A service call in a bright veranda where the wall-mounted heat pump no longer cooled like before
In Boisbriand, our AirGreen team was called for a wall-mounted heat pump repair installed in a room particularly exposed to the sun, surrounded by large windows and overlooking a very bright environment. This type of space is pleasant to live in but places a heavy load on an air conditioning system: solar gains are high, the air heats up quickly, and an aging wall-mounted heat pump can lose efficiency well before a complete breakdown occurs.
The installed unit was a mini-split type wall-mounted heat pump, installed high above the windows. The exact brand and model were no longer clearly visible on the indoor unit’s front, but several signs indicated it was an older system: yellowed casing from years of use, worn air vents, visible buildup in air outlet areas, and noisier operation than recent models. The customer contacted us because the unit was still working but no longer provided the expected comfort on hot days.
This type of service call is common on the North Shore, especially in Boisbriand, Sainte-Thérèse, Rosemère, and Blainville, where many homes have solariums, verandas, glass extensions, or rooms open to the yard. A wall-mounted heat pump can serve this type of space very well, provided its airflow, drainage, heat exchange, and electronic controls are in good condition.
Symptoms observed by the customer
The customer described a progressive situation, not a sudden breakdown. The unit started, the vents opened, the indoor fan blew, but the room remained uncomfortable. The reported symptoms were as follows:
- air blown less cold than before;
- longer operating time to reach the requested temperature;
- more pronounced ventilation noise;
- persistent feeling of humidity in the room;
- slight occasional dripping near the indoor unit;
- dust smell at startup;
- airflow variation depending on the angle of the louvers.
These signs can point to several possible causes: clogged filters, blocked evaporator, dirty indoor fan, partially blocked condensate drain, poorly positioned temperature sensor, refrigerant shortage, weakened electronic board, or tired indoor fan. To avoid a rough repair, our technician performed a complete diagnosis.
A demanding environment for a wall-mounted heat pump
The room had large glazed surfaces on several sides. Even when the unit is properly sized, such a space can put a wall-mounted heat pump under heavy strain. The windows let in a lot of heat, especially in the afternoon, and the indoor unit must produce a constant airflow to mix the air effectively.
The high placement made sense to promote air distribution, but the unit was also near the ceiling, in an area where warm air naturally accumulates. Over the years, if the fan and evaporator become dusty, the actual airflow decreases. The unit may then give the impression of working while being unable to properly handle heat and humidity.
This detail is important: a wall-mounted heat pump can show normal operation on the remote control while having lost a significant part of its actual performance. The problem is not always immediately visible, especially when the outdoor compressor still starts and the indoor unit continues to blow air.
Inspection of the indoor unit
As soon as the front panel was opened, our technician noticed a buildup of dust on the filters, around the evaporator, and in the blow area. The louvers also showed signs of wear, which is common on older units installed in rooms heavily exposed to light.
The filters were sufficiently clogged to reduce the airflow. This was not the only cause of the problem, but it was an obvious factor. When the filters are dirty, air flows less well through the indoor coil. The evaporator becomes colder locally, moisture condenses unevenly, and the unit may start to emit odors or produce a slight drip.
We then inspected the ventilation fan. On several older wall-mounted heat pumps, the fan accumulates a layer of dust stuck to the blades. This buildup changes the air profile and can cause a rougher noise, reduced air jet reach, and less uniform cooling. In this Boisbriand residence, the fan required thorough cleaning.
Condensate drainage check
Since the client had noticed occasional dripping near the unit, the condensate drain was a priority. A wall-mounted heat pump that cools a humid room naturally produces condensation water. This water must flow freely outside or to the designated drainage point.
We tested the flow by pouring a small amount of water into the condensate tray and then observing the drainage speed. The flow was present but too slow. This situation indicated a partial blockage: dust, biofilm, small deposits, or slight sagging in the drain pipe. A partially blocked drain does not always cause an immediate leak. It can cause intermittent overflows, especially when the device runs for a long time on a hot and humid day.
In this case, the comfort issue was due to a combination of factors: reduced airflow, dirty evaporator, dirty fan, and less effective drainage.
Electrical diagnosis and operational check
Before concluding, our technician also checked the accessible electrical components and the device's behavior when cooling was requested. The controls responded correctly. The indoor unit received the remote control commands properly, the fan speeds were functional, and no obvious anomaly pointed to a defective electronic board.
We also checked the return and supply air temperatures after a period of operation. Before cleaning, the temperature difference was insufficient to provide good comfort in this glazed room. After the intervention, the difference improved, and the airflow became more stable again.
No replacement of the compressor, electronic board, or indoor motor was necessary during this service call. The repair mainly involved restoring the normal operating conditions of a device that had accumulated several years of dust and usage stress.
Technical cleaning, drainage correction, and restoring the device's performance
The intervention was carried out with a methodical approach to preserve the existing unit while immediately improving its performance. On an older wall-mounted heat pump, precision is required: plastics can be more fragile, motorized louvers more sensitive, and some parts are not always easily available anymore.
Cleaning the filters and evaporator
We first removed and cleaned the filters. This step seems simple but remains essential. Clogged filters force the indoor fan to work harder and reduce the unit’s ability to extract heat from the room.
The evaporator was then carefully cleaned. The goal was to remove dust and residue buildup without damaging the fins. A clean indoor coil allows air to pass through the exchanger more efficiently, improving cooling and reducing the risk of uneven condensation.
In a glazed room in Boisbriand, where the solar load is high, this improvement is immediately noticeable. The unit no longer has to compensate for internal air restriction, and the temperature drops more gradually and evenly.
Cleaning the indoor turbine
Cleaning the turbine was one of the most important steps. A dirty turbine can significantly reduce airflow, even when the filters seem acceptable. Deposits stuck to the fins create small disturbances, increase noise, and reduce the blowing range.
After cleaning, the airflow was more consistent. The client immediately noticed a difference in the feeling of air circulation. This result is common: many clients think their heat pump is low on refrigerant, while the main problem lies in the indoor section, where the air is actually distributed.
Unblocking the condensate drain
We then fixed the drainage. The condensate pipe was cleared to restore smoother flow. When necessary, this type of intervention can include cleaning the pan, purging the pipe, correcting a low point, or replacing a short section of the drain. In this particular case, a minor correction and cleaning of the drainage passage were sufficient.
Once the drain was cleaned, we performed a flow test again. The water drained properly, with no backflow to the indoor unit. This step is essential to prevent damage to walls, moldings, and surfaces around windows. In a room with a lot of glazing and interior finishing, even a small repeated leak can cause moisture stains or costly repairs.
Final check in cooling mode
After complete cleaning and drainage correction, we restarted the device in cooling mode. The indoor fan ran more freely, noise was reduced, and the blowing temperature was more consistent. The client experienced a more direct fresh air sensation, especially important in a room with large windows.
We also checked the behavior of the shutters. On older devices, the shutters can sometimes move with difficulty or remain in a position that limits distribution. Here, the orientation was adjusted to promote better diffusion in the room, without directing the air jet directly at the occupants.
Parts replaced or repaired
No major parts were replaced. The compressor, ventilation motor, and control board showed no signs requiring immediate replacement. The intervention focused instead on:
- complete filter cleaning;
- cleaning the indoor evaporator;
- cleaning the ventilation turbine;
- clearing the condensate drain;
- checking the drainage pan;
- checking blowing temperatures;
- inspection of the shutters and air distribution;
- basic electrical behavior check.
This type of repair is often the best solution when the device still works but loses efficiency. It extends the system's lifespan, improves comfort, and avoids premature replacement.
Practical advice given to the client
At the end of the service, we explained to the client how to better preserve the performance of their wall-mounted heat pump:
- clean filters more frequently during the cooling season;
- monitor odors at startup;
- do not ignore small water stains near the unit;
- avoid leaving shutters in a closed or too restrictive position;
- have the device inspected before periods of intense heat;
- request professional cleaning when airflow decreases;
- keep windows and blinds well managed during peak sunlight hours.
In rooms with large windows, usage habits matter a lot. Even a heat pump in good condition can be less effective if solar heat enters massively for several hours. A good strategy is to start the device before the room is already overheated, especially on humid days.
Common mistakes to avoid
Many owners wait until the device completely stops working before calling an HVAC repair specialist. However, warning signs are often visible well before the breakdown: louder noise, lower airflow, unusual smell, slower cooling, water accumulation, or a remote control that seems less effective at controlling the temperature.
Another common mistake is to clean only the filters and believe that all maintenance is done. Filters are important, but they do not fully protect the turbine, condensate tray, and evaporator. Over the years, professional cleaning becomes necessary to restore the internal performance of the device.
It is also important to avoid using harsh household cleaning products inside a wall-mounted heat pump. These products can damage plastics, leave strong odors, or affect certain components. HVAC intervention must respect the materials and electrical components of the device.
Expertise useful in Boisbriand and throughout Greater Montreal
This service in Boisbriand clearly illustrates the importance of an accurate diagnosis before recommending a replacement. The device was old but still recoverable. By targeting the real causes of the problem, we were able to restore the comfort of the room without imposing unnecessary expenses on the client.
At AirGreen, we regularly perform wall-mounted heat pump repairs in Montreal, Laval, Longueuil, on the North Shore and the South Shore. Each service call is different: some involve a refrigerant leak, others a stopped compressor, a fan motor, an electronic board, a sensor, a clogged drain, or simply internal buildup that reduces efficiency. The important thing is to make the right diagnosis and propose a solution suited to the age, condition, and environment of the device.
In this case, the solution was clear: clean, clear, check, adjust, and restore the device to performance condition. The client regained a more comfortable room, a quieter device, and better peace of mind before the hot periods.