New compressor charge - problems

[romeroom]

I'm hoping this forum can offer help since car specific forums have been very slow to respond.

Car is a 2006 Volvo XC90. My son bought it and was told the a/c compressor had been replaced but never charged with refrigerant. Here are some of the things I've done and results:

1. I pulled a vacuum for 30 minutes, closed the manifold valves, and within an hour the needle was back to zero. Obvious leak.
2. I removed schrader cores, put in some die, and replaced the cores with new ones, making sure to lubricate the core rings.
3. I pulled a vacuum as in step one and the results were the same.
4. I pulled a vacuum for more than an hour then proceeded with adding approximately 18 ounces of refrigerant while holding the RPMs at 2000.
5. The low side pressure gradually went up to about 30, dropping as expected to around 20 when the compressor kicked in.
6. The high side, however, stayed near 10 the entire time; warm air coming from the vents.

While finding the leak will be important, getting cool air I suspect should be first priority.

I'm a newbie at this. I suspect there is an expansion valve somewhere not functioning properly; a lot of the connections and a/c tubing is well hidden.

What are some thoughts?

[Cornbinder89]

High side can't be lower than low side, so I would guess your high side is not connecting to the system. 30 psi is too low, you don't even have enough refrigerant in to equal the vapor pressure at ambient temp.
You need to charge by weight, but really need to find the leak before anything else. Compressor may or may not have been replaced, I put very little confidence in stuff that was "supposed" to have been done.
Unless you know for a fact the compressor was changed AND the correct amount of oil was used at the install, I would pull back out and make sure (drain the oil and make sure to re fill with the correct oil and amount)

[romeroom]

High side can't be lower than low side, so I would guess your high side is not connecting to the system. 30 psi is too low, you don't even have enough refrigerant in to equal the vapor pressure at ambient temp.
You need to charge by weight, but really need to find the leak before anything else. Compressor may or may not have been replaced, I put very little confidence in stuff that was "supposed" to have been done.
Unless you know for a fact the compressor was changed AND the correct amount of oil was used at the install, I would pull back out and make sure (drain the oil and make sure to re fill with the correct oil and amount)

Thanks so much for your reply. I after I posted my question I realized there is a "Rear Air" button and followed some refrigerant lines towards the back of the vehicle underneath before they disappeared. You are correct in there not being nearly enough refrigerant in the system. I am having a hard time finding specs on what is needed in terms of refrigerant volume, but I'll continue looking.

Obviously, I am very new at this. I appreciate your guidance.

[Cornbinder89]

Inspect the lines running to rear for damage, corrosion, they may very well be where the leak is.