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I notice there are two posts asking nearly the same questions of the same years cars. I might post this on both sites.
This might get lengthy and most likely will not answer all questions in one fell swoop!
The low side is always the largest line of the two going to the compressors body.
You want to fill from the low side with gas only. If your gauge line are long enough you can tip the canister quickly to splash liquid into the line to speed up charging if you have not pulled a vacuum on the system and are just topping it off.
If you see the fittings on the lines either at the compressor or on the gauges to start getting frosty, you must slow down tipping the can for liquid! You mainly want the gas with only big droplets in it to boil off. Liquid does not compress and will wreck the compressor!
On your car since it uses a thermostatic expansion valve it can tolerate a slight overcharging.
The glass window is used to tell you when you have only liquid going to the evaporator. That's when you stop charging.
It will turn totally clear and stop having bubbles flowing by the glass window. Stop as soon as it stays clear. If the compressor cycle on and off the bubbles might appear but only about for a second. That is a good charge and will not raise the head pressure excessively in the hottest temperatures.
As far as making the car cool better, you need to check the output of the TXV mentioned above. Some are adjustable with remove able caps on the bottom and some are not. If you will notice there are two tubes that control the TXV on this car.
One is an equalizer to compensate for pressure drop across the evaporator. That is something you can not mess with. In the picture, you now have, its the one with the nut on that large line.
The next line is the liquid sensing line that determine the amount of liquid allowed to flood the evaporator core. Ideally you want it 75 to 80% filled and have the rest of the space left for boiling into gas or what is called superheated gas. From the equalized point connection to the compressors port is all part of making superheated gases.
This is checked by reading temperature of the tailpipe of the evaporator and comparing it to the suction pressure that both will correspond to a temperature/pressure relationship. You want to see a difference of 5 to 7 degrees.
The adjustment is done by relocating the sensing tube up or down the tailpipe. In some case insulating the tubing from the tailpipe tube with plastic strips or tape so it will not get as cold as quickly.
This will make the TXV think is warmer and it will allow more liquid to flow in.
One has to be careful to not get the sensing line TOO insulated as to cause a flood back condition. It would be like when charging the system and having liquid get back to the compressors pistons and valves.
Doing this, with caution mine you, is like adding more water onto the fire but you want to keep getting steam back to the compressor!
On my '78, '84 & '86 I have it clamped farther out away from the evaporator by just a inch or two and I used a thin piece of plastic. My unit runs quite a bit cooler than it did when I got the car from its original first owner.
It works so much better that I do not have to run the thermostat knob on maximum on trips! If I did I think it might ice up with frost as that is your anti-frost/deicing safety switch.
As an added note, these adjustment should be set up with or against your local climate of humidity in mind. Another reason to monitor your low side pressures on any system for superheat performance!
All of this may seem tough to grasp but a study of the basic refrigerant life cycle will clear things up for you! Lots of courses and books are very self taught friendly. Automotive and home are virtually the same, just one box moves around faster with different sizes of components in it!
It not that hard, I learned it!
Phil
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