Air Conditioner Recharge

On a hot day there is nothing better than your vehicle's air conditioner system blowing cold air on your face. When this system stops working or becomes weak it can be a problem. Fortunately we have created this guide for you which shows how you can do a simple system recharge and will bring that cold air back for a lot less than you would pay at a repair garage and you don't need to be a mechanic to do it.

You will need an a/c recharge kit which you can get from Amazon for about $35.00 bucks. It's also a good idea to see how the a/c works before you begin.

If repairs have been done, the system will need to be vacuumed down to remove damage causing moisture. If you don't vacuum the system the AC will not be as cold because of the normal air which is trapped inside once you have opened the system up which is explained further down in this article.

This guide should be followed when components like the blower motor (air coming out of the vents) and vent controls are working okay, and the only problem you should be experiencing is the cold air is weak, or not really ice cold like when the system was new or was working to it's full potential.

If your system has stopped working altogether it will need to be checked out which isn't too complicated once you know what to look for. You can get the supplies needed to complete the repair from Amazon or the local parts store.

See Also: Car Air Conditioner Not WorkingPlease follow this guide we have made for you which consists of a video and detailed information which gives you additional tips the video might overlook, appearances may vary, however this process is the same on all vehicles. So let's get started!

Tools and Supplies Needed

  • Air conditioner recharge kit
  • Protective eye wear
  • Work gloves
Before beginning, park the vehicle on a level surface with the engine off, apply the emergency brake with the transmission in park, and wear protective eye wear and gloves.

Step 1

The recharge kit will consist of a can of R134a refrigerant, a control valve which is connected to the can and is used to allow the refrigerant to flow out of the can. A hose with pressure gauge which is used to monitor the pressure in the system and the low side connector that hooks into the vehicle's system low side charge port.

Start the recharge procedure by removing the safety located at the valve base which is indicated by a white or plastic red tag.

Step 2

Locate the low side system service port fitted onto the larger of the two refrigerant lines. This line will be one of two which travels out from evaporator core (near the firewall) and will lead to the rear of the compressor. You may have to look around a little as these locations will vary and may be obscure on some vehicle's.

The low side port will have a smaller fitting than the high side which will be larger so the kit connector valve will not fit onto it which is for safety purposes (Never connect to the high side port when doing a simple recharge).

Step 3

Once the low side port is located, twist the cap counterclockwise to remove, this cap should have an O ring which will seal it to the fitting in the top of the cap. This service fitting is equipped with a hard rubber ball valve seal which the recharge connector pushes downward to open the system port into the charge connector hose.

If when you remove the cap you hear a leak this valve is bad which can be fixed by simply replacing the cap firmly or replacing the valve once the system is empty, this is common.

Step 4

Pull the retainer ring upwards while holding the charge connector, then press down firmly to attach the connector over the service valve on the charge port. The low side fitting will not fit over the high side port to avoid confusion.

When attempting to attach the kit connector you will hear a slight amount of pressure being released for a spit second while the seal is being lodged onto the port flange which is normal.

Step 5

After attaching the recharge kit, the gauge will indicate the static pressure in the system (engine off). If the system is flat with no pressure showing on the gauge there is a leak that must be found and corrected before recharging can begin.

These failures include:

Step 6

With the kit secure and attached to the low side port with low static pressure present, start the engine and allow it to idle and warm up to operating temperature. You don't want to charge the system with the engine is cold because the pressure rises with heat which is the normal operating condition for the system.

Have a helper hold the engine idle up slightly to help warm the engine, this also helps when recharging the system and should be continued until the job is done and you are ready to disconnect the kit.

Step 7

Once the engine is running turn the air conditioner on, adjust the system to the coldest settings including the highest fan speed, this is too work the system to the max which will ensure a full charge. 

Step 8

After the system is turned on wait 30 seconds, the compressor should begin operating will be followed by the pressure dropping on the gauge. Once this happens turn the can upside down and press the plunger valve inward toward the can which will begin the release of the refrigerant into the systems low pressure side tube while the gauge pressure raises, continue this for a few seconds then release the plunger, the gauge will go up signaling the transfer from the can into the system and then back down again once the plunger is released.

Continue this process of press and release until the system has the correct pressure which is indicated on the gauge, do not overfill the system it will not help it be even colder than it already is, in fact if the system is overfilled it will do the opposite and the system will not work as well. If you accidentally overfill the system refrigerant will need to be bled off, see more below.

Step 9

When the system is full the gauge on the kit will show somewhere in the middle on a normal day with an average temperature (about 80° F or 26° C), if the outside air temperature is warmer then usual the gauge should read on the upper side of full but not into the red.

Keep checking the outgoing temperature of the air coming out of the a/c vent, you should feel the coldness coming back to normal, about 52° to 57° F or 11° to 13° C the system is now fully charged.

An additional way to check if the system is fully charged is to use an infrared temperature meter which gives you and correct reading directly on the outgoing low side a/c tube from the evaporator which also indicates a full charge you can also use your hand which will be cold to the touch.

Step 10

Once the maximum coldness has been achieved and with the engine and system still running, release the connector collar to remove the kit. If you shut down the engine and allow the system to neutralize the pressure will rise making it more difficult to disconnect the kit connector.

Now, pull upward on the valve retainer ring on the valve, doing this will release the unit and the service port will close automatically.

Step 11

Once the kit has been removed, reinstall the dust cap to the port do not over tighten the plastic cap.

Step 12

Turn the ignition switch to the off position to shut down the engine, the a/c system will shut down as well. Enjoy the cold air!

A/C vacuum down and re-charge repair guide

When you have made a repair to the air conditioner system of your vehicle and the system has been open moisture will get into the system, its unavoidable. After the unit is back together it must be vacuumed down which can be done with a simple vacuum pump and gauge set which are both available on Amazon for about $119.00 this set can be then used for all future system repairs and while helping family and friends.

As an air conditioner ages the compressor, condenser, evaporator core and hoses can leak or have mechanical failures which warrant replacement. I have created this guide for you so you can do the repairs yourself and save money while having the satisfaction of doing the job yourself.

These systems have a mixture of refrigerant and oil to keep the air conditioning compressor lubricated during operation. Measuring the amount of (peg) oil in the system is difficult because it's spread throughout the system, in other words if there is a major leak and oil is dripping out, the system will need a small amount of oil, unlike a very small leak which releases little to no oil, you must be the judge of this.

Most manufactures recommend the system to be vacuumed down each time you service the system to remove residual moisture which helps the compressor last longer. An a/c system may look a little different from manufacturer to manufacturer but follow the exact same principle.

Check out the video below to see how the job is done and then continue reading below for tips and information you may have missed.

Each system has a specific amount of refrigerant needed to operate correctly and is located in the owners manual or on the system itself, this guide will successfully recharge the system even if this information is not available.

Tools and Supplies Needed

  • Air conditioner recharge gauge set and vacuum pump
  • R134a refrigerant
Before beginning, park the vehicle on a level surface with the engine off, apply the emergency brake with the transmission in park, wear protective eye wear and gloves.

Step 1

A fully charged system contains refrigerant under pressure (70 to 90 psi static - system not running), Allowing the refrigerant 134a to leak into the atmosphere is illegal though not harmful compared to it's predecessor r12, which was slowly bled out of the system by loosening a hose fitting at the gauge set.

This liquid/gas can be recovered if you have a recovery machine which most do not, this machine is mostly found in shops. Connect the gauge set to the low side charge port to check the start of charge before beginning work. If you choose locate a garage to have the refrigerant recovered before work begins. The recycling machine gathers refrigerant along with a small amount of compressor oil which is then is separated into individual tanks.

Step 2

A gauge set is needed to connect to the system on both high and low side pressure ports, and will also be used to vacuum down and recharge the system, inspect the connections to make sure they are tight to avoid leakage. These units must be "air tight" and not have any leaks at hose fittings or valves.

The red colored gauge and connector valve represents the high pressure side of the system, while the blue color represents the low pressure side. The center hose (yellow) is connected to the vacuum pump and then the new refrigerant supply bottle or can, both gauge valves should be closed before attaching them to the system.

Step 3

Once the system is flat with no or little refrigerant present, begin the repair needed by replacing the failed or leaking component, begin by slowly removing the hose which connects to the component. As the final turns on the hose or fitting is undone you will hear a slight release of residual refrigerant which is normal, this means you are good to move forward in the repair such as replacing the compressor of the system.

Complete list of items that now can be replaced
  • High or low pressure hoses
  • Expansion valve or orifice tube
  • Compressor
  • Condenser
  • Evaporator core

Step 4

Now that the failed component has been replaced you are now ready to vacuum down the system, identify the service ports which the low side you should already know. The high side port should be on the line between the condenser and the expansion valve or orifice tube, remove the service port cap.

Step 5

While pulling the connector retainer ring upwards, press the valve over the service port, repeat this process for both ports. High and low side fittings will only work on their respective ports only due to size constraints this is to avoid confusion. Once secured, tighten the valve which activates the internal plunger that opens the service port valve to the refrigerant lines.

Step 6

Now observe both high and low side gauges with the valves closed, there should be little to no pressure in the system.

Step 7

Next, connect the center hose from the gauge set (yellow) to the vacuum pump, after reading the operation instructions for the pump, turn the pump on, this step is used to remove any moisture and static air from inside the system.

Step 8

Slowly open the low side gauge valve, the pump will now start pulling vacuum throughout the system as the gauge needle slowly moves downward.

Step 9

Once the vacuum pump has been on for 30 minutes, close the low side valve, the system should hold at 28-29 inches. Turn the vacuum pump off, at this point if the system loses vacuum on the gauge there is a leak and must be rechecked. These system leaks ill probably be a faulty O ring seal installed during the installation or a loose hose on the valve set. If the system holds vacuum for 15 minuets proceed to the next step.

Step 10

Next, disconnect the yellow hose from the vacuum pump and attach it to a new R134a refrigerant source which could be a keg (shown) or individual cans which are both available at the Amazon or the local parts store.

Step 11

After the hose is connected to the refrigerant source open the valve on the keg and turn the it over to allow the liquid chemical to be present at the valve which helps charge the system more rapidly. If you are using individual cans connect them to the hose and turn them over as well.

Step 12

While the gauge valves are closed and once the refrigerant source has been opened, the gauges will respond with an equal readings on both high and low side letting you know the refrigerant is present and ready to be installed. This is static pressure which will vary depending on outside temperature, the warmer it is the higher the reading will be which is normal.

Reference the image below to see how the refrigerant will flow once the low side gauge is opened.

Step 13

Next, start the engine and turn the system to the highest settings of coldness including the fan speed. This will help work the system to it's fullest which will help charge the system completely.

Step 14

Once the engine is running and the system is switched on slowly open the low side (blue) valve (never open the valve completely) until the refrigerant starts to flow to the compressor which will turn the system on via the pressure sensor. When this happens low the gauge pressure will start to drop and will cycle on and off as the system low side pressure raises and then lowers, the high side pressure will steadily start to rise. It helps to use a garden hose and spray water over the condenser at the front of the vehicle to help keep the system cool which completes the charge.

Step 15

Continue adding R134a until the gauges start to look like this and the system stops cycling. If both gauges are too high the system is overcharged or the cooling fan is not working. If high side pressure runs way up quickly, (300+) and the low side goes into a vacuum, the system has blockage such as a plugged expansion or orifice tube. If the compressor engages, and neither gauge pressures move (stay the same) the compressor has failed and needs replacement.

Step 16

As these pressures rise monitor the temperature of outgoing line of the evaporator and air vents in the passenger compartment, both should be cold to the touch signaling the system is full. Do not install more refrigerant thinking it will make the system colder, if fact it will do the opposite and make the system warmer as it's unable to achieve the pressure drop needed inside the evaporator.

Step 17

Once the system is performing properly and producing cold air close the low side gauge valve. If the system is not working basic troubleshooting is needed.

Step 18

After you have completed the charge, turn the ignition switch off and the system will shut down along with the engine.

Step 19

With the engine off, turn the high side connector counterclockwise to close the internal valve and release the plunger effectively disconnecting from the service port, repeat this procedure for both high and low side valves.

Step 20

Firmly grasp the valve retainer and pull up, this will release the connector from the service port. You will get a slight pressure lease sound when this is done which is normal, repeat this procedure for both valves.

Step 21

Once both valves have been removed, reinstall the dust cap for each service port. Once the job is complete, close the refrigerant supply valve and store the gauge set properly for the next repair. Enjoy the cold air!

If you need more information about this subject please visit our forum where thousands of questions about air conditioners have been previously answered by our mechanics.

Article first published