AC repair

AC Repair in Toronto, the GTA and Hamilton: Fault Finding When the House Won't Cool

Warm air, a frozen coil or an outdoor unit that will not start: we trace the fault first, then explain whether a repair makes sense. Emergency service is subject to availability.

Book an AC repair visit +1 905-407-7353

ScopeCentral air and split-system AC faults
EmergencySubject to availability
Diagnostic feeMay apply; confirmed at booking

What is included
How it works
Details
Ontario notes
Questions
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Central air conditioner condenser on a pad beside a brick house

Serving the GTA and nearby Ontario

Scope

Faults we check on a struggling air conditioner

Thermostat issues: blank display, wrong settings, bad wiring or a failed sensor
Contactor and capacitor problems that stop the compressor or fan from starting
Blower operation: motor, wheel, speed settings and airflow restrictions
Refrigerant symptoms such as ice, weak cooling or hissing, with leak finding before any top-up
Frozen evaporator coils from low airflow, a dirty coil or a refrigerant problem
Dirty condenser coils and blocked airflow around the outdoor unit
Drain blockages and float switch trips that shut the system off or cause leaks
Wiring issues: loose connections, damaged wires, tripped breakers and low-voltage faults

Process

How a repair visit unfolds

Every job starts with a conversation and a look at the equipment. You see the options in plain language before anything is booked.

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1
Symptoms first
We ask what you hear, see and feel. Does the fan run, is there ice, is the floor wet, did it start after a power outage? Small details often narrow the search quickly.
2
Simple causes, then measurements
We start with settings, batteries, breaker, disconnect, filter and drain switch. Then we move to electrical readings, airflow and refrigerant-side observations. This order avoids replacing parts that were never the problem.
3
A plain diagnosis and your options
You hear what failed, what it affects and what the repair involves. If parts are needed, we explain what is available and what has to be ordered. Work proceeds only after you approve it.
4
Repair, test and note anything else
After the repair we run the system through a cooling cycle and recheck the readings. We also tell you about related wear we noticed, so it is not a surprise later.

In pictures

What this work looks like

Outdoor unit opened for repairFan, coil and compressor exposed

Digital manifold gaugesRefrigerant pressures checked

Central AC condenserOutdoor unit installed

Photos from Kelvin Mechanical jobs in the GTA and nearby Ontario.

Good to know

Repair or replace: how we frame the decision

Age and repair history

A capacitor or contactor on an otherwise sound system is a routine repair. Repeated failures, a compressor fault or a leaking coil on an older unit change the picture. We lay out both paths and let you choose.

Low refrigerant means a leak

An air conditioner does not use up refrigerant. If the charge is low, it has leaked somewhere. We look for the leak where practical and discuss repair cost against system age before adding any refrigerant.

Matched parts and availability

Older systems can run into parts and refrigerant availability limits. If the coil and outdoor unit are no longer a good pair, replacement may make more sense. See AC installation for how we plan one.

Emergency calls and diagnostic fees

Emergency service is subject to availability, and we do not promise response times. A diagnostic fee may apply; confirmed at booking. If you smell burning or see water near electrical parts, turn the system off at the breaker first. More on urgent calls is on the emergency heating and cooling page.

Ontario notes

AC repair in Ontario: heat waves, humidity and older systems

Heat wave demand

Air conditioners fail most often during the hottest stretches, because that is when they run hardest. Demand for repairs climbs at the same time, and response options narrow. Emergency service is subject to availability. Early signs such as weak cooling, ice or noise are worth a call before the next heat wave.

Humidity and drain trouble

Ontario's humid summers mean an air conditioner produces a lot of condensate. Algae and sludge can block the drain and trip the float switch, shutting the system off or leaking onto ceilings. A blocked drain is a common reason for no cooling on a humid day.

Cottonwood, seeds and lawn debris

Outdoor coils collect cottonwood fluff, maple seeds, grass clippings and leaves, especially in late spring. A coated coil cools poorly and runs hotter. Keep plants trimmed back and avoid pressure washers. A technician cleans the coil properly and checks the fan and electrical parts at the same time.

Older refrigerants and parts

Systems that use R-22 are harder to service, since that refrigerant has been phased out and supply is limited. Parts for discontinued models can also be limited. These factors, along with repair history, shape the repair or replace decision, and we lay out both paths for you.

Equipment we install and service

Brand names and logos belong to their owners. Availability depends on the product line and region.

Customer reviews

What customers say

Kelvin Mechanical provides great service! Same day service. Zia spent the appropriate time to diagnose the issue with my AC system and repair it, saving me from purchasing a new unit. I highly recommend using Kelvin Mechanical

Rafal S. Google review

The technician from Kelvin was very knowledgable and efficient in diagnosing.the problem! , performing the work and completing the repair of the disabled AC. The cost was fair and reasonable. . Thank you, Claudio Brampton.

Heidi B. Google review

I had an excellent experience with kelvin Mechanical's,Their team was professional, punctual, and incredibly knowledgeable. They quickly diagnosed and fixed my AC issue, ensuring my home was cool and comfortable again. The technician explained everything clearly and provided helpful maintenance tips. Pricing was fair, and the service was top-notch. I highly recommend them for anyone needing reliable HVAC services

Faheem S. Google review

Five-star Google reviews, copied as written with shortened names. Read more reviews

Help centre

Questions about AC Repair

Why is my AC running but blowing warm air?

Common causes include a dirty condenser, a failed capacitor or fan motor, a frozen coil, a low charge from a leak, or a thermostat fault. Each one has a different fix, so we test before replacing anything.

Why is there ice on my indoor coil or refrigerant line?

Ice usually points to low airflow, a very dirty coil or a refrigerant problem. Switch the thermostat to fan only so it can thaw, then call us. Running it while frozen can flood the drain pan and stress the compressor.

My air conditioner is leaking water inside. What now?

Usually the condensate drain is blocked, the pan is cracked, or a frozen coil is thawing. Turn the system off, then we clear and test the drain, check the safety switch and find out why it backed up.

How do I know whether to repair or replace?

We look at age, repair history, parts availability and the condition of the coil and compressor. If replacement looks wiser, we will say so and explain why. A quote follows a site review, and financing options may be available subject to provider approval and terms.

Do you charge to diagnose the problem?

A diagnostic fee may apply; confirmed at booking. It covers the technician time needed to find the fault. Any promotional offer is subject to its own terms and must be confirmed when you book.

Why does my AC turn on and off repeatedly?

Short cycling can come from an oversized system, a dirty filter, a frozen coil, low refrigerant from a leak, a thermostat fault or a failing electrical part. Repeated starting stresses the compressor, so do not ignore it. Replace a dirty filter, then call us. We test the cause before replacing parts.

Why will my air conditioner not turn on at all?

Check the thermostat mode and batteries, the breaker, the outdoor disconnect and the filter. Many systems also have a condensate float switch that cuts power when the drain backs up. If those are fine, a capacitor, contactor or control board could be at fault. Do not open electrical panels yourself.

Why is my air conditioner making a loud noise?

Different sounds point to different faults. Buzzing can mean a failing capacitor or contactor, grinding or squealing often points to motor bearings, and hissing can mean a refrigerant leak. A rattle may be loose panels or debris. Switch the system off if the noise is loud or new, then call us.

Is it okay to add refrigerant to my air conditioner?

Handling refrigerant is regulated work. An air conditioner does not use refrigerant up, so a low charge means a leak somewhere. Topping up without finding the leak only buys time. We look for the leak where practical and discuss repair against system age before adding any refrigerant.

My AC runs but the house stays humid. What is wrong?

Possible causes include an oversized system that cycles too fast, a dirty coil, weak airflow, low refrigerant or a thermostat fan set to on. An air conditioner only dehumidifies while it runs. Ontario's humid summers make this noticeable. We test airflow and coil conditions to find the reason.

My outdoor unit hums but the fan is not spinning. What should I do?

A hum without the fan or compressor starting often means a failed capacitor or a stuck motor. Turn the system off at the thermostat and the breaker to avoid damaging the compressor, and do not push the fan by hand. Call us, and tell us what you hear.

Why is my upstairs hotter than the main floor?

Heat rises, and attic heat, thin insulation and uneven duct balance all make upstairs rooms hotter. The air conditioner may be working but limited by airflow or design. We test supply and return airflow and explain whether the issue is the equipment, the ducts or the building.

Can a storm or power surge damage my air conditioner?

Yes. Lightning, surges and brownouts can damage control boards, capacitors and compressors. After an outage, wait a few minutes before restarting so pressures can settle. If the system does not start or trips the breaker repeatedly, call us. A surge protector can reduce risk, and an electrical professional can advise.

Where we do this work