Repair of a Sanyo wall-mounted heat pump in Lachine

A winter breakdown in the middle of a snowstorm

In the middle of February, a duplex owner in Lachine contacted us about a Sanyo wall-mounted heat pump failure . His system, used primarily for heating, had suddenly shut down during a heavy snowfall. The outdoor unit, mounted on a wall bracket, was partially buried under snow and was no longer releasing hot air.

At AirGreen , we know that wall-mounted heat pumps are particularly sensitive to winter conditions when they are not properly protected. We quickly dispatched a team to diagnose and repair the problem before the indoor temperature dropped further.

Diagnosis: Ice buildup and frosted sensor

As soon as we arrived, we noticed several revealing signs:

• A thick layer of snow and ice covered the condenser and partially blocked the ventilation;

• The discharge hose had slight icing, preventing the refrigerant from circulating properly;

• The outdoor unit would no longer go into defrost mode, a typical sign of a faulty or frosted temperature sensor .

Our technicians carried out the following steps:

1. Complete and safe snow removal from the outdoor unit, without using direct heat to avoid damaging the fins;

2. Measurement of R410A refrigerant pressures to assess system balance;

3. Testing the defrost sensor (thermistor) and the control board relay;

4. Checking compressor current and coil resistance.

The diagnosis was clear: the defrost sensor was frozen and sending inconsistent values ​​to the electronic board, preventing the automatic defrost cycle.

Repair: Sensor replacement and complete maintenance

We replaced the defrost sensor with a genuine Sanyo part compatible with the R410A system. After installation, a complete heating mode test was performed.

Steps to restart:

• Resetting the electronic card to force a manual defrost cycle ;

• Observation of the complete cycle: flow reversal, rise in temperature of the coil, progressive release of ice;

• Checking the drainage of condensates , essential to avoid the reformation of ice;

• Cleaning of the outdoor coil and application of a water-repellent treatment to limit frost adhesion.

Result: The heat pump resumed normal operation, producing warm air at 42°C at the outlet of the indoor unit. The house was warm again in less than an hour.

Results and recommendations for winter

The homeowner was surprised to discover that even a light accumulation of snow can seriously disrupt the operation of a wall-mounted heat pump. We explained to him that automatic defrosting depends on precise sensors and good airflow around the condenser.

Our recommendations for owners of Sanyo and other brand systems:

• Clear snow around the unit after each storm;

• Avoid accumulations on top of the condenser (install a protective shelter if necessary);

• Schedule preventative maintenance in the fall to test sensors before winter;

• Watch for any unusual noises or drops in performance: these often indicate a defrost cycle problem.

AirGreen: experts in maintenance and repair of wall-mounted heat pumps in Montreal

This intervention in Lachine perfectly illustrates our expertise in repairing residential HVAC systems in extreme winter conditions .
At AirGreen, we respond quickly, even during storms, to restore comfort to our customers.

Our technicians are trained to work on all major brands— Sanyo, Fujitsu, Midea, Mitsubishi, Toshiba Carrier, Gree —and ensure repairs meet manufacturer standards.

We serve all of Greater Montreal, Laval, Longueuil, the North Shore and the South Shore , with a constant commitment: to offer fast, safe and sustainable service, whatever the conditions.

AirGreen – Air Conditioning and Heating in Montreal
Your trusted partner for the maintenance, repair and installation of high-performance HVAC systems.
Because comfort, even in winter, should never wait.