How to Add Freon to Cars

by Contributing Writer; Updated June 12, 2017

When your car's air conditioner doesn't seem to be blowing cold air anymore, you may need to add Freon to the air conditioning system. Mechanics can charge hundreds of dollars to do this, but you can do it for much less if you know how. Learn how to add Freon to a car air conditioner by following these steps.

Under The Hood:

 How to Add Freon to a Dodge RAM 2500

Raise the hood of the car. Bolted to the back of the air conditioner compressor are two hoses. One hose is larger and goes to the firewall at the back of the engine bay. This location on the firewall is where refrigerant enters and leaves the truck cabin. The suction hose (the large hose) pulls the refrigerant from inside the truck cab where it has circulated and extracted the heat inside the truck. The smaller hose leaving the back of the compressor is routed to the front of the truck. This is the discharge hose that carries the hot refrigerant to the condenser that is located in front of the radiator where it dissipates the heat that is captured in the R-134A refrigerant.

Remove the service port caps that are located either on the hoses or compressor, depending on the year of the Ram 2500. These ports are labeled if they are on the compressor by the letters S and D. S stands for suction and D for discharge. Close the service valves on the A/C service gauges and install the hose that is connected to the blue gauge onto the S port. Connect the hose that goes to the red gauge onto the D port. Install a can of freon onto the can tap that is connected to the center hose of the manifold gauge.

Start the truck, turn on the A/C and read the A/C service gauges. It is not necessary to open the gauge valves. If the A/C gauge readings are zero, the 134-A refrigerant has all leaked out and there is no refrigerant pressure inside of the A/C system to read. Repairs are needed before recharging, because all of the refrigerant would leak out again.

Add a can of refrigerant if the A/C gauge pressures are rising and falling as the compressor is turning on and off. This means there is not enough refrigerant to keep the compressor electrical system energized, so pierce the can of refrigerant with the can tap that is part of the A/C gauge service set, and slowly open the A/C gauge blue valve allowing refrigerant to flow from the can into the A/C unit.

Turn the blue valve off and allow the system to stabilize. The pressure readings need to be around 35-psi and 250-psi, but there are variables involved. If the day is very hot and humid, the low pressure (blue gauge) may read upwards of 40-psi or more, and the high pressure (red gauge) could reach 275-psi. Add refrigerant until the desired readings are achieved and shut off the valves, then remove the hoses. Replace the service port caps.

Items you will need

  • A/C manifold gauges

 How to Add Freon to a 97 1500

Raise the hood on the Dodge Ram 1500. Make sure the engine is completely cool, to avoid burns. Open the air conditioning gauge kit. This kit contains an air conditioner gauge to measure the pressure in the compressor, a can of R-134A freon, and a can cap to open the freon.

Locate the air conditioner compressor in the front of the engine. The compressor is identified as being between eight and twelve inches long with aluminum coloring. It will have a belt and two black hoses, one larger than the other.

Remove the two port caps. There are two locations to check for these caps, based upon the year of the 1500. The caps are for servicing the truck and can be located on either hose or on the compressor. One cap will be labeled "S" for suction and the another will labeled "D" for discharge.

Close the service ports, or valves, on the air conditioner servicing gauges. The air conditioning servicing gauges connect to the air compressor to measure the pressure and freon in the 1500. It will have a blue gauge for low pressure and a red gauge for high pressure, each with distending hoses. There is a center hose for adding the freon. Connect the blue gauge hose to the "S" port. Connect the red gauge hose to the "D" port.

Attach the can of freon to the center hose on the air conditioner gauge. Crank the Dodge Ram 1500 and cut the air conditioner on high. Return to the engine and read the gages to determine the pressure within the air conditioning compressor. If the gauge reads zero, there is not any freon in the 1500, and the air conditioner will need servicing before adding additional freon. If the pressure level is high, the truck does not need any additional freon. If the pressure is moving back and forth from low to high or vice versa, freon should be added.

Pierce the can of freon with the can cap, and slowly open the blue valve on the air conditioning gauge to release the freon into the compressor.

Close the blue valve and wait ten minutes to obtain an accurate pressure reading. The freon will slowly pour into the compressor. A reading of 35-psi to 275-psi is within normal range. Once the desired pressure is reached, shut off the valves.

Remove the hoses and put the port caps back on to the compressor.

Items you will need

  • Air conditioner gauge kit

 How to Add Freon to a 1999 Pontiac Grand Am

Drive the vehicle until the engine reaches operating temperature. Place the transmission in "Park" and allow the engine to idle.

Apply the parking brake and open the hood. Turn the air conditioning selector knob to “Max A/C” and place the blower fan on its highest setting.

Locate the blue low-pressure port cap and remove it (you will find it attached to the low-pressure port fitting, on top of the large diameter aluminum refrigerant line located to the left of the air conditioning compressor).

Connect one end of the in-line refrigerant pressure gauge to the low pressure port. Connect the other end to the refrigerant canister.

Record the reading on the pressure gauge.

Rotate the refrigerant canister until it is upside-down. Gradually tighten the refrigerant release valve until it punctures the seal on the R-134a refrigerant canister. Monitor the pressure gauge. Loosen the release valve to stop the flow of refrigerant once the pressure gauge displays a reading of 45 psi.

Remove the pressure gauge and replace the low-pressure port cap. Check the temperature of the air inside the vehicle to make sure it is sufficiently cool.

Items you will need

  • In-line refrigerant pressure gauge

  • R-134a refrigerant canister

 How to Add Freon to a Maxima

Raise the hood of the vehicle. The air-conditioning system will have two service ports: a high side and a low side. The low side service port will have a blue cap on it. Both ports are located near the top of the engine compartment and should be visible.

Remove the blue cap from the low side service port. Inside is a schrader valve, which looks similar to a tire valve that you use to inflate tires. The cap is threaded onto the line and must be unscrewed.

Place the side of the low-pressure hose with the valve over the top of a can of refrigerant. Lock it in using the handle or screws that come with the hose. Don't turn the valve yet. Thread the other end of the hose over the low-pressure service port, tightening it by hand.

Start the engine of the vehicle and turn the air conditioning to high. Turn the valve on the low-pressure hose clockwise as far as it will go to pierce the top of the can. Turn it counterclockwise to open the valve and allow the refrigerant to flow into the system. Shake the can gently as you do this and throughout the charging process. In about one minute, the can will be empty.

Close the valve on the low-pressure hose by turning it clockwise. Remove the low-pressure hose from the schrader valve and replace the cap. Check the operation of the air-conditioning system after a few minutes.

Items you will need

  • One 8-oz.can of refrigerant

  • Low pressure, air-conditioning charging hose.

 How to Add Freon to a 1990 Honda Accord

Check the AC pressure readings using an Air Conditioning gauge. The AC gauge set has colored hoses for connecting to the vehicle's compressor, which is on the side of the engine (left or right) and has two hoses connected to it. The AC gauge's blue hose fits on one hose (low side) fitting, and the red hose fits on the other hose (high side) fitting. The 1990 Honda Accord has screw-on fittings. Make the connections first, then start the engine and turn on the car's AC. Only add Freon if the AC pressure is low.

Alternatively, check the pressure when you connect the can of Freon to the vehicle.

Connect the hose on the can of Freon to the port on the larger of the two lines on the Accord's compressor. Turn on the Accord and run the air conditioning on the highest setting. Shake the Freon container vigorously. If the gauge is reading in the blue area, there is no need to add Freon. If it is in the green area, you need Freon.

Squeeze the trigger on the can of Freon when the compressor kicks on, to add Freon to the Accord's AC system. Release the trigger when the compressor kicks off and check the gauge on the can of Freon. Once the gauge reads in the blue area, you do not need to add any more Freon.

Turn the engine off and take the hose off the compressor's tubing. Check the operation of the Accord's air conditioning.

Items you will need

  • Freon

  • AC gauge set

 How to Add Freon to a 1994 Toyota Camry

Close the valves on the gauge set by turning them clockwise until they stop. Attach the A/C gauge set to the service ports on the A/C lines. Both the high-pressure port and the low-pressure port are located on the A/C lines, near the passenger side of the firewall. Attach the blue hose from the gauge set to the low-pressure port. The lo- pressure line is the larger of the two lines. Attach the red hose to the high-pressure port. The high-pressure line is the smaller of the two.

Set the controls on the dash to max A/C and medium blower speed. Push the button to turn the A/C on and start the engine. Allow the engine to run for a few minutes, then read the pressures displayed on the gauges. A fully charged A/C system will have a low-pressure reading of 35 to 40 psi, and a high-pressure reading of 250 to 350 psi.

Attach the can tap to the yellow service hose on the gauge set and insert a can of refrigerant into the tap. Close the thumbscrew on the tap, and then open it again, to open the can of refrigerant. Open the blue service valve, by turning it counterclockwise a few turns, to add refrigerant to the system. Close the valves when the can feels about half empty and recheck the gauge readings. Add additional refrigerant to the Camry if the readings are still low. Stop when the gauge readings are in the normal range.

Close the service valve on the gauge set and turn the engine off. Allow the gauge readings to drop, and even out, before disconnecting the gauge set. This will prevent damage to the service ports in your Camry.

Items you will need

  • A/C gauge set

  • Can tap

  • Refrigerant

 How to Add Freon to a Mazda 626

Pop the hood of the Mazda and locate the "Low" pressure air conditioner valve on the rear firewall of the engine compartment. The Low pressure valve is marked with an "L" while the High pressure valve has an "H" on it.

Use the crescent wrench to remove the Low pressure valve cover and make sure the valve is free of dust. Screw the transfer hose from the R134 refill kit onto the valve and then use the calibration knob on the pressure dial to select the outside temperature of the ambient air.

Screw the other end of the transfer line onto the can of R134 and then tighten down the "puncture valve" on the side of the transfer line to puncture the can and release freon into the transfer line.

Open the valve on the transfer line after you start the car's engine and turn on the air conditioner. When the valve on the transfer line indicates that the system is full, turn the car and air conditioner off, disconnect the transfer line from the low pressure valve, and properly discard of the freon kit.

Items you will need

  • Freon (R134) recharge kit Crescent wrench

 How to Add Freon to a 1995 Buick Regal

Locate the air conditioning compressor, next to the battery.

Back-off the valve handle that comes in the kit and screw it into the refrigerant kit until the rubber O-ring is inside the threaded portion.

Remove the dust cap from the "low-side" charging connection.

Attach the quick fitting on the kit hose to the charging connection.

Start the engine and let it run for about 10 minutes with the air conditioner on taking car that the hoses aren't near the engine fan and other moving parts.

Make sure the compressor is on.

Turn on the valve handle until you hear the refrigerant release.

Add refrigerant until the accumulator surface and the evaporator inlet pipe are about the same temperature to touch.

Place thermometer on the air conditioning vent in the cab. The temperature should read 40 degrees if system is fully charged.

Close the valve on the canister and store any excess.

Put dust cover back on the "low-side" charging connection.

Items you will need

  • R-134a charging kit

  • Thermometer

 How to Add Freon to a Buick Roadmaster

Attach the blue and red hoses on the air conditioning gauge set to the Buick's service ports located on the air conditioning lines in the engine compartment. On the Roadmaster, attach the blue hose to the low-pressure service port located on the A/C accumulator between the power steering fluid reservoir and the firewall. Attach the red hose to the high-pressure service port located on the A/C line near the passenger side of the radiator.

Screw the yellow hose from the gauge set to the can tap. Screw a can of R-134A refrigerant to the can tap. Check to be sure both valves located on the gauge set are closed. Open the can of refrigerant by twisting the thumbscrew on the can tap counterclockwise until it stops. Unscrew the thumbscrew.

Start the engine and turn the air conditioner to its maximum cooling setting and medium blower speed. Open the blue valve on the A/C gauge set and allow the can of refrigerant to empty into the A/C system.

Close the blue valve and remove the empty can of refrigerant from the can tap. Allow the engine to run for a few minutes and observe the pressures indicated on the gauges. Add an additional can of refrigerant if the low-pressure gauge reads below 30 psi and the high-pressure gauge reads below 300 psi.

Items you will need

  • A/C gauge set

  • Can tap

  • R-134A refrigerant

 How to Add Freon to a Mercedes

Place the Mercedes in "Park" and turn the vehicle off. Allow the Mercedes to cool down for 20 minutes before beginning any maintenance.

Open the hood and locate the air conditioner unit's low side fitting. The hose connects from the accumulator to the compressor.

Assemble the can of freon by attaching the recharge hose to the valve on top of the can. The hose will snap onto the valve. Twist the can to the "on" position to puncture and open the can.

Connect the can of freon to the low side fitting on the air conditioning unit. Hold the can upright to ensure maximum flow of freon.

Turn the engine on and set the air conditioner to the maximum or highest setting available. This will begin the recharge process.

Continue to charge the system until the can is empty. Remove the ignition key to turn off the Mercedes. Twist the can of freon to the "off" position. Disconnect the can from the low side fitting and close the hood.

Items you will need

  • R134a refrigerant with recharge hose included

 How to Add Freon to a Car Air Conditioner

Attach the recharging hoses to your system. The hoses from the gauges attach to the compressor of your air conditioning system. Attach the shorter hose to the can of Freon.

Open the valve on the can for several seconds to purge the air from the system. Tighten the hose connection again and close the valve.

Start the car's engine and turn on the air conditioner on HIGH. Allow the refrigerant to enter the system by slowly opening the valve for the low-side manifold. Make sure to hold the can upright, not allowing any liquid Freon to enter the system.

Close the valve and remove the hose from the low-side fitting after the can is empty. Be careful when removing the can as there is still some Freon in the can.

Repeat these steps if your system needs more than one can of Freon. Adding too much Freon is worse than not having enough and can damage the air conditioning system.

About the Author

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