When a wall-mounted air conditioner in a condo stops cooling: AirGreen expertise in action
At AirGreen , we regularly work in condominium buildings in downtown Montreal . Recently, our team was called to Ville-Marie for a complete breakdown of a ComfortStar wall-mounted air conditioner , installed on the balcony of a modern apartment. The client had noticed warm air coming out of the indoor head for a few days, accompanied by an abnormal noise coming from the outdoor compressor .
Initial diagnosis: an outdoor unit stuck in safety mode
Upon our arrival, the ComfortStar condenser , installed on an exposed concrete balcony, had stopped starting. The unit appeared to be powered, but the outdoor fan remained stationary and the compressor would not engage . After turning off the power and removing the protective cover, our technician found that the main circuit board was showing signs of overheating—a common occurrence in wall-mounted units exposed to heat and direct sunlight, particularly on enclosed balconies.
We carried out a complete diagnosis:
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Power supply voltage test at the control module input.
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Control of communication signals between indoor and outdoor unit.
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Inspection of the compressor relay , often the cause of random breakdowns.
Result: the external control board was defective, preventing the system from starting up.
Technical intervention: replacement of the electronic card and calibration of the compressor
Our team replaced the original ComfortStar control board with a new part, ordered according to the exact model serial number. After installation, we performed a series of essential steps:
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Compressor calibration and electronic system reset.
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R-410A refrigerant check , confirming normal pressure and no leaks.
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Testing the outdoor fan , the bearing of which showed slight seizure. We applied a technical lubricant to ensure smooth and quiet movement.
Once the power was restored, the compressor restarted with a progressive and stable start , proof of perfectly restored electronic control.
Additional analysis: the effects of prolonged exposure on a balcony
Wall units installed in condos often present specific constraints:
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Reduced ventilation , especially in closed or glazed balconies.
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A buildup of heat around the condenser.
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Accelerated wear of electronic components and fans.
In these cases, our technicians recommend adding a ventilated sun visor or heat shield to prevent the control modules from overheating.
End result: restored performance and comfort regained
After the repair, the ComfortStar wall-mounted air conditioner immediately regained its full performance. The customer noticed efficient cooling of the ambient air within the first few minutes, as well as quieter operation than ever before.
Our technician also set the set temperature and cleaned the interior filter , which is often forgotten by occupants. The customer received a detailed maintenance report , including voltage, pressure and temperature measurements before and after the intervention.
The AirGreen commitment
Every day, at AirGreen , we work on residential and commercial HVAC systems in Montreal , Laval , Longueuil , the North Shore and the South Shore . Our technicians are trained to quickly diagnose and repair any type of breakdown: refrigerant leak, defective electronic board, blocked compressor, noisy fan , and much more.
Our mission is simple: to restore our clients' comfort and peace of mind through professional, transparent, and sustainable interventions.