Quick answer
Most AC repairs in the GTA cost $150–$800. A capacitor or contactor is $150–$350, a condenser or blower fan motor $300–$700, a control board $400–$800, and a refrigerant leak repair with recharge $300–$800+. Expect a $90–$150 diagnostic fee, credited toward the work. On a unit past 12 years, a repair over half the price of a new system rarely makes sense.
AC repair cost in the GTA depends almost entirely on which part failed. A start capacitor and a compressor both announce themselves as 'my AC won't cool', but one is a $250 fix done in 20 minutes and the other can cost more than the condenser is worth. The price-by-problem breakdown below is what licensed contractors charge across the GTA and Hamilton, so the quote in your hand makes sense in context.
The diagnostic fee
Almost every GTA company charges a service-call or diagnostic fee of $90–$150 to send a licensed technician, test the system and identify the fault. Reputable shops credit that fee toward the repair if you approve the work, so ask before booking. Be wary of 'free' diagnostics — they are usually baked into inflated repair prices, and of very cheap phone quotes that change once someone is standing in the yard.
What to check before you pay for a visit
- The breaker for the condenser and the furnace/air handler — the blower needs power too.
- The outdoor disconnect beside the condenser — pull-out blocks get left out after landscaping or a home inspection.
- The thermostat — set to Cool, setpoint below room temperature, batteries fresh.
- The filter — a starved coil ices, then the AC blows warm air until it thaws.
- The condensate float switch — a full pan or blocked drain shuts many systems off on purpose.
Common AC repairs and what they cost
- Capacitor replacement: $150–$350 — the single most common AC repair; the part swells and fails after years of heat.
- Contactor replacement: $150–$350 — the relay that switches the condenser on; pitted contacts cause no-starts and chattering.
- Condenser or blower fan motor: $300–$700 — parts plus labour, depending on the motor type.
- Refrigerant leak repair and recharge: $300–$800+ — finding and sealing the leak costs more than the refrigerant itself.
- Control board replacement: $400–$800 — common on newer units with electronic boards.
Why refrigerant repairs cost more than parts
A sealed system should never need topping up, so a low charge means a leak, and the technician's time goes into finding it — electronic sniffer, UV dye, a nitrogen pressure test — before any refrigerant goes in. Recharging without the repair pays for the same problem twice, and a low charge is a top cause of an AC freezing up and an AC that will not cool. Vintage matters too: a pre-2010 system still on R-22 is effectively at end of life once it leaks, because that refrigerant is no longer produced or imported, while R-410A remains available for the 2010-and-later generation.
Heat-wave pricing and after-hours fees
- After-hours dispatch runs $150–$300 at many GTA companies, versus $80–$150 during business hours.
- In the first days of a heat wave, queues stretch and some shops prioritize maintenance-plan members.
- ZK Mechanical charges the same rate around the clock, with no weekend or holiday surcharge on emergency calls.
- If the house is habitable, booking the next business-day slot often costs less than an overnight visit elsewhere.
The failures we see most, by housing era
- 2000s builder-grade condensers across Milton, Brampton and Georgetown subdivisions: swollen run capacitors after 8–10 summers, and contactors pitted by cottonwood and dust.
- 2010s systems with TXV metering: stuck expansion valves and failed condenser fan motors, often after a season with a blocked coil.
- 1990s units still running in Mississauga and Scarborough: compressor failures and R-22 leaks, which end in replacement.
- Any age near the QEW or 403: fin corrosion from road salt, which quietly lowers capacity before anything fails outright.
When repair stops making sense
- The unit is 12+ years old and faces a repair over $800 — replacement usually wins on total cost of ownership.
- The compressor or evaporator coil has failed — the most expensive components, and often the first of several failures.
- You have paid for repairs in two or more consecutive summers.
- The system runs R-22 — money spent on it cannot follow you to the next unit.
The working rule: a repair over half the price of a new system on an AC past 10 years old points to replacement. The AC repair vs. replacement guide puts numbers on that decision. If your AC has quit in a heat wave, ZK Mechanical will say plainly whether the part is worth it or whether a replacement is the smarter spend — book a technician or call (647) 801-1252.