Finding a restriction in the A/C system Part 1

[@josueferman6562]

You have earned my like😮😅 Great job explaining having problem my self

[@davemaciel1391]

You for sure have talent to explain how things operate. Great videos. I would like to know if static pressure is a good indicator for the condition of an AC system. From what I read, there is a good relationship in pressure and ambient temperature. If so I don't understand why on a vehicle the static pressure is 110 on both sides when the ambient temperature is only 75 degrees. Any help would be appreciated. Thanks!

[@ProfessorPentane]

Hi Dave, it is really underhood temperature. So, if the engine is hot, 110 could be the static pressure. Check again when the engine is the same temp as ambient and it should be around 75. Good luck and thanks for watching.

[@CHIBA280CRV]

Thank you Professor, I appreciate your video.. I wish I had a machine like that.. my 2007 Honda CR-V ac won’t kick on.. I jumped the relay and got the compressor took ion and my high side numbers went up high , I would assume a bad compressor and or TXV.. I don’t expect you to know being the car is not there just a thought..thanks sir.

[@GL_AutoVibe]

Awesome explanation! Thank you very much.

[@Swenser]

Quick question. Without the compressor running. Pistons inside may be sitting at a spot to be a restriction. Right?

[@ProfessorPentane]

Correct, with the compressor not running, the inlet and outlet reed valves on each cylinder will close and cause a normal restriction through the compressor. Thanks for watching.

[@moreykowalenko583]

thank you so much learned lots. I have a dodge 3500 that low side is 8#s and high side is changing from 100,150, 250, 300, at shop temp of 66 f

[@richarddesimone960]

I was wondering if the expansion valve, Compressor Control valve or the hvac system switch could be causing my line pressure to be high on the low side. Above 660 psi. No leaks. I drained the system down and tried to fill it to 55 psi on 90° day 12% humidity. I let sit over night and checked again but was right back to over pressure. Luckily no burst. I did attempt to drain it again to normal pressure. Leaning to a bad compressor. But wasent sure exactly. And buying the 3 parts to change is about the same as a new compressor. I will test them and see if they are at proper voltage. I did check all fuses and fan is working.. Not sure what to do now. 95° and getting hotter here on the east coast. Not sure how to even check if any of the parts are functiong after I check voltage. Engine does change when I turn on the AC. The idle does come up about 500-600 rpm. Please if someone can help me .

[@ProfessorPentane]

Hi Richard, I need to know what the low and high side pressures are and which lines the service ports are in to help any further. PP

[@georgethomas4195]

How can you possibly test a system with only 75 PSI on the high side you should have approximately 50 on the low side and 225 on the high side depending on ambient temperature.. those pressures you saw look like a system that did not have enough freon in it I am ASE certified master and I would never try to diagnose a car that doesn't have the correct amount of freon you should have evacuated it and recharged the system to correct amount of freon... If it has a restriction it will pull the low side into a vacuum and the high side will go up to three or 400 PSI ...You're not working on my car pal...

[@ProfessorPentane]

Sorry George, but you are wrong and do not know what you are taking about. If there is a low side restriction, the low side will drop and high side will go down, not up. Just watch my videos on my channel and I have lots to prove this point. A low side restriction, like in the TXV, DOES look like an undercharged condition. That is why I have this video. What you said is a common mistake by tech who really don't knowing how A/C works. I have heard it dozens of times before in the A/C classes I teach for Techs. Sorry.

[@cognac8297]

​@@ProfessorPentaneThat's right and basically that other guy that said the high side goes up would have not fixed the expansion valve and would have a bring back lol. He needs to stick to Prius. Cause you even said it could look like a low freon. But the other guy wheels would fall off his car he can't work on mine cheap labor

[@hetori9918]

so if the low-side hose/evaporator is restricted, the low-side gauge still shows pressure after the recovery process with a closed valve so the whole AC system is connected, if blockage exists, the gauge will tell you which side and how bad it is?