Two outdoor wall units that required a full check before the cold season
In this residential project carried out in Montreal, our AirGreen team intervened for a HVAC service call concerning two outdoor units of Comfort-Aire wall-mounted heat pumps installed high on wall mounts. Upon arrival, several visual elements helped guide our diagnosis: two compact compressors fixed to the wall, refrigerant lines protected by ducts, individual electrical disconnects, metal mounts exposed to vibrations, as well as a typical Montreal backyard environment where leaves, humidity, and temperature variations can quickly affect the performance of a wall system.
The client contacted us because the indoor comfort was no longer as stable as before. One area was cooling less effectively, another seemed to respond slowly to commands, and one of the outdoor units produced a louder noise during startups. In a context where a wall-mounted heat pump is used for both heating and cooling, this type of symptom should not be ignored: a small loss of efficiency in summer can become a much more costly problem when the system is used for heating during cold periods.
Initial assessment of the outdoor installation
The two outdoor units were installed on wall mounts, at a sufficient height to protect the devices from snow accumulation on the ground. This setup is common in Montreal, Laval, Longueuil, on the North Shore and the South Shore, especially when it is necessary to clear ground space or work around outdoor layout constraints. It offers certain advantages but also requires special attention: if the mounts are no longer perfectly rigid, if the anti-vibration pads are worn, or if the refrigerant lines transmit vibrations to the wall, the noise can become more noticeable inside the house.
We first observed the general condition of the units. The outdoor coils showed a normal accumulation of dust, pollen, and light debris, but enough to impair heat exchange. The refrigerant line connections were visible on the side of the units, with aging insulation in some spots. The communication and power wires followed a clean external path, but the age of the installation required a thorough check of connections, terminal blocks, disconnect switches, and mechanical protection.
Symptoms reported by the client
The client described three main problems:
- a gradual drop in performance in one of the zones;
- a vibration noise at startup, especially when the compressor was ramping up;
- an impression that the unit had to run longer to reach the requested temperature.
This type of situation can stem from several causes: clogged outdoor coil, dirty fan, inadequate refrigerant pressure, inaccurate temperature sensor, unstable electronic board, bad electrical contact, partially blocked internal drainage, or vibration transmitted by the wall mount. Our role is never to guess too quickly but to follow a structured diagnostic method.
HVAC diagnosis: electrical, refrigeration, and mechanical inspection
Our technician began by securing the intervention at the outdoor disconnect switches. Each unit being powered separately, we were able to check both systems without mixing the readings. The electrical inspection included checking the terminal blocks, tightening connections, inspecting wire conditions, looking for corrosion in the enclosures, and verifying power stability. On an older wall-mounted heat pump, a simple bad contact can cause intermittent interruptions, communication errors, or irregular startups.
Next, we checked the behavior of the outdoor fans. The blades were spinning, but the buildup of dirt on the grilles and coils reduced the units' ability to release or absorb heat efficiently. In an inverter system, compressor modulation heavily depends on heat exchange conditions. When the outdoor coil is dirty, the unit may run longer, consume more, and seem to lack power.
Refrigerant circuit inspection
An important part of the diagnosis focused on the refrigerant circuit. We observed the fittings, possible oil traces, insulation condition, and the units’ response during operation. A refrigerant leak is not confirmed solely by a feeling of low performance: pressures, temperatures, the temperature difference between return air and supply air, as well as compressor behavior under load must be examined.
In this specific case, the performance drop seemed mainly related to a combination of external dirt buildup, reduced heat transfer, and mechanical vibration, rather than a major compressor failure. This is good news for the client, as a targeted intervention often extends the lifespan of a wall system without immediate replacement.
Technical cleaning of outdoor units
We carried out a careful cleaning of the outdoor coils, respecting the fragility of the fins. The goal was not just to make the devices look cleaner visually, but to restore airflow through the condenser. On wall-mounted heat pumps, a partially clogged coil can cause abnormal operating pressure, overheating, reduced cooling performance, and loss of efficiency in heating mode.
The cleaning included:
- Clearing the outdoor grilles;
- Removal of debris accumulated around the coils;
- Inspection of bent or clogged fins;
- Checking the fan and its bearing;
- Observation of natural drainage around the units;
- Visual inspection of refrigerant lines after cleaning.
This step is particularly important in the residential neighborhoods of Montreal, where trees, leaves, humidity, and seasonal variations accelerate the buildup of deposits on the outdoor units.
Correction of vibrations on wall mount
The second part of the intervention concerned noise. The two units were installed on metal wall mounts. This installation method is acceptable when well executed, but it transmits vibrations more easily than a well-isolated floor base. We therefore inspected the anchor points, bolts, support alignment, and the condition of the anti-vibration pads.
The noise mainly came from mechanical transmission between the outdoor unit, the support, and the wall. Over the years, vibrations can slightly loosen some fasteners or compress the isolators. Our team tightened critical points, adjusted the supports, and checked that the refrigerant lines were not under tension. A line that is too rigid or poorly positioned can amplify noise, especially when the compressor starts.
Checking communication between indoor and outdoor units
Even though the image mainly shows the outdoor units, a complete HVAC repair always requires considering the system as a whole. A wall-mounted heat pump operates through constant communication between the indoor unit, outdoor unit, sensors, electronic boards, and controls. We therefore validated the units’ behavior in cooling mode and heating mode by observing their responses to setpoint changes.
One common mistake is to quickly conclude that the outdoor unit is the cause because it is the most visible part. In reality, an indoor sensor problem, a clogged filter, a dirty turbine, or a partially blocked drain can create similar symptoms. In this case, the indoor units were responding correctly, which reinforced our conclusion: the intervention mainly needed to focus on the outdoor heat exchange and mechanical stability.
Why this type of service call is important before winter
A wall-mounted heat pump used for heating must be able to handle defrost cycles, outdoor humidity, cold winds, and rapid temperature changes. If the coil is dirty or the fan is struggling, the unit may lose efficiency when the customer needs it most. A system that seems just “a little weaker” in the fall can become insufficient during the first cold spells.
That’s why we recommend that homeowners in Montreal, Laval, Longueuil, the North Shore, and the South Shore do not wait for a complete breakdown. A preventive service call can avoid:
- higher electrical consumption;
- longer heating cycles;
- vibration noises in the structure;
- intermittent errors;
- premature compressor wear;
- a loss of comfort in certain rooms.
Common mistakes observed on outdoor wall-mounted heat pumps
On this type of installation, we often encounter the same problems. The first is the lack of cleaning of the outdoor coil. Even if the unit appears to be in good condition, the fins can be clogged by a thin layer of dirt that significantly reduces performance. The second is neglect of the wall mounts. A mount that vibrates slightly today can become a major source of noise after several seasons.
The third issue concerns the insulation of the refrigerant lines. When the outdoor insulation deteriorates, the system loses efficiency and the pipes become more exposed to the elements. Finally, electrical disconnects and outdoor boxes must be inspected regularly, as moisture and freeze-thaw cycles can affect connections.
Result: more stable, quieter, and more efficient operation
After the intervention, the two Comfort-Aire units were restarted and tested under different settings. The operation was more stable, the outdoor ventilation smoother, and the vibration noise at startup had significantly decreased. The client was also informed about points to monitor in upcoming seasons, including the condition of wall mounts, line insulation, and the need for periodic maintenance.
A repair without unnecessary replacement
In this situation, our diagnosis helped avoid a hasty conclusion. The symptoms could have suggested a more serious failure, but the complete analysis showed that a well-targeted technical intervention was enough to improve performance. At AirGreen, we always favor a logical approach: identify the real cause, fix what needs to be fixed, then recommend replacement only when the equipment’s condition justifies it.
Practical advice given to the client
Before leaving the premises, we explained to the client how to recognize signs of a future problem. A wall-mounted heat pump that is working well should produce a stable airflow, maintain the requested temperature without excessively long cycles, and not cause abnormal vibration in the wall. A slight noise at startup can be normal, but a rumble, clicking, or vibration that transmits to the structure warrants an inspection.
We also recommended keeping the area around the units clear. Leaves, branches, shrubs, and snow buildup can harm performance. Even installations at height need monitoring, as debris can accumulate in the grilles and on top of the units.
AirGreen expertise for residential wall systems
This type of service call perfectly illustrates our way of working: a precise visual inspection, a complete electrical check, a refrigerant analysis, attention to vibrations, followed by performance tests. Wall-mounted heat pumps are efficient systems, but they must be maintained and diagnosed rigorously to preserve their performance.
AirGreen regularly services wall-mounted, multi-zone, central, and HVAC accessory systems in Greater Montreal. Whether it’s for a repair, maintenance, noise diagnosis, performance drop, water leak, electrical failure, communication problem, or pre-replacement evaluation, our team brings a practical, hands-on approach tailored to the realities of Quebec homes.
An intervention that extends the system’s lifespan
The final result was clear: better operational stability, noise reduction, improved heat exchange, and a reassured customer before the heating season. An intervention like this is not just about “fixing a device”; it protects the customer’s investment, avoids unnecessary expenses, and maintains a reliable level of comfort in the home.
For owners in Montreal, Laval, Longueuil, the North Shore, and the South Shore, a service call for a Comfort-Aire wall-mounted heat pump or any other wall system can make all the difference between a comfortable season and a breakdown at the worst time. At AirGreen, we focus on precise diagnostics, lasting repairs, and clear communication at every step.