A/C issues in July after recently rebuilding.

[13JRomee]

Hi Happy HOT July!
2002 Tahoe LS 5.3L
A/C Orifice issues Getting the correct size and type.
I rebuilt the A/C did some modifications blanked off the rear >>> it didn't work upon buying. Kept the big size condenser, it's new as are the lines, accumulator, evaporator, compressor.
I installed a larger diameter GM orifice tube that is .072. Sitting in town going under 30 or so it's freezing cold. Get out on the road and it gets kinda muggy inside and the A/C feels like it is failing. Get back into a town or slow down and it's freezing again. Out on the road it gets muggy
A friend of mine that is an A/C guy threw his gauges on it. My friend noted that the low side is tripping/dumping. The compressor is cycling often. The high side pressure and temp is a bit above normal. My friend said that's not a big concern. And the system seems to be fully charged.
The orifice tube GM Genuine pats #3096068 is what I installed.
At 1000 or so RPMs the compressor is cycling quite abit.
I'm hunting a smaller diameter tube.

 

[nonickatall]

You don't need a smaller diameter line; you can simply add a little more refrigerant.

If you have a friend who works on air conditioning, have them add 50g more refrigerant to the system and check the pressure gauges. That will tell you if the amount is correct. If it's not enough, just add more in 50g increments until it's right.

My motto is: never open a sealed system...

 

[13JRomee]

I've lost track of the amount of 134a I've put it the system. the normal amount according to GM specs for the 1.8 pounds for a single system. The dual is 3 pounds >>> with A/C in the rear.
Since I'm running a mix of components single/dual mix of stock components it's changed the system capacity to unknown.
I'm in agreement with don't open the system>>>> unfortunately I'm going to have to once I get the correct smaller diameter tube.
I've all the equipment to do the work just hate messing with it.
Now my friend with the gauges is almost insisting I get the A/c in the rear going. He keeps pulling up info on the rear expansion valve.

 

[nonickatall]

So, if the low-pressure side has a too low pressure and the system shuts down as a result, that suggests there's too little refrigerant in the system overall.

The high-pressure side is irrelevant for now.

I wouldn't replace any lines; why bother? I'd simply add more refrigerant, and that should fix it.

It's also possible that the expansion valve is too large, causing the system to run too cold. This would be problematic because the expansion valve could freeze, which in turn would cause the system to suddenly lose power at higher speeds or engine loads.

You can check this by inserting a thermometer into the blower vents. The temperature at the coldest setting shouldn't drop below 3 degrees Celsius.

I would also reactivate the rear air conditioning unit. The common problem with our cars is that the refrigerant line running from the front passenger side to the rear air conditioning unit is corroded, and when I bought my car, the rear air conditioning was also disabled.

I then noticed that the air conditioning wasn't very good, especially in the hot summer; when passengers were sitting in the back, it didn't really cool them down. I then repaired the lines and put the system back into operation, and now the system is fantastic.

When I start driving in hot weather, cold air comes out immediately, and the car cools down quickly.