Multizone heating and air conditioning (HVAC) systems are an ideal solution for homes and buildings across Montréal, Laval, Longueuil, the North Shore and South Shore. Thanks to their flexibility, energy performance, and ability to serve multiple independent zones, they’ve become a top choice for many property owners. However, like any mechanical system, they can sometimes fail. At AirGreen, we handle multizone heat pump issues every week and have identified the most frequent problems, their real causes, and most importantly, the best long-term solutions.
Symptoms You Shouldn’t Ignore: When Your Multizone Heat Pump Is Telling You Something
Clients often contact us because their system is acting strangely: unusual noises, inactive indoor units, uneven temperatures between zones, or a complete shutdown of the outdoor unit. These are warning signs. Ignoring them can worsen the situation and lead to much more expensive repairs down the road.
Here, we’ll break down the five most common problems we encounter on multizone heat pumps installed in Greater Montréal, with real-life examples from our fieldwork.
1. One or More Indoor Units Not Heating or Cooling
This is a very common issue, especially during transitional seasons (spring and fall), when heating and cooling needs vary quickly from one zone to another.
Likely causes:
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Dirty or defective sensors.
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Incorrect remote control configuration (conflicting heat/cool modes between zones).
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Stuck electronic valve in the outdoor unit.
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Faulty circuit board (PCB) in the affected unit.
Real case:
This past January in Saint-Bruno-de-Montarville, a client called us about a 36,000 BTU Fujitsu multizone heat pump, where one wall-mounted unit wasn’t heating. After a diagnostic, we found a stuck expansion valve in the outdoor unit and reprogrammed the zones for consistent heating mode. The result: optimal operation without replacing the unit.
2. Outdoor Unit Not Starting or Shutting Off Abruptly
This is a serious red flag, as the outdoor unit is the heart of your multizone system.
Possible causes:
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Low or high refrigerant pressure (R-410A, R-32, or R-454B depending on the model).
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Burned or damaged power board.
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Blocked or defective outdoor fan motor.
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Frost buildup or malfunctioning defrost system.
Real-life case:
In Laval, we recently repaired a Gree Multizone Extrême that kept shutting off every morning. A thermal scan revealed an inefficient defrost cycle due to a defective outdoor sensor. We replaced it, performed a full maintenance, and adjusted the defrost parameters to suit local winter conditions.
3. Unusual Noises or Vibrations from an Indoor Wall Unit
This issue can become very annoying, especially in bedrooms.
Common reasons:
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Poorly secured or weakened wall bracket.
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Unbalanced fan motor.
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Dirt buildup in the blower compartment.
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Loose insulation or internal flap inside the wall unit.
Typical service call:
We recently solved this issue in a condo in Verdun, Montréal, with a 30,000 BTU Tosot multizone heat pump. The client was hearing vibrations from a head unit in the bedroom. We reinstalled the wall plate, rebalanced the fan motor, and did a complete HVAC cleaning, eliminating the noise in a single visit.
4. Error Codes or Flashing Lights
These messages are helpful but often misunderstood by users.
Common error codes:
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E1, E5, P4, U4, depending on the brand (Fujitsu, Gree, Bosch, etc.).
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These can indicate communication failure, a sensor fault, an overheating issue, or a compressor lockout.
What to do:
Take note of the code, power off the unit, and call our experts. We have access to diagnostic manuals for every brand and can interpret the error codes with precision.
5. Major Temperature Differences Between Zones
This problem affects overall comfort in the home and usually points to an imbalance in thermal distribution.
Main causes:
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Poor initial airflow calibration between indoor heads.
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Clogged filters in specific units.
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Refrigerant leak affecting the farthest indoor heads.
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Soundproofing or insulation issues in certain rooms.
Practical example:
In a triplex in Longueuil, we resolved this issue on a 36,000 BTU Bosch BIVA IDS Premium multizone heat pump by recalibrating airflow and performing zone-by-zone thermal balancing, while recommending the client insulate two exposed walls. The improvement was immediate.
Pro Tips to Prevent Breakdowns on a Multizone Heat Pump
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Schedule a full HVAC maintenance at least once a year, especially before winter.
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Clean your indoor unit filters every 4 to 6 weeks.
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Avoid switching frequently between heating and cooling modes during the transition seasons.
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Keep the outdoor unit clear—no snow, no leaves, no obstructions.
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Request a technical inspection if your system is over 5 years old.
Why Choose AirGreen to Service Your Multizone System in Montréal?
At AirGreen, we don’t just repair: we understand the architecture of your installation, its specific needs, and how you use it daily. Our certified technicians service all types of multizone heat pumps—from older models to the latest ones using R-32 or R-454B refrigerants—and we’re fully equipped to handle complex multizone configurations.
With fast response times across Montréal, Laval, Longueuil, the North Shore and South Shore, we offer transparent service, genuine replacement parts, and a clear professional diagnosis on the first visit.
In Summary
Multizone heat pump malfunctions are not uncommon, but most are preventable or easily repairable if addressed early. Whether you’re a homeowner, a property manager, or a business owner in Montréal or surrounding areas, AirGreen is your trusted partner for installation, repair, and HVAC maintenance.