A suspended outdoor unit that no longer blows: a quick and precise diagnosis
At AirGreen , we frequently receive calls about LG wall-mounted heat pump breakdowns in North Shore homes, especially during the changing seasons. This is exactly what happened in Sainte-Thérèse , when a customer contacted us because their LG wall-mounted heat pump had stopped blowing hot air. The outdoor unit, mounted on a high wall bracket, appeared intact—but behind this apparent normality lurked a very specific problem.
The initial inspection: safety and observation
Upon our arrival, our team conducted a safety check before handling the unit. The condenser, securely attached to the brick wall, was more than two meters above the ground—a common configuration in residential areas of Sainte-Thérèse, where homeowners prefer to avoid winter snow accumulations around the equipment.
We observed:
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A complete failure of the external fan to start.
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No compressor noise.
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The indoor unit was working, but the air remained lukewarm.
These clues pointed us towards a communication failure between the electronic cards .
Step 1: In-depth electrical diagnosis
Using our multimeter and a continuity tester, we checked the voltage between terminals 1, 2, and 3 of the communication cable connecting the two units. The result: no stable voltage between 2 and 3, indicating that the LG outdoor unit's main board was no longer receiving the signal correctly.
We also inspected the exposed connection box . Slight corrosion on the internal terminals likely explained the signal interruption.
Step 2: Disassembly, Cleaning and Replacement
After turning off the power at the circuit breaker, we have:
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Unplugged the communication cable.
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Thoroughly cleaned the terminals using a dielectric product .
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Replaced the external electronic board, original LG part, ordered according to the serial number of the unit.
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Reset the system via the manufacturer's recommended sequence (5 minute shutdown, full reboot).
Step 3: Performance Testing and Calibration
Once the system was powered back up, the heat pump immediately resumed its normal cycle:
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The outdoor fan started smoothly.
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The inverter compressor gradually stabilized its speed.
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The indoor blowing temperature rose by 8°C in less than 10 minutes.
Pressure and temperature readings indicated optimal operation of the refrigeration circuit. We then securely secured the cables in waterproof conduits to prevent future moisture infiltration.
The particularity of high wall heat pumps
Installing a raised outdoor unit, like here in Sainte-Thérèse, has real advantages:
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Protection against snow and ice.
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Better air circulation around the condenser.
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Easier access for maintenance.
However, this configuration requires periodic inspection of electrical connections exposed to wind, rain, and temperature fluctuations. A simple water infiltration into a poorly sealed enclosure can cause a major electronic failure.
Maintenance Tips for LG Heat Pump Owners
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Clean the internal filter every two months.
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Clear the outdoor unit of any obstructions (branches, leaves, ice).
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Have electrical connections inspected once a year.
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Watch for unusual noises : A fan or compressor that won't start requires prompt attention.
These simple actions extend the life of the system and reduce the risk of costly breakdowns.
Result: comfort restored, reliability assured
After our intervention, the LG wall-mounted heat pump returned to full performance. The Sainte-Thérèse customer reported a significant improvement in indoor comfort and a rapid return to heating, even on cool March evenings.
With our HVAC repair expertise , we not only restored communication between the units, but also ensured long-term system reliability through original components and careful calibration.
AirGreen – Specialists in wall-mounted heat pump repair in Montreal, Laval, Longueuil, North Shore and South Shore.