Air Conditioner Vaccum and Recharge
- Air conditioner recharge gauge set
- 134a refrigerant
- Refrigerant recovery machine
- Protective eyewear and gloves
Refrigerant Recovery Machine Step 2 - Connect an air conditioner gauge set to the recovering machine and open the low side valve to start the recovery.
Low Side Pressure Connection Vacuum Down and Recharge Step 1 - An air conditioner gauge set or recharge kit is needed to connect to the system on both high and low side pressure ports, a gauge set will also be used to vacuum down and recharge the system, inspect all hoses and connections. 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 a recovery machine or a new refrigerant supply bottle, both gauge valves should be closed.
Air Conditioner Refrigerant Pressure Gauge Set Step 2 - Beginning with system pressure at zero, by the way of recovery or repair, start by locating both high and low side service ports, these locations will vary and can be obscure. (Note: a high pressure port is always larger than the low side port.)
High/Low Side Pressure Service Ports Step 3 - Once located, remove both high and low side dust caps.
Remove Dust Cap Step 4 - While pulling the retainer ring backwards, press the valve over the service port, repeat this for both service ports. (Note: High and low side fitting will only work on there respective ports.)
Attaching Gauge Valves Step 5 - Once secured, tighten the valve which activates the internal plunger that opens the service port valve on the refrigerant lines.
Tighten Valve Step 6 - With both gauge valves closed, there should be little to no pressure in the system.
No Pressure Step 7 - Connect the center hose (yellow) to vacuum pump or recovery machine and turn "ON", this step is used to remove any moisture and static air from inside the system.
Connect Hose Step 8 - Slowly open the low side gauge valve, the pump will now start pulling vacuum throughout the system.
Opening Low Side Gauge Valve Step 9 - Once the vacuum has been on for 25 to 30 minutes, close the low side valve, the system should hold at 29 in., turn the vacuum pump or recovery machine "OFF" (Note: If the system loses vacuum there is a leak).
Holding @ 29 inches Step 9 - Disconnect the yellow hose from the vacuum pump and attach it to a new 134a refrigerant source. (Note: Many recovery machines have a charge feature that can be used.)
134a Refrigerant Step 10 - Open the keg valve
Open 134a Refrigerant Keg Step 11 - While the gauge valves are closed and once the refrigerant source has been opened, the gauges will respond with equal reading on both high and low side, this is static pressure which will vary depending on outside temperature.
Static Pressure Step 12 - Turn the keg over which expels liquid refrigerant instead of gas, this will help expedite system charge time, most systems hold about 2 pounds, a digital bathroom scale under the keg can aid in the recharge process.
Turn Over 134a Step 13 - Next, start the engine and turn the air conditioner "ON" to the highest settings including fan speed.
Air Conditioner On Step 14 - Slowly open the low side (blue) valve (never open the valve completely.) Refrigerant will start to flow to the low pressure port. (CAUTION: Never open the high side (red) valve, this will fill refrigerant container with super high pressure and may cause a rupture.)
Refrigerant Flow Step 15 - The compressor operation will begin which will be followed by the low side pressure dropping, while the high side pressure starts to rise.
Low Side Drop - High Side Rise Step 16 - Continue adding 134a until the gauges start to look like this. If both gauges are too high the system is over charged 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. - Replace air conditioner compressor
Typical Gauge Readings Step 17 - 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. (Note: Monitor the refrigerant scale weight to help determine a complete charge.)
Monitor Outgoing Temperature Step 18 - Once the system is performing properly close the low side gauge valve (Note: Do not overcharge).
Close Low Side Gauge Valve Step 19 - Turn the ignition switch off, the A/C system will shut down along with the engine.
Turn Key Off Step 20 - With the engine off, release the valves effectively closing the service port, repeat this procedure for both valves.
Loosen Valve Step 21 - Firmly grasp the valve retainer and pull up, this will release the valve from the service port, repeat this procedure for both valves.
Release Valve Step 22 - 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!
Reinstall Dust Caps Helpful Information Automotive air conditioner systems have a mixture of refrigerant and oil to keep the air conditioning compressor lubricated during operation. Measuring the amount of (pag) oil is difficult in the system 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 oil, unlike a very small leak which releases little to no oil. Oil can also be drawn out from the system during the evacuation process, if this occurs add new oil in its place, never re-install used oil. There are two separate occasions in which an air conditioner system needs to be recharged, a normal condition of residual seepage, or when a repair has been performed such as replacing a leaky compressor, condenser or evaporator. Once the system has been opened it must be held under vacuum for a period of time (usually 30 minutes) to remove moisture. The AC system will not work correctly if the engine is overheating or running hot. Common Problems
- Failed compressor
- Refrigerant leak
- Plugged orifice tube/expansion valve
- Failed vent control system
- Shorted control switch or relay
- Plugged condenser or evaporator (cooling fins)
- Use a garden hose or compressed air to clean the condenser at the front of the vehicle to ensure maximum system performance.