Variable Displacement AC compressor question

[chaosthyre]

Hello,

I purchased a 2020 Chevy Equinox Variable Displacement AC compressor to tear down. I understand the basics of how it works, however, when I turn the hub, I can hear what sounds like suction sounds, but when I put my finger over the suction and discharge ports there is no suction or pressure. I believe when an ECVD compressor is off that the control solenoid has the high side port open to the crankcase to keep the compressor at minimum displacement because pressure is equal on both sides of the piston, but it has to pump something in order to create some suction pressure when the solenoid is energized, opening the suction port decreasing the pressure in the crankcase which will cause the pistons to displace to maximum displacement and it regulates displacement as needed. Am I correct about this? I have read somewhere when the solenoid is not energized it creates a bypass between suction and discharge on some compressors and most of the refrigerant recirculates instead of going into the circuit. Maybe both are correct? When the compressor is turned by hand when the solenoid is not energized, is the refrigerant recirculating because there is a bleed hole that is always open to the suction side and the flow is taking the path of least resistance, and when the compressor is actually connected to the engine running very fast it will start to build pressure as the bleed hole cannot bleed the volume the compressor is pumping at high speeds?

I'd appreciate any insight on this!

Thank you,

-Mike

[Tom Greenleaf]

Welcome. Did I read that right? You purchased this compressor to take it apart and witness it's functions?

Newer to me if you also have a way to simulate it turning at real engine speeds and conditions has to be a must or the vehicle it can work in?

I/we don't design the parts that make A/C work we try to understand them fully for when a system doesn't not work.

What is your objective?

[chaosthyre]

Correct, I guess I am looking for resources that give a detailed description of what happens when a clutchless variable displacement ac compressor is off/minimum displacement. Does the solenoid valve open in such a way that it opens the suction and discharge ports equalizing the pressure on both sides of the piston and the minimal amount of refrigerant pumped mostly recirculates within the compressor, or does it open the high side to the crankcase to keep the pistons at minimum displacement by keeping the same pressure on both sides of the piston?

Thanks,

-Mike

[Tom Greenleaf]

I've retired before these were out there. All common sense "compressor" has to about quit so it doesn't try to compress oil carried by liquid refrigerant also must shut off a clutch set up or ''hydraulic lock'' wouldn't be nice!

Hence use of pressure switches with info at what conditions (if) the correct refrigerant is in system would be all wrong.

It's quite a show of engineering to "remove" heat so cooler air is possible,

[Cornbinder89]

I think I saw a breakdown on these "clutchless" compressors and they are wobble plate that goes near 90 deg so no piston movement.
Like Tom, they came out after my time and I never had anything with one. They also have a shear plate that will let go and allow the pulley to free wheel if the compressor locks up.
Sorry I can't be of more help.

[Cornbinder89]

Are you sure they aren't using a oil pump and lube oil to move the displacement? That would be the way I'd design it. Loose oil and the compressor goes to no compression. Use a varying pulse width (PWM) to control how much displacement while in use. Refrigerant wouldn't have to move at all when not needed. Many pumps have pressurized oil, starting with the A-6. Many were splash lubed, but with so much moving in a variable displacement, I would use a lube pump.