Written by Jimco HVAC | Published on June 2025
Before calling for AC repair, check these 5 things first: your thermostat settings, air filter, circuit breaker, condensate drain line, and outdoor unit. Many AC problems in Naperville, IL and the surrounding 60-mile area have simple fixes that take just a few minutes.
This guide walks you through each check step by step. You will learn what to look for, what it means, and when you actually do need a professional. Knowing the difference can save you a $75 to $150 service call fee.
Check Your Thermostat Settings First
It sounds obvious, but thermostat issues cause a surprising number of AC service calls. Before assuming your system is broken, verify a few key settings.
- Make sure the system is set to COOL, not HEAT or FAN ONLY.
- Set the temperature at least 3 to 5 degrees below the current room temperature.
- Check that the fan is set to AUTO, not ON. The ON setting runs the blower constantly, which can feel like the AC is not cooling.
- Replace the thermostat batteries if the display is dim or blank. Most thermostats use AA or AAA batteries.
- If you have a smart thermostat like a Nest or Ecobee, check the app for any scheduled overrides or vacation modes.
In Naperville summers, indoor temps can climb fast during heat waves. A thermostat stuck in the wrong mode means your system runs but never actually cools. This is one of the most common things to check before calling AC repair.
Inspect Your Air Filter
A clogged air filter is the number one cause of reduced AC performance and is completely free to fix if you have a spare filter on hand. A dirty filter blocks airflow, forces your system to work harder, and can even cause the evaporator coil to freeze.
Here is what to look for when you pull your filter out:
- A light gray or dusty filter is normal. Replace it and see if airflow improves.
- A filter packed with dark gray or black debris means it is long overdue for a change.
- If your filter looks clean but your AC still runs poorly, the issue is likely elsewhere.
- Standard 1-inch filters should be replaced every 30 to 60 days during heavy summer use.
- Thicker 4-inch media filters can last 6 to 12 months depending on your home and pets.
Homes in Naperville and surrounding areas like Aurora, Oswego, and Plainfield often deal with high pollen counts in spring and summer. That extra airborne debris clogs filters faster than you might expect. Changing your filter regularly is one of the easiest things to check before calling AC repair.
Reset Your Circuit Breaker
If your AC is not turning on at all, a tripped breaker is a very common reason. Your air conditioner runs on a dedicated circuit, and that breaker can trip during a power surge or if the unit is overloaded.
Go to your electrical panel and look for the breaker labeled AC, Air Handler, Condenser, or Heat Pump. A tripped breaker sits in the middle position between ON and OFF. Push it fully to OFF first, then flip it back to ON. Wait a few minutes before trying to run your AC again.
If the breaker trips again immediately or repeatedly, stop resetting it. A breaker that keeps tripping is a sign of a deeper electrical issue. That is the point where you should call a licensed technician. Jimco HVAC handles exactly this type of electrical and HVAC crossover diagnosis for homeowners across the Naperville area.
Look at Your Outdoor Unit
Your outdoor condenser unit does the heavy lifting of releasing heat from your home. If it is blocked, dirty, or shut off, your AC cannot cool properly.
| What to Check | What It Looks Like | What to Do |
|---|---|---|
| Vegetation overgrowth | Grass, weeds, or shrubs growing within 2 feet of unit | Trim back and clear at least 2 feet on all sides |
| Debris inside unit | Leaves, cottonwood, or dirt packed in fins | Rinse gently with a garden hose, fins pointing down |
| Disconnect switch off | A pull-out box near the unit that is removed or turned off | Push the disconnect back in or flip to ON |
| Ice on refrigerant lines | White frost on the copper pipes running to the unit | Turn system to FAN ONLY for 2 hours to thaw, then call a tech |
| Fan not spinning | Unit is humming but the top fan blade is not moving | Turn off immediately and call for service |
Naperville and the broader Chicago metro area sees heavy cottonwood seed release in late spring and early summer. That fluffy white debris clogs condenser coils fast. A quick rinse every few weeks during that season makes a real difference.
Clear the Condensate Drain Line
Your AC removes humidity from the air as it cools. That moisture drips into a drain pan and exits through a condensate drain line. When that line clogs, the pan overflows and many systems have a safety switch that shuts the whole unit off.
Here is how to check and clear your condensate drain:
- Find your indoor air handler, usually in a utility closet, attic, or basement.
- Locate the white PVC drain line that exits the unit, often running to a floor drain or outside.
- Check the drain pan under the unit. If it has standing water, the line is likely clogged.
- Find the clean-out access port on the drain line. It looks like a small cap on a T-shaped fitting.
- Pour a cup of distilled white vinegar into the port. Let it sit for 30 minutes and flush with water.
- For stubborn clogs, use a wet-dry vac at the outdoor end of the drain line to suck out the blockage.
Algae growth is the most common cause of drain clogs in humid summer months. Pouring vinegar into the drain line once a month during cooling season prevents most clogs before they start. This is a low-effort step that too many homeowners skip.
Compare: DIY Fix vs. Professional Repair
After going through the five checks above, you may still have an AC that is not working right. Knowing when to stop troubleshooting and call a pro saves you time and prevents accidental damage.
| Symptom | Likely DIY Fix | Call a Tech If… |
|---|---|---|
| AC not turning on | Reset breaker, check thermostat batteries | Breaker keeps tripping or display stays blank |
| Weak airflow | Replace dirty air filter | Filter is clean but airflow is still low |
| AC runs but won’t cool | Clear outdoor unit, check thermostat mode | Ice on lines or refrigerant hissing sound |
| Water leaking indoors | Clear condensate drain line | Pan is full and unit won’t restart after clearing |
| Loud banging or grinding noise | None, turn off unit immediately | Always, right away |
| Burning smell | None, turn off unit immediately | Always, this is a safety issue |
Jimco HVAC serves Naperville and communities within 60 miles including Joliet, Bolingbrook, Wheaton, Batavia, and Elgin. When the checks above do not solve your problem, our team can diagnose and repair most AC issues the same day.
FAQs on Things to Check Before Calling AC Repair
How do I know if my AC problem needs a professional or if I can fix it myself?
If the issue is a dirty filter, wrong thermostat setting, tripped breaker, or clogged drain line, you can usually fix it yourself in under 30 minutes. If your unit is making grinding or banging noises, smells like burning, or has ice on the refrigerant lines, turn it off and call a licensed technician right away.
Why is my AC running but not cooling the house?
The most common reasons are a dirty air filter blocking airflow, a clogged condenser coil on the outdoor unit, or low refrigerant. Check your filter and outdoor unit first. If both look fine, you likely have a refrigerant or mechanical issue that requires a professional.
Can a clogged air filter cause my AC to stop working completely?
Yes. A severely clogged filter restricts airflow so much that it can cause the evaporator coil to freeze. When the coil freezes, the system may shut itself off as a safety measure. Replace the filter and let the coil thaw for a few hours before restarting.
How often should I check my AC before calling for repairs in the Naperville area?
Check your air filter monthly during summer months. Inspect your outdoor unit every few weeks, especially during cottonwood season in late spring. A quick annual tune-up before the cooling season starts is the best way to catch small issues before they become expensive repairs.
What should I do if my circuit breaker keeps tripping when I run the AC?
Do not keep resetting a repeatedly tripping breaker. This is a sign of an electrical overload, a short circuit, or a failing compressor. Turn the AC off and contact a licensed HVAC and electrical professional. Continuing to reset the breaker can cause serious damage or a fire hazard.
Is it normal for water to leak from my indoor AC unit?
Small amounts of condensation around the unit can be normal, but standing water in the drain pan or visible dripping is a sign of a clogged condensate drain line. Try clearing the line with vinegar and a wet-dry vac. If water continues to accumulate after clearing the line, call a technician to inspect the drain pan and safety float switch.
Wrap Up and Next Steps
Going through these 5 things to check before calling AC repair takes less than 30 minutes and can save you a service call fee and hours of waiting in the heat. Start with the thermostat, filter, and breaker. Then move to the outdoor unit and condensate drain.
If you have worked through every check and your AC is still not performing right, it is time to call in a pro. Jimco HVAC serves Naperville, IL and communities up to 60 miles out, including same-day AC repair during peak summer season. Call us at (708) 304-8687 to schedule a diagnostic visit or get a quote.