Hey everyone,
I’m working on recharging the AC system on my 2015 Mercedes C300 (W205) after replacing a compressor solenoid control valve and ran into a couple of issues that I could use some advice on. Here’s a quick rundown of the situation:

Vacuum Won’t Drop Below -15 inHg on Low Side:

When pulling a vacuum for around an hour, the high-pressure side went down to -30 inHg, but the low-pressure side wouldn’t drop below -15 inHg. The system holds these vacuum values, so it doesn't seem to be a leak, but it’s weird that the low side won’t reach -30 inHg.

I’ve read that this could be caused by a blockage in the system, maybe in the TXV or drier. But since the vacuum holds, I’m not sure. I will add a dye to check for leaks after recharging since I can't get a hold of nitrogen.

1. Could a partial vacuum like this cause issues when recharging with refrigerant, or is it fine as long as the system holds vacuum?
2. Should I try a longer vacuum to see if it eventually pulls down to -30 inHg on both sides, or am I looking at a potential issue?

AC Won’t Turn On During Recharge:

Another issue I’ve run into is that the AC won’t turn on when I’m trying to recharge the system. I think it’s because the refrigerant level is too low, so the system is in protection mode to avoid damaging the compressor. When I push the AC button, the light doesn’t come on.

1. What’s the best way to properly recharge the AC system if I can’t get the compressor to turn on due to low refrigerant?
2. Will the compressor eventually kick in after adding a certain amount of refrigerant?

PAG Oil Amount:

One more issue is that the shop did not tell me how much PAG oil came out during the evacuation of the refrigerant.

1. Should I just add a little bit of oil and then use one of those oil lubrication testers?
2. What’s the best way to purge air from the yellow hose after adding PAG oil? If I unscrew the fitting or press the valve, the oil will most likely come out.

Thanks in advance!