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Réparation d’un climatiseur mural Tosot à Candiac
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Repair of a Tosot wall-mounted air conditioner in Candiac

Sudden air conditioning failure in the middle of a heatwave

During the hottest days of summer in Candiac , on Montreal's South Shore , a customer contacted us about a Tosot wall-mounted air conditioner that was no longer blowing cold air despite a red light on the indoor unit. This type of situation is common during periods of high demand—but each case deserves special attention, as the cause can range from a simple faulty sensor to a problem with the electronic board.

At AirGreen , we know that speed and accuracy of diagnosis are essential to minimize inconvenience, so we dispatched one of our certified technicians to your location for a complete service call .

Inspection and diagnosis: a faulty electronic card

Upon arrival, we noticed that the Tosot wall-mounted air conditioner, installed in a bright and well-insulated residential space, was displaying a solid red light—a clear indication of an internal error code . After consulting the Tosot code table, our team identified the error code E1 , signaling a communication failure between the indoor unit and the outdoor condenser .

Here are the steps of our diagnosis:

  1. Check communication wiring (wire 1-2-3) : correct voltage, no visible breaks.

  2. Continuity test between inner and outer terminals : normal results.

  3. Inspection of the indoor unit main board : slight blackening around the main relay confirmed localized overheating .

  4. Compressor check : normal resistance, excluding a major failure on the external side.

So we concluded that there was a faulty electronic board inside, probably due to an electrical surge caused by the recent thunderstorms.

Repair: replacement of the electronic card and recalibration of the system

After confirming the diagnosis with the customer, we proceeded to completely replace the original Tosot electronic card , a part supplied directly by our authorized distribution network.

The intervention took place in four stages:

  1. Main power cut off to ensure safety.

  2. Disassembly of the front cover and careful removal of the defective card.

  3. Installation of the new board and recalibration of the ambient and evaporator temperature sensors.

  4. Complete system test , including synchronization with the outdoor unit and measurement of the R410A refrigerant pressure.

After powering back on, the air conditioner restarted normally. The red light disappeared, replaced by the green stable operation light.

Result: restored comfort and prevention of future breakdowns

Upon completion of the service, the customer immediately felt comfortable , with cool air distributed evenly and quietly. We also took advantage of the visit to thoroughly clean the air filter and recommend installing a surge protector —an essential precaution for sensitive electronics like Tosot wall-mounted air conditioners.

Immediate benefits:

  • Room temperature stabilized in less than 10 minutes.

  • Reduced power consumption thanks to the new calibrated card.

  • Guaranteed optimal operation even in periods of extreme heat.

AirGreen expertise at your service on the South Shore

This type of intervention demonstrates how essential preventive maintenance and professional diagnostics are to extend the life of HVAC systems. At AirGreen , we operate throughout Montreal, Laval, Longueuil, and on the North Shore and South Shore , ensuring precise repairs on all major brands: Tosot, Midea, Fujitsu, Gree, Lennox, Mitsubishi, Trane , and many others.

Our certified technicians are committed to:

  • Quickly diagnose any electrical or electronic fault.

  • Use only original parts and approved tools.

  • Provide a transparent and sustainable service , with personalized advice to avoid recurrences.

At AirGreen, we give your air conditioning systems a new lease of life, for reliable comfort all year round.