Diagnosing an Electronic Fault on a Residential Rooftop Unit
Recently, our AirGreen team was called out for an emergency response in Plateau-Mont-Royal , Montreal, regarding a Fujitsu wall-mounted heat pump installed on the flat roof of a residential building. The owner reported that the system would not start despite several attempts to restart it. The installation, exposed to the sun and the elements, was powering two MultiZone indoor units.
Inspection and diagnosis: a control board malfunction
Upon our arrival, a complete visual diagnosis revealed several critical clues:
-
The electronic control panel of the outdoor unit showed traces of oxidation and whitish deposit.
-
No outgoing voltage signal to the compressor was detected, although the main power supply was stable.
-
The internal diagnostic screen became unresponsive, confirming a main PCB failure .
Using our professional electronic analyzer and multimeter , we confirmed that:
-
The fuse built into the board was intact.
-
The IPM (Intelligent Power Module) , responsible for controlling the variable frequency compressor, was out of service.
Repair steps completed
Our certified technicians carried out a complete repair, combining rigor and safety:
-
Power off and unplug the system.
We have isolated the unit to avoid any electrical risk during the intervention. -
Disassembly of the Fujitsu control board.
The old card, oxidized and damaged, was carefully removed. -
Cleaning the electronic chamber.
We used a specialized anti-static product to remove all traces of corrosion and moisture. -
Installing a new original Fujitsu PCB.
A calibration was performed to synchronize the new card with the compressor and thermal sensors. -
Reassembly and performance testing.
After powering up, the heat pump restarted immediately. The diagnostic lights confirmed normal operation.
Results: System restored and efficiency restored
Thanks to the rapid replacement of the electronic card , the Fujitsu unit has regained its optimal functioning:
-
Operational inverter compressor ;
-
Indoor/outdoor communication restored ;
-
Stable blown temperature in both areas served;
-
Standardized energy consumption .
The customer, satisfied with the speed of the intervention, also opted for an AirGreen preventive maintenance plan to prevent humidity and thermal variations from damaging the card again.
The Challenges of Rooftop Installations in Montreal
This type of intervention highlights a common issue:
Rooftop units , while practical for space reasons, are exposed to extreme conditions . On the Plateau-Mont-Royal, where flat roofs dominate, temperature variations, acid rain and urban deposits accelerate electronic degradation.
This is why we always recommend:
-
Installation of a ventilated protective shelter for HVAC units located on the roof;
-
An annual inspection before peak seasons (spring/fall);
-
Cleaning the board and connectors every two years to prevent oxidation.
AirGreen expertise: sustainable solutions and rapid interventions
At AirGreen , we operate every day in Montreal, Laval, Longueuil, on the North Shore and the South Shore to diagnose and repair multi-brand HVAC systems , including Fujitsu, Gree, Midea, Sharp, Goodman and Trane .
Our technicians are trained on the latest generation of electronic cards and use manufacturer-certified parts to ensure the durability of each repair.
Conclusion: AirGreen technical mastery and reliability
This case in Plateau-Mont-Royal demonstrates our teams' ability to respond effectively to complex electronic failures of wall-mounted heat pumps.
By replacing the faulty card and restoring system communication, we enabled this customer to regain stable and energy-efficient thermal comfort , even in the middle of summer.
AirGreen — Fujitsu HVAC system repair and maintenance in Montreal, Laval, North Shore and South Shore.
Performance restored, comfort assured.