10 months ago

When and How to Recharge Your Car AC – A Detailed DIY Guide

Have you ever wondered how your car’s interior stays at the temperature you want it to? Like, the outside is above 110 degrees and the interior is at 75 degrees? 

Has the thought ever crossed your mind that the air conditioner of your car is housed in the engine compartment? A place that can easily be above 250 degrees? 

Let’s see how the AC chills your car. You can learn how to recharge car AC  once you know how it works.

How Does a Car AC Work? 

Evaporation causes coolness! Remember that from 5th-grade physics? That’s the principle on which the AC of a car, or any other AC, works. 

The air conditioning system of your car has five components that make it work: 

  • Compressor
  • Condenser
  • Expansion valve
  • Evaporator
  • Propellent

The compressor of a car’s AC is powered by a belt. The moment you turn on the AC, an electric clutch in the pulley of the compressor is activated and starts driving the pump. 

The compressor is a pump that compresses the gas to liquefy it and sends it to the evaporator through the expansion valve. As the gas passes through the expansion valve, it evaporates. This is the step that causes the gas to cool down. 

In the evaporator, the heat from the air in the passenger compartment is absorbed and the gas flows back to the compressor through the condenser.

The condenser cools the gas down and then the compressor liquifies and the process goes on.  

That’s enough physics for a blog post –  so let’s now see when and how to charge a car air conditioner. 

Signs Indicating the Need For AC Recharge

When your AC needs recharging and is low on gas, you can tell from one or all of the following signs.

1. The AC Does Not Cool The Car 

The biggest indication of a car’s AC not working correctly is that it does not do what it is supposed to, i.e., it does not cool the car down. If you are not getting cooling even at the lowest temperature settings of the car’s climate control, your AC needs recharging. 

However, a choked cabin air filter can also be a cause of lost cooling. Before you go on to charge the AC, it would be a good idea to check the cabin filter.

2. The AC Clutch Does Not Engage 

The AC clutch we explained above has a safety feature built-in. It does not engage when the refrigerant pressure in the AC pipes is below the safe level. This is because running the AC with low refrigerant pressure can destroy the compressor. 

To check for this, open the hood of your car, start the car, and ask someone to turn the AC on. If you notice a change in the sound of the engine and hear a click, the clutch is engaging. If you don’t, the clutch is not working. In that case, you need to charge your AC.

The clutch can sometimes not engage due to a faulty refrigerant pressure sensor. To check for this, locate the sensor on the refrigerant line. Take the wires off of it and close the circuit. If the AC starts cooling, it does not need a recharge.

However, if the AC does not cause cooling even by doing this, do not run it for more than a minute as the compressor can be destroyed when run without gas.

3. Signs of Leakage 

If you see oil or grease oozing out of the compressor housing or the joints of the coolant pipes, it indicates that there’s a leak in the AC system somewhere and the coolant needs to be recharged. 

Fix the Leak Before you Recharge the AC

As most of the time AC systems lose their pressure due to leakage, you need to fix the leak before recharging the AC. Here’s how you can find a leak.

Things Needed

  • AC leak detection kit
  • UV light

The AC leak detection kit has gas with a UV dye added to it. Here’s how you can use it to detect leaks.

  • Locate the low-pressure refrigerant line and attach the can with the UV dye gas to it.
  • Turn the engine on and activate the AC. 
  • Pull the trigger on the can to transfer some of the dye to the AC system. 
  • Move the car to a dark place and shine the UV light on all the components and pipes of the AC system.
  • If anything glows in the dark, it indicates that there’s a leak.
  • You need to repair/replace any such part before recharging the AC.

How To Charge Your Car Air Conditioner 

Now that you know how to tell when your car’s AC system needs a recharge, it is time to learn how to charge a car’s AC refrigerant. 

The steps to do it are simple, but as you are dealing with hazardous material, the refrigerant, you need to be careful. 

Things Required for Charging Car AC Refrigerant 

You’ll need the following things to recharge the refrigerant in your car’s AC: 

  • An AC dispenser with trigger and low side gauge
  • A thermometer
  • Refrigerant specific to your car’s AC system
  • Safety gloves and goggles

Step 1: Find Out if the Compressor Clutch is Engaging

The first step in automobile freon recharge is to determine if the AC compressor is actually turning or not. To do this, turn on the AC and see if the compressor pulley turns or not. 

If the AC compressor is not working: 

  • It can be due to extremely low refrigerant pressure in the AC system. 
  • The electrical system that engages the AC clutch might have failed.
  • The compressor itself might have failed.

If that is the case, it is suggested to not undertake this as a DIY repair and go to the professionals. 

Step 2: Check the Refrigerant Pressure in the AC System of Your Car 

Next, you need to check the refrigerant pressure in your car’s AC to be sure that the loss of cooling is caused by a decrease in gas pressure. Here is how to do it: 

  • Locate a grey or black plastic cap attached to an aluminum pipe in the engine bay. 
  • If you cannot find it, trace the large coolant line coming out of the passenger compartment and into the engine bay and you’ll find the cap on it.
  • Remove the cap and attach the pressure gauge to the service port beneath it to check the pressure.
  • With the AC turned on and on the lowest temperature settings, make sure that the AC compressor clutch is engaged.
  • The pressure of the refrigerant in the system needs to be at least 35psi. Anything below that indicates that your AC needs recharging.

Step 3: Attach the Refrigerant Can 

With the AC still running, thread the refrigerant can to the port on the service hose. Let the engine run and the compressor turn. 

  • Press the trigger on the refrigerant can for 10 to 20 seconds and let the gas go into the system. 
  • Keep monitoring the pressure to make sure you do not overcharge the system.
  • Do not charge the pressure to more than 45psi.

Step 4: Monitor the Temperature

Once the refrigerant pressure has been maintained, you need to make sure that the AC is actually doing its job. Leave the AC running and go inside. 

  • Check the temperature of the air coming out of the AC vents. 
  • The air needs to be at 28 degrees if the AC is doing its job.

Important Note 

The air conditioning system on a car is a highly specialized piece of machinery. The slightest error in recharging the AC can result in major problems.

The refrigerant used in AC systems is also extremely harmful to the atmosphere. 

The best practice is to leave AC repair to the professionals.

Frequently Asked Questions

How do I recharge the car AC after compressor replacement?

Locate the low-pressure refrigerant line, attach the refrigerant can to it, run the AC, and pull the trigger on the can to recharge the car AC after compressor recharge.

How often does a car AC need to be recharged?

There is no mileage limit for recharging a car’s AC. You only need to recharge the AC if the system stops cooling or if there are visible signs of refrigerant leakage from the AC system.

How long does it take to recharge an AC in the car?

It depends on the person performing the repair. Professionals can do it in less than an hour. As a DIY project, it can take 2 hours. However, it must be noted that the main time-consuming thing is locating and fixing a leak that causes the AC system to lose pressure. The actual recharging process is not that long.

How do you know when to recharge the car AC?

The biggest sign of this is the loss of cooling. If the car’s AC is not cooling, you need to recharge the system. Recharging is also needed after a compressor replacement.

What is needed for automobile freon recharging?

You need a can of gas, service lines, a pressure gauge, and a thermometer to recharge the coolant in a car AC.

DISCLAIMER: This article is to give you an idea of how the AC system can be repaired. It has been mentioned above and is being stressed again that the refrigerant is a highly dangerous gas and you need to deal with it with care. The slightest error in this procedure can lead to deadly consequences. Unless you don’t really know what you are doing, it is better to leave this repair to the professionals.

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