What Causes an AC Unit to Freeze Up in Toronto, OH?
January 29th, 2026
4 min read
Quick Answer
An AC unit freezes up in Toronto most often because of restricted airflow, low refrigerant from a leak, dirty evaporator coils, electrical control problems, or systems running outside their design limits. Higher humidity, proximity to the Ohio River, and moisture exposure—common in Toronto—make freeze-ups more likely. Running the system while it’s frozen almost always causes additional damage.
What To Do Immediately If Your AC Is Frozen
Turn the cooling off right away.
Set the system to OFF, then switch the fan to ON to help melt the ice. Do not restart cooling until the system is completely thawed and the cause is identified. Running a frozen AC can damage the compressor and refrigerant components.
Why You Can Trust This Explanation
I’m Scott Merritt, and I’ve been working in residential HVAC since 1994.
Over the last 30+ years, I’ve diagnosed, repaired, and replaced thousands of residential systems and trained hundreds of technicians across Ohio, including throughout the Upper Ohio Valley.
This article is based on repeat freeze-up patterns we see in Toronto homes, not generic HVAC advice.
Why AC Freeze-Ups Are So Common in Toronto Homes
Toronto’s river proximity creates higher moisture exposure for AC systems.
We commonly see:
- Homes exposed to higher outdoor humidity
- Outdoor units affected by moisture and debris
- Basements with elevated dampness
- Condenser coils impacted by corrosion over time
- Longer run times during humid heat waves
Moisture combined with airflow or refrigerant issues accelerates freeze-up conditions.
The Most Common Causes of an AC Unit Freezing Up
1. Restricted Airflow
This is the most common freeze-up cause we find in Toronto.
Airflow is often restricted by:
- Dirty air filters
- Return ducts affected by basement humidity
- Blocked or undersized returns
- Duct insulation compromised by moisture
Low airflow drops coil temperature below freezing, allowing ice to form.
2. Low Refrigerant From a Leak
Refrigerant does not get used up.
If it’s low, it leaked—often from:
- Corrosion at outdoor coils
- Aging copper line sets
- Moisture-related joint failures
Low refrigerant lowers system pressure, which drops coil temperature and leads to icing.
3. Dirty Evaporator Coil
In damp basements, evaporator coils commonly collect:
- Dust
- Pet hair
- Moisture-bound debris
A dirty coil can’t absorb heat evenly. Cold spots form, moisture freezes, and ice spreads across the coil.
4. Electrical or Control Problems
Moisture exposure shortens the life of electrical components.
Problems can cause:
- Improper blower operation
- Extended run times
- Short cycling followed by long cooling calls
When airflow and cooling output fall out of sync, freeze-ups become likely.
5. System Running Outside Its Design
During humid conditions, systems run longer and harder.
If airflow or refrigerant levels are already marginal, extended runtime pushes coil temperatures below freezing and ice forms quickly.
Ice Location Matters: What You’re Seeing Tells a Story
- Ice on the indoor coil: Usually airflow or refrigerant related
- Ice on refrigerant lines only: Often airflow imbalance or metering issues
- Ice on both the coil and lines: A system-wide imbalance
Ice location helps narrow the cause quickly.
Why Freeze-Ups Usually Keep Coming Back
If an AC freezes once and the underlying cause isn’t corrected, it will almost always freeze again. Thawing the ice addresses the symptom, not the mechanical imbalance. Freeze-ups are one of the most repeat service issues we see along the river corridor.
How Maintenance Prevents Freeze-Ups
Freeze-ups usually develop gradually as:
- Coils accumulate dirt and moisture
- Filters restrict airflow
- Small refrigerant leaks worsen
- Corrosion reduces efficiency
Routine maintenance catches these issues early—before ice forms and damage occurs. Documented yearly maintenance is also required to keep repair and installation guarantees active.
A Real Toronto Home Example
We worked on a Toronto home near the river with a basement air handler that froze repeatedly during humid weather.
The causes included:
- Restricted airflow from damp duct insulation
- Low refrigerant due to coil corrosion
- A dirty evaporator coil
Once airflow and refrigerant issues were corrected together, the freeze-ups stopped.
The Most Common Mistake Homeowners Make Here
Assuming humidity alone is the problem.
Humidity worsens conditions, but freeze-ups almost always involve airflow or refrigerant issues. Restarting the system without diagnosis usually causes repeat icing.
Who This Article Is (And Is Not) For
This is for you if:
- You see ice on the indoor unit or refrigerant lines
- Cooling performance drops during humid weather
- Your home has a basement or moisture exposure
This may not apply if:
- You have a brand-new system with a confirmed factory defect
- You use ductless mini-splits
- Ice forms only on a short exposed line section
What Guarantees Apply If Your AC Needs Repair
Honest Fix Service Trust Guardian (Repairs & Diagnostics)
Freeze-up repairs are protected by our Service Trust Guardian, which includes:
- A 5-year labor warranty on covered repairs
- A 60-day satisfaction guarantee
- No overtime or after-hours charges
- On-time arrival and clean-work commitments
These guarantees remain active with documented yearly maintenance, consistent with manufacturer requirements.
If Freeze-Ups Lead to System Replacement
Honest Fix Lifetime Trust Shield (New Installations)
If replacement becomes the right decision, new systems are protected by our Lifetime Trust Shield, which includes:
- Long-term labor coverage
- A full money-back satisfaction period
- A no-lemon replacement guarantee
- Energy performance accountability
- Apples-to-apples price protection
These protections are written and designed for homeowners in the Upper Ohio Valley.
Other Ohio Valley Communities Where AC Freeze-Ups Are Common
We see similar freeze-up patterns in nearby towns, including:
- Steubenville, OH
- Wintersville, OH
- Mingo Junction, OH
- Brilliant, OH
- Weirton, WV
- Follansbee, WV
- Wellsburg, WV
- New Cumberland, WV
- Colliers, WV
- Hooverson Heights, WV
Frequently Asked Questions
Should I run my AC if it’s frozen?
No. Running it while frozen can cause serious damage.
Is freezing always a refrigerant problem?
No. Restricted airflow is the most common cause we see.
What guarantees do you offer?
Repairs are protected by the Service Trust Guardian.
New installations are protected by the Lifetime Trust Shield.
What To Do Next
An AC freeze-up is a warning sign that airflow, refrigerant, or system balance is off. Addressing it early prevents larger failures.
Call Honest Fix today for a free exact quote.
You can also learn about our guarantees before you decide.
::contentReference[oaicite:0]{index=0}Scott Merritt is a co-founder of Honest Fix Heating, Cooling and Plumbing and brings more than 30 years of experience across HVAC, leadership, and industry education. He serves in a senior leadership and oversight role, providing licensed guidance, reviewing HVAC educational content, and supporting technician training and documentation standards. Prior to co-founding Honest Fix, Scott founded and owned Fire & Ice Heating & Air Conditioning in Columbus, Ohio, which he operated for more than two decades before selling the company in 2025. During that time, he led programs and partnerships including Carrier Factory Authorized Dealer, Trane Comfort Specialist, and Rheem Pro Partner, helping establish high technical and training standards. Scott is the Ohio State HVAC license holder for Honest Fix and provides licensed oversight to help ensure work meets applicable codes and manufacturer requirements. Learn more about Scott’s background and role at Honest Fix by viewing his full leadership bio.
