Key Takeaways
- A dirty or blocked air filter is the #1 cause of reduced cooling — check and replace it first before anything else.
- Most AC systems installed before 2020 were sized for BC's historically mild summers, not today's 38°C+ heat waves.
- Low refrigerant requires a licensed technician — don't delay, as running low can destroy the compressor.
- Duct leaks can waste 20–30% of your cooling before it reaches the living space.
- If the system is more than 15 years old and struggling, a replacement is often more cost-effective than repeated repairs.
It's 34°C in Abbotsford, your air conditioner has been running for six hours straight, and your living room is still 28°C. You're not imagining it — your AC is running but it's not keeping up. This is one of the most common calls we receive at Grove Mechanical during BC heat waves, and the cause is almost never a single catastrophic failure. It's usually one of seven predictable problems, several of which you can address yourself.
1. The System Was Never Sized for Extreme Heat
Most air conditioning systems installed in the Lower Mainland before 2020 were sized for BC's historically mild summers — not for the 38°C+ temperatures that have become increasingly common since the 2021 heat dome. An AC system that was correctly sized for average summer conditions may be genuinely undersized for the peak temperatures your home now experiences.
What to do: Have a Manual J load calculation performed to determine the correct system size for your home. If your current system is genuinely undersized, upgrading to a larger unit — or adding a supplemental ductless mini-split in the hottest rooms — is the right long-term solution.
2. A Dirty or Blocked Air Filter
This is the most common cause of reduced cooling performance, and it's entirely preventable. A clogged air filter restricts airflow through the system, reducing the volume of air that passes over the evaporator coil. A severely blocked filter can reduce your system's cooling capacity by 20–30% and, in extreme cases, cause the evaporator coil to freeze — which completely stops cooling until the ice melts.
What to do: Check your filter right now. If it's grey or visibly clogged, replace it immediately. During heat waves, check your filter weekly.
3. The Outdoor Unit Is Blocked or Overheating
Your AC's outdoor condenser unit works by rejecting heat from your home into the outdoor air. When the outdoor unit is blocked — by overgrown shrubs, debris, or accumulated dirt on the condenser coils — it can't reject heat efficiently. During heat waves, the outdoor temperature itself creates a challenge: the hotter it is outside, the harder it is for the condenser to reject heat.
What to do: Clear at least 60 cm of clearance around all sides of the outdoor unit. Gently rinse the condenser coils with a garden hose to remove dust and cottonwood fluff. Don't use a pressure washer — it can damage the fins.
4. Low Refrigerant (Refrigerant Leak)
If your system has a refrigerant leak, the reduced refrigerant charge means less heat transfer capacity. Low refrigerant is often accompanied by ice formation on the refrigerant lines or evaporator coil, a hissing or bubbling sound near the indoor unit, and a noticeable drop in cooling performance over time.
What to do: This requires a licensed HVAC technician. Call Grove Mechanical. We'll diagnose the leak, repair it, and recharge the system to the correct level. Don't delay — running a system with low refrigerant can damage the compressor.
5. Ductwork Leaks or Poor Insulation
In homes with central ducted AC, a significant portion of cooling can be lost before it reaches the living spaces if the ductwork has leaks or passes through unconditioned spaces (attics, crawlspaces) without adequate insulation. Studies suggest that the average home loses 20–30% of conditioned air through duct leaks.
What to do: A duct leakage test can quantify how much air your system is losing. Duct sealing with mastic or metal tape can recover a significant portion of lost cooling capacity.
6. The System Needs a Professional Tune-Up
An air conditioning system that hasn't been serviced in 2–3 years will underperform compared to a well-maintained system. Over time, the evaporator and condenser coils accumulate a layer of dust and dirt that acts as an insulator — reducing heat transfer efficiency. A professional AC tune-up typically restores 10–15% of lost efficiency.
What to do: Book an annual AC tune-up every spring before cooling season. If your system hasn't been serviced in more than two years, a tune-up is the first step before considering any other repairs or replacements.
7. The Home Itself Is Letting in Too Much Heat
Sometimes the problem isn't the AC system at all — it's the building. A home with poor insulation, single-pane windows, or significant air leakage will gain heat faster than even a correctly sized, well-maintained AC system can remove it. West-facing rooms with large windows are particularly vulnerable during afternoon heat waves.
What to do: In the short term, close blinds and curtains on west and south-facing windows during afternoon hours. Seal obvious air leaks around doors and windows. In the longer term, consider window film, exterior shading, or insulation upgrades.
When to Call a Professional
If you've checked the filter, cleared the outdoor unit, and the system is still struggling, it's time to call Grove Mechanical. We serve Surrey, Langley, Abbotsford, Chilliwack, Mission, Maple Ridge, and surrounding areas; request service to confirm the appropriate next step and current scheduling availability.
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Frequently Asked Questions
Why can't my AC keep up during a Fraser Valley heat wave?
The most common reasons are: a dirty air filter restricting airflow, an undersized system that wasn't designed for extreme heat, low refrigerant from a slow leak, a dirty condenser coil reducing heat rejection, or ductwork leaks losing cooled air before it reaches living spaces. Start with the filter — it's free to fix and solves the problem more often than you'd think.
What temperature should my AC maintain during a heat wave?
A properly sized and functioning AC system should maintain indoor temperatures 10–15°C below outdoor temperatures. If it's 38°C outside and your home is reaching 30°C indoors, your system is either undersized, malfunctioning, or both. Call Grove Mechanical for a diagnostic — 604-371-4949.
How do I know if my AC is undersized for my home?
Signs of an undersized system: it runs continuously without reaching your set temperature, it struggles on hot days but works fine on mild days, or it was installed without a proper load calculation (Manual J). Grove Mechanical performs load calculations on every new installation to ensure correct sizing.
Is it worth repairing an old AC that can't keep up, or should I replace it?
Current-program note: rebate rules, funding, equipment, application sequence and payment timing change. Do not rely on historic rebate amounts, stacking examples, invoice calculations or eligibility examples in this article. Review the active provider terms and request a free rebate-ready estimate for a current home-specific discussion.