No, the lowside service port for rear AC is not the same as the front. The lowside service port is located, in most vehicles, just beneath the back seat on the driver's side.
There is a web site www.idqusa.com where there is helpfull information about your vehicle ac system. There is a lowside port locator on there.
Connect your Freon bottle to the low pressure port on your 1995 Lexus. Release the Freon into the air conditioning system.
the lowside port would be located on passenger side up near firewall the will be your ac canaster as it will have the port right on it
Its on the Receiver Drier. You can find a good spec drawing on the website below. Just click on the "Locate low side port" and follow the instructions.
It depends where the port is located, Compressor, Reciever/Dryer, Accumulator on a hose. it has been my experience you can not change the port but you have to replace the whole part that holds the port unless it is the valve inside the port you can replace those.
try first with freon
Could be you are low of R-134a. You can check the PSI level on the lowside with a gauge and if you are you can add R-134a. Any automotive store and some discount stores will have R-134a and gauges. Also you can check out the videos on the link below with show how to add R-134a to you car, and where to find the lowside port.
On the drivers side next to the air filter box
connect an ac gauge and freon to the low side ac port. Start the engine and turn ac on high. Open the freon and watch til the gauge shows full.
There should be a sticker in the engine compartment with the AC refrigerant and oil quantity information.
its located on the bottom of the compressor drivers side of the motor behind plastic panel which is behind wheel