VARISTOR Explained! Protection, Testing, Diagnosis AC & Refrigeration Electronics Training Class 2

Welcome to Class 2 of our complete Applied Electronics for Refrigeration and Air Conditioning training course. In this video, we focus on one of the most important protection components inside HVAC electronic boards: the varistor.

You will learn step by step how the varistor works, how it protects sensitive electronics in air conditioners, refrigerators, inverter systems, and control boards, and how to properly diagnose failures related to voltage spikes and electrical surges.

🔧 What you will learn in this video:

What a varistor is and why it is essential in HVAC electronics

How a varistor protects electronic boards from power surges

The location of the varistor on AC and refrigeration control boards

How overvoltage damages electronic components

How to identify a damaged varistor

Common symptoms of varistor failure: blown fuses, burned tracks, malfunctioning electronics

Step-by-step testing and troubleshooting procedures

How to measure a varistor with a multimeter

How to replace a faulty varistor correctly

The importance of grounding and proper installation

Real diagnostic techniques used by professional technicians

The varistor is a key protective device used to shield microcontrollers, power supplies, integrated circuits, sensors, relays, fan drivers, and inverter modules from dangerous high-voltage spikes. Without proper protection, electrical surges can cause logic failures, memory loss, erratic relay operation, or permanent damage to power semiconductors.

In this class, we explain in detail how the varistor reacts to high-amplitude short-duration voltage peaks, how it reduces internal resistance in microseconds, and how it diverts excess current away from sensitive components. You will also understand the limits of varistor protection, including nominal voltage, clamping voltage, energy rating in joules, and peak current capacity.

We also analyze real-world failure scenarios such as:

Applying 230V to a 110V varistor

Continuous overvoltage conditions

Thermal stress and overheating

Poor grounding and installation errors

Repeated surge events reducing varistor lifespan

You will learn practical diagnostic steps used by HVAC technicians:

✔ How to safely disconnect and inspect an electronic board
✔ How to visually identify a damaged varistor
✔ How to discharge capacitors safely
✔ How to measure resistance and detect short circuits
✔ How to check nearby components after a surge
✔ How to select the correct replacement varistor

This training is ideal for refrigeration technicians, HVAC professionals, electronics students, maintenance engineers, and anyone who wants to understand electronic board repair in air conditioning and refrigeration systems.

👉 FULL COURSE AVAILABLE!
In the description of this video you will find the direct link to access our complete course on Applied Electronics for Refrigeration and Air Conditioning, with many more practical lessons, diagnostics, and real troubleshooting techniques.

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Видео VARISTOR Explained! Protection, Testing, Diagnosis AC & Refrigeration Electronics Training Class 2 канала CST ChillingSolutionsTraining