace the batteries or check your circuit breaker.

Inspect the Circuit Breaker

An AC unit that’s completely unresponsive might not be broken—it could just be tripped.

Locate your main electrical panel in your home and check the breaker labeled for your AC system. If it’s flipped to the “Off” or middle position, reset it by switching it fully off and then back on. 

If the breaker trips again immediately or frequently, stop here and call an HVAC repair company, like one of the dealers from Day & Night. This could indicate an electrical issue or an overloaded system.

Look at the Air Filter

A clogged air filter is one of the most common culprits behind weak airflow, frozen coils, or a system that seems to run nonstop—or ceases to run.

Pull out the air filter and hold it up to a light source. If you can’t see light through it or it is visibly dirty, it’s overdue for replacement. Most filters should be replaced every 1–3 months, depending on usage, pets, and household dust.

A dirty filter can cause the system to overheat, reduce cooling performance, and even shut down entirely.

Examine the Outdoor AC Unit

Your AC’s outdoor condenser unit needs to breathe. Over time, leaves, grass, dirt, or other debris can accumulate around the fins, preventing proper heat exchange.

  • Clear the Area: Make sure there’s at least 2 feet of clearance around the unit.
  • Inspect the Fins: Look for signs of damage or blockage. You can gently clean the fins with a garden hose (aim water at a downward angle), but don’t use a pressure washer.
  • Listen for Strange Noises: Clicking, buzzing, or grinding sounds could indicate a motor, fan, or capacitor issue. If you hear these, shut off the system and call a technician.

Test the Airflow at Vents

Walk around your home and place your hand over the supply vents. Do you feel cool air? Is the airflow strong or weak?

If one room feels warm while others are cool, it could be a blocked or closed vent, a ductwork leak, or an issue with the damper system (if you have one). Open all supply and return vents to ensure proper circulation. Never close vents in unused rooms—it can unbalance your system and reduce efficiency.

If all vents have weak airflow, the problem may lie with the blower motor or a clogged evaporator coil, both of which typically require professional service.

Check the AC for Ice or Water

If your system has been running nonstop, won’t turn on, or you notice weak airflow, inspect both the indoor and outdoor components for signs of ice or water.

  • Frozen Coils: Ice buildup on the indoor evaporator coil (inside the air handler) or on the outdoor unit often points to restricted airflow or low refrigerant levels. 
  • Condensation or Water Leaks: Water pooling around the air handler may indicate a clogged condensate drain line.

To defrost frozen coils, turn the system off completely and run the fan only for a few hours. If the ice returns, it’s time for professional help, especially if refrigerant is involved. 

If the issue is a clogged drain line, you may be able to clear it yourself. Turn the system off before attempting any repair. Ensure there is no blockage at the start and end of the drain line. Pour a cup of distilled white vinegar down the drain line and wait about 30 minutes. Vinegar is safe on pipes but can dissolve organic material clogging your drain line. Flush with hot water and repeat as needed to clear the clog fully. 

Sniff for Unusual Odors

Your nose can provide clues, too. Different smells can indicate different AC repair issues. 

  • Burning smell: May suggest electrical problems or overheating parts.
  • Musty smell: Often points to mold or mildew in the ductwork or near the evaporator coil.
  • Rotten egg smell: While rare in ACs, this can signal a natural gas leak if your system includes a gas-powered heating component. Leave the area and call your utility provider immediately.

If you detect odd odors, shut down the system until the source is identified and resolved.

Review System Age and Service History

If your Day & Night system is more than 10–15 years old, performance issues may simply be due to age and wear. Even with proper maintenance, older systems can become less efficient over time.

Also, ask yourself:

  • When was the last professional tune-up?
  • Have there been repeated repairs or the same recurring issue?

Routine maintenance can prevent many problems before they start—and extend the life of your system. But eventually age catches up, and a replacement Day & Night air conditioner may be necessary. 

When to Call a Pro

While some issues are simple to fix, others require the tools and expertise of a licensed HVAC technician. Call for service if:

  • The system still doesn’t turn on after resetting the breaker.
  • You hear grinding, screeching, or buzzing sounds.
  • Ice forms repeatedly on the coils.
  • You suspect a refrigerant leak.
  • Your AC short-cycles or runs constantly without cooling.
  • Your energy bills have suddenly spiked.

Delaying repairs can make a minor issue worse and more expensive to fix.

Stay Cool and Save Money

Troubleshooting your Day & Night AC system before calling a pro isn’t just about saving money—it’s about being an informed homeowner. Knowing the basics of how your system works helps you spot small problems before they turn into big ones and allows your technician to get to the root of the issue faster when you do call.

By following this guide, you’ll be better prepared for the next time your AC acts up—and more confident in managing your home comfort.

When DIY isn’t enough, Find a Dealer from Day & Night near you. Our network of Authorized Day & Night Dealers expands across the Northwest, including Idaho, Montana, Oregon, and Washington.