Driver hand tuning air ventilation grille, fresh air is coming out

Car AC Repair Basics

Car Mechanic

Steve Cusson

Steve is a mechanic at Phobia Auto Care. He started his own garage in 2016 and has been there ever since. He works on everything from motorcycles to semis and knows how to keep them in top shape.

We are here to talk about air conditioning today and educate you on why AC is so expensive to repair and diagnose We will also cover the major components of an AC system.

Parts of an AC system


The compressor is what pumps the refrigerant through the whole system.

ECU (Engine control unit)

An ECU controls the air conditioning in modern cars. This means that they’re computer-controlled. If all the sensors aren’t happy, the ECU won’t turn the compressor on.

HVAC Control

The HVAC controls are buttons, dials and/or whatever you use to control the AC. They tell the computer (ECU) to turn on the compressor.


Your condenser is mounted in front of the vehicle, and the cold air rushes through it. Your fans turn on to bring the pressure down, and air rushes through the evaporator (in your dash) which cools the air down.

Accumulator, etc.

There is an accumulator and pressure fittings for hooking up our equipment. Any one of these joints in this closed AC system can leak refrigerant which will cause everything to stop working.

What can go wrong with an AC system

There are many parts to an AC system, which have to work together. It is a sealed system, so if it is low on charge, that means there’s a leak somewhere. There are various tools to detect a leak, including the scan tool, which for almost every new vehicle we have to hook up to diagnose an AC system.

We can have electrical wiring issues, we can have control module issues. There are a lot of different items in the system that can potentially cause a failure if they are not properly maintained. Every function of your vehicle requires an intricate system of many moving parts, working together in cohesion.

Dripping is not a problem

During normal AC operation, especially on a hot day, you’ll notice a puddle of water underneath your vehicle. This is normal. There is a drain in the bottom of the air box that takes all the extra moisture and drains it out, and you’ll see a puddle on the ground.

Fixing an AC isn’t easy

Servicing these AC systems isn’t as easy as going to Canadian Tire and buying an R-134 cap, putting it on and charging it. It’s actually the opposite. That stuff will contaminate your whole system!

How we find leaks

Car AC repair uses a specific machine. You create a vacuum and make sure this system holds a vacuum. If it doesn’t, you have to find the leak. So, you start by hooking a nitrogen bottle up to it and finding where the leak is in this system in your vehicle.

We have a nitrogen tank which we used to charge AC systems so that we don’t waste refrigerant or vent r134 into the atmosphere. Nitrogen is a dry gas and won’t contaminate the system. It is safe to release into the atmosphere. We also have dye, which helps us find pinhole leaks. We have our old trusty 134a machine, and we have our brand new 1 2 3 4 YF machine.

Experienced AC repair team

We have five refrigerant-certified technicians. As you can see, air conditioning is a complex system. It’s not always as easy as just recharging it and going. If you don’t know what you’re doing, you can wreck a component, you could ruin the system, or you can contaminate it. If it’s too hot outside and your AC’s not cooling you down, come down to Phobia and let us cool you down!

If you have your vehicle serviced by somebody who doesn’t know what they’re doing, you can actually overcharge a system, damage components and not have cold air blowing on you.

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