The low pressure (vacuum) side.
your freon is measured with gauges hooked up to low side of air condition unit the low side is the cold side high side is the condenser side WATCHOUT high pressure every unit has atag on it and let you know how many ounces to be put in low charge is bad but over charge is also bad
By buying an AC charge hose and a can or 2 of R134a freon (depending on how much your car needs) Attach hose to the low pressure side & charge system. Do not overcharge, or you may destroy the AC system.
The high pressure side.
The same as you would with a single a/c system, charged on the low side service port. If you connect a small can of Freon to the high side with the system on, the can may explode from the high pressure introduced into it.....
From the same port you would charge the front ac this is under the hood on passenger side of vehicle. John
To charge refrigerant gas in a split AC unit, first ensure the system is off and locate the service valves on the outdoor unit. Connect a refrigerant gauge manifold to the low-pressure side, then attach the refrigerant canister to the high-pressure side. Open the service valves and allow refrigerant to flow into the system, monitoring the gauges to maintain the proper pressure levels. Once the desired charge is achieved, close the valves, disconnect the gauges, and run the system to check for proper operation.
The AC low side service ports for a 99 Oldsmobile Aurora are located on the AC unit. This unit is located between the engine block and the back firewall of the vehicle under the hood. The service port is typically the largest port on the back of the AC unit.
300psi high side and 80psi low side
The low side of an AC system begins at the metering device outlet and ends at the compressor inlet.
To measure a window for an AC unit, first measure the width and height of the window opening. Then, ensure there is enough space on either side of the window for the AC unit to fit. Finally, consider the window type and installation requirements of the AC unit to ensure a proper fit.
The low pressure side of the ac system is the ac hose that runs from the inside of the vehicle to the ac compressor. The high pressure side runs from the ac compressor to the condensor in front of the radiator. Follow the ac hose from the compressor back to the body and you will find the charge fitting. It is smaller in diameter than the high pressure side. You would need a different adapter to hook up to the high side.
Fittings for 134 freon