# AC Not Cooling? 8 Things to Check Before You Call

> If your central air conditioner isn't cooling, check that the thermostat is set to Cool and below room temperature, replace a dirty furnace filter, make sure the breaker and outdoor disconnect are on, clear debris from around the outdoor unit, and look for ice on the refrigerant lines. If the lines are frozen, switch the AC off and run the fan; ice, leaks and warm air usually need a licensed technician.

Source: https://lancasterheatingandcooling.ca/ac-not-cooling-checklist/

When a heat wave rolls across Lake Ontario, a broken air conditioner can't wait. Try these safe checks first;
they fix more problems than you'd expect, and they'll help us diagnose the issue faster if you need us.

## 1. Check the thermostat

Make sure it's set to **Cool** and a few degrees below the room temperature, with the fan on **Auto**. Replace the
batteries if the display is blank.

## 2. Replace the furnace filter

Your central AC uses the furnace blower and filter. A clogged filter cuts airflow, reduces cooling and can freeze the
indoor coil.

## 3. Check the breaker and outdoor disconnect

Check your electrical panel for tripped breakers for both the furnace and the air conditioner. Near the outdoor unit
there's also a disconnect box; make sure it's on. If a breaker trips again, leave it off and call us.

## 4. Clear around the outdoor unit

Leaves, grass clippings, cottonwood fluff and plants block airflow through the outdoor coil. Keep about 60 cm (2 ft)
clear around the unit. With the power off at the disconnect, you can gently rinse the coil with a garden hose (no
pressure washer).

## 5. Look for ice

Ice on the copper lines or the indoor coil means poor airflow or low refrigerant. Turn the AC **off**, set the fan
to **On** to melt the ice (it can take a few hours), and replace the filter.

## 6. Check the condensate drain

Your AC removes water from the air. If the drain line clogs or the condensate pump fails, a safety switch may shut
the system off. Look for water around the furnace.

## 7. Open vents and close blinds

Make sure supply vents are open and return grilles aren't blocked. On very hot days, closing blinds on sunny windows
helps your system keep up.

## 8. Listen to the outdoor unit

If the outdoor fan isn't spinning, or you hear humming, buzzing or clicking without the unit starting, switch it off
and call a technician. It's often a failed capacitor or contactor, which needs a professional.

## When to call a professional

- Warm air after the checks above.
- Ice that comes back, or refrigerant lines that hiss or are oily.
- The breaker keeps tripping.
- The system is over 10–15 years old or uses R-22 refrigerant. It may be time to look at
  [AC replacement](https://lancasterheatingandcooling.ca/cooling/ac-replacement/) or a [heat pump](https://lancasterheatingandcooling.ca/heat-pumps/).

Lancaster Heating and Cooling offers [24/7 AC repair](https://lancasterheatingandcooling.ca/cooling/ac-repair/) across Hamilton, Halton and Niagara.
Call **[905-388-3333](tel:+19053883333)**. A spring [AC tune-up](https://lancasterheatingandcooling.ca/cooling/ac-maintenance/) helps prevent most of these
problems.

## AC troubleshooting questions

### Why is my air conditioner running but not cooling?

The most common causes are a dirty filter, a dirty outdoor coil, a frozen indoor coil, low refrigerant from a leak, or a failed capacitor or fan motor. Filters and debris are DIY fixes; refrigerant and electrical problems need a licensed technician.

### Why is there ice on my AC lines?

Ice usually means poor airflow (a dirty filter or closed vents) or low refrigerant. Turn the AC off at the thermostat, set the fan to On to melt the ice, and replace the filter. If it ices up again, call for [AC repair](https://lancasterheatingandcooling.ca/cooling/ac-repair/).

### Can I top up the refrigerant myself?

No. Refrigerant work must be done by a certified technician. Low refrigerant also means there's a leak that needs to be found and fixed.

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**Lancaster Heating and Cooling** — HVAC contractor serving Hamilton, Niagara and surrounding areas since 1955.
Phone (24/7 emergency): 905-388-3333 · Email: info@lancasterhvac.ca
Address: 1250 Stone Church Rd. E, Hamilton, ON L8W 2C8, Canada · Hours: Monday – Friday: 8:00AM – 4:30PM
Request a quote: https://lancasterheatingandcooling.ca/quote/