A service call on the North Shore: loss of performance on a MultiZone installation
In the Sainte-Dorothée district of Laval , a customer contacted us after noticing that one of the two indoor units of his Fujitsu MultiZone heat pump was no longer producing cold, while the other was still operating normally. The installation, consisting of two outdoor compressors installed side by side on floor stands, was showing a performance imbalance typical of MultiZone systems after several seasons of use.
On site, our AirGreen team immediately noticed that one of the compressors remained off , even though the cooling demand was active inside.
Complete and methodical diagnosis
In order to identify the exact cause of the breakdown, we carried out a diagnosis in several stages:
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Indoor/outdoor communication check : 230V/12V signal was present, but outdoor control board was not responding.
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Wiring check : no apparent cuts or oxidation, but slight abnormal voltage at the CNB terminal block.
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Visual inspection of the compressor : no signs of overheating or oil leaks, but presence of dust and moisture around the top cover.
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Coil continuity test : normal result, which ruled out motor failure.
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R-410A refrigerant pressure measurement : very low static pressure (40 psi), confirming a slow leak in the circuit .
After spraying a foam solution on the fittings, we detected the main leak at the compressor outlet flare .
AirGreen intervention: precision and reliability
Once the leak was identified, our technicians followed the complete repair protocol:
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Recovery of residual refrigerant using an approved station.
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Remanufacture of the flare on the liquid line with calibrated tube cutter and clean deburring.
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Fujitsu exact torque tightening according to pipe diameter specifications.
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Nitrogen leak test at 350 psi for 45 minutes.
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Vacuum to -30 inHg to completely dry the circuit.
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Electronically weighed R-410A refrigerant recharge according to the system nameplate.
Once the load was restored, we restarted both outdoor units simultaneously and observed an immediate return of cooling to both indoor areas.
Results obtained: restored comfort and perfect balance
The customer could feel the difference within minutes: the two previously unbalanced zones returned to a uniform temperature. The final readings showed:
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Low pressure: 120 psi
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High pressure: 390 psi
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Indoor blowing temperature: 11°C
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Energy efficiency (EER) stable at 100% of nominal.
This repair not only restored comfort but also preserved the life of the compressor , as a load imbalance on a MultiZone system can quickly cause premature wear.
AirGreen Tips for MultiZone Systems
MultiZone heat pumps, while efficient, require rigorous maintenance to ensure optimal performance. Here are our recommendations:
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Complete annual inspection of refrigerant level and leaks.
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Cleaning the outdoor coils to prevent overheating.
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Verification of electronic communications between units.
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Control of differential pressures between zones to prevent imbalances.
Regular maintenance by an AirGreen certified technician can prevent up to 70% of breakdowns related to leaks or pressure imbalances.
AirGreen expertise: trust at the heart of every intervention
Our mission isn't just to repair: we aim to optimize each HVAC system so it operates at its full potential, summer and winter. This service in Sainte-Dorothée perfectly illustrates the rigor and precision we apply to each intervention—whether it's a Fujitsu, Midea, Gree, Sharp, or Zephyr heat pump .
Our teams travel quickly to Montreal, Laval, Longueuil, the North Shore and the South Shore to diagnose, repair and maintain all types of residential and commercial HVAC systems.
AirGreen — the benchmark for MultiZone heat pump repair in Greater Montreal.