A wall-mounted compressor installed on a bracket that vibrated, heated up, and no longer met the cooling demand
In Rosemont–La Petite-Patrie, our AirGreen team was called for a Thompson wall-mounted heat pump whose performance had gradually declined. The customer noticed that the indoor unit was still blowing air, but the requested temperature was no longer reached as quickly. On hot days, the system ran for a long time, the outdoor unit became noisier, and indoor comfort varied from room to room.
On site, the outdoor unit was mounted directly on the brick wall, on metal brackets. The installation was neatly positioned, but several details required close inspection: dirt marks on the casing, buildup near the fan grille, direct sun exposure, possible vibrations in the wall anchors, and the outdoor electrical box located under the unit. In an urban neighborhood like Rosemont–La Petite-Patrie, this type of setup is common: yards are sometimes narrow, brick walls amplify certain noises, and wall-mounted outdoor units endure a lot of dust, pollen, reflected heat, and vibrations.
The customer's request was clear: to understand why this wall-mounted heat pump no longer provided the same comfort and to avoid premature replacement if a repair was possible.
Symptoms observed before our intervention
The problem did not present as a total failure. The heat pump would start, the outdoor fan would run, the indoor unit responded to the remote control, but the result was no longer consistent. The customer had noticed several signs:
- Cooling slower than before;
- Prolonged operating cycles;
- Louder noise coming from the outdoor unit;
- Slight vibration noticeable near the wall;
- Indoor air less cold after several minutes of operation;
- Feeling that the system was struggling in the late afternoon;
- Occasional shutdown when the outside heat was more intense.
These symptoms can have several causes: dirty condenser, worn outdoor fan, air restriction, sensor problem, electrical weakness, refrigerant shortage, support vibration, unstable electronic board, or compressor working under strain. A good HVAC repair involves separating possible causes rather than randomly replacing parts.
Inspection of the Thompson outdoor unit
Our technician began with a complete inspection of the outdoor unit. The Thompson casing showed visible dirt traces on the top and around certain areas of the grille. This buildup may seem minor, but on a wall-mounted heat pump, the outdoor condenser must efficiently evacuate heat. If air flows less well through the coil, the machine works longer, consumes more, and loses capacity.
We also checked the wall mounts. An outdoor unit installed on metal brackets must be well leveled, securely anchored, and sufficiently isolated against vibrations. On a brick wall, slight vibration can transmit through the structure and become much more noticeable inside, especially if the unit runs for a long time.
The outdoor electrical box was visually inspected to check the condition of the conduit, fastenings, and accessible connections. No obvious signs of burning or overheating were visible, but functional verification was still necessary to confirm system stability while running.
Diagnosis during actual operation
We started the heat pump in cooling mode and observed the system's full behavior. The outdoor fan started, but the operating noise was louder than expected. The compressor seemed to respond to demand, but the heat rejected by the outdoor unit was not being evacuated as well as it should be on a properly functioning device.
Inside, the temperature difference between the return air and the supply air was present but insufficient for optimal performance. This led us to a combination of problems: reduced heat exchange outside, condenser fouling, vibrations amplified by the wall mount, and prolonged operation caused by an overall loss of efficiency.
Before suspecting a refrigerant leak, we first corrected visible and measurable elements. This is an important step: many wall systems are replaced too quickly when technical cleaning, fixing checks, and electrical verification are sometimes enough to restore stable performance.
Condenser cleaning and airflow restoration
The cleaning of the outdoor condenser was done carefully. Unlike a simple surface wash, technical maintenance aims to clear the coil without damaging the fins. We removed deposits around the grille, cleaned accessible areas of the casing, and improved airflow through the unit.
On a Thompson wall-mounted heat pump, as with most mini-split systems, the outdoor unit plays a crucial role. In air conditioning, it must reject the heat extracted from the house. If the condenser is dirty, operating pressure can increase, the compressor may strain, and indoor efficiency decreases. In heating, a poorly maintained condenser can also reduce the unit's ability to capture outdoor energy.
After cleaning, the fan expelled air more evenly, and the operating noise was already less forced.
A targeted intervention to reduce noise, stabilize the cycle, and extend the system's lifespan
Once the heat exchange was improved, we continued with mechanical and electrical checks. The priority was to confirm that the system could operate reliably after the intervention, without a quick recurrence of the problem.
Checking the outdoor fan
The outdoor fan was at the center of the diagnosis, as the client had reported unusual noise. We observed the rotation, vibrations, and the motor's response while running. The blade was not blocked, but dirt around the grille and increased resistance to airflow contributed to the noise.
We also checked that no part of the casing was vibrating against the wall mount. A slightly loose screw, a poorly supported panel, or a bracket transmitting vibrations can produce disproportionate noise, especially against a brick wall. After adjusting accessible fixing points and checking the leveling, the operation became more stable.
Wall mount and anchor inspection
The Thompson unit was placed on two metal supports. This type of installation is often necessary when floor space is limited or when you want to protect the unit from snow, water, or obstacles around the property. However, a wall mount must be checked over time.
We checked:
- the overall stability of the unit;
- the condition of the brackets;
- contact points with the casing;
- vibrations transmitted to the wall;
- the level of the unit;
- the space under the compressor;
- access to the electrical box;
- the clearance around the ventilation grille.
No major structural problems were found. However, some adjustments helped reduce vibrations felt during operation. This kind of detail greatly changes the client’s experience, especially when the unit is installed near a window or living space.
Electrical check and installation safety
The outdoor electrical box located under the unit was checked to confirm that the power supply was stable and that visible protections were in good condition. When a heat pump starts, slows down, restarts, or seems to lose performance, an electrical cause must always be considered.
In this case, the main problem was not due to a faulty electrical component. The checks rather confirmed that the machine mainly suffered from a lack of external maintenance and amplified mechanical vibration. This conclusion helped avoid unnecessary replacement of costly parts like an electronic board, a fan motor, or a compressor.
Performance test after repair
After cleaning, adjustments, and checks, we restarted the heat pump and monitored its behavior. The cooling cycle was more consistent, the outdoor noise less harsh, and the temperature blown inside improved. The device no longer exhibited the same forced behavior.
The client noticed a significant difference in indoor comfort. The system regained better cooling capacity, and the outdoor unit operated with less vibration. The intervention restored performance without a complete equipment replacement.
Replaced parts and work performed
In this service call in Rosemont–La Petite-Patrie, no major parts had to be replaced. The repair was based on precise diagnosis and targeted work:
- inspection of the Thompson outdoor unit;
- condenser cleaning;
- ventilation grille clearance;
- outdoor fan check;
- vibration control;
- adjustment of accessible fastening points;
- wall mount inspection;
- electrical box inspection;
- air conditioning performance test;
- performance validation after service.
This type of service is often very cost-effective for the owner. A heat pump that seems tired can sometimes regain solid performance when it’s properly cleaned, stabilized, and tested.
Mistakes to avoid with a wall-mounted outdoor unit
This repair illustrates several common mistakes we encounter in Montreal, Laval, Longueuil, on the North Shore and the South Shore.
The first mistake is believing that an outdoor unit mounted on the wall doesn’t need maintenance. Since it’s elevated, it gets fewer leaves than a ground unit, but it still accumulates dust, pollen, urban dirt, and deposits on the casing.
The second mistake is ignoring vibrations. A slight noise at first can become more significant over time. Supports, screws, panels, and contact points should be checked, especially on brick walls.
The third mistake is closing off the space around the unit with objects, plants, storage, or decorative panels. A wall-mounted heat pump needs free air to operate properly. Reducing clearance around the condenser can raise operating temperature and reduce efficiency.
The fourth mistake is constantly lowering the set temperature to compensate for a loss of efficiency. If the system is dirty or vibrating abnormally, a lower setting doesn’t fix anything. It simply forces the machine to run longer.
Why AirGreen prioritizes diagnosis before replacement
A Thompson machine like this can still provide many years of service when the problem is properly addressed. At AirGreen, we take the time to analyze the full context: unit location, condenser condition, fan behavior, vibrations, electrical supply, indoor performance, and symptom history.
In this case, replacement was not the right solution. The right solution was a technical overhaul of the outdoor unit, accompanied by a thorough system check. This approach protects the client’s investment while quickly restoring comfort.
Our teams regularly handle wall-mounted heat pump repairs, noise issues, lack of cooling, ice buildup, water leaks, electrical failures, compressors that won’t start, faulty control boards, or unstable performance. Every service call is different, but our method remains consistent: observe, test, fix, and verify.
Restored comfort in a demanding urban environment
At the end of the service, the Thompson wall-mounted heat pump operated more quietly and efficiently. The client regained a more stable system, capable of meeting cooling demands without constantly seeming to struggle.
In an area like Rosemont–La Petite-Patrie, where wall installations are common and outdoor units are often exposed to heat reflected by brick, urban dust, and space constraints, well-done technical maintenance can make a big difference. This repair improved performance, reduced vibrations, and extended the lifespan of the unit.
For a HVAC service call or a wall-mounted heat pump repair in Rosemont–La Petite-Patrie, Montreal, Laval, Longueuil, on the North Shore or the South Shore, AirGreen offers a professional, precise approach tailored to the reality of each building.