How A Variable Displacement AC Compressor Works

[@ambassadar1]

Thank for the Video Brother. But one doubt, why does a variable compressor have a magnetic pulley? VDCs are running all the time, right?

[@RogueWrenching]

Not necessarily, the whole idea of variable displacement is fuel efficiency, and less load on the engine when the ac isn't on use, a magnetic clutch can take the drag from very low (displacement at zero) to basically zero as the only drag is the bearing on the pulley not a roating assembly. Some have them some don't.

[@DVTOM]

If that pressure valve was stuck closed or open can it raise the low side pressure? I have a Hyundai Tuson that I've checked and the entire system seems compnoants are good, no leaks eitherd which led me to the compressor. I'm going to replace the valve but my low side pressure was pinned high. There is no restriction anywhere in condenser, hoses or evap. So leads me back to compressor. Hopefully the switch replacement gets compressor back to pumping low side to normal pressures again. Would save me $300 for a new compressor if so. It's also a common failure in Hyundai's system.

[@RogueWrenching]

When you say there's no restriction, how are you testing it? If the expansion valve is failed and stuck open that would give you high low side pressure and poor system performance. Also what is the high side doing? Could you have a fan not pulling air through the condenser and high system pressure across the board?

[@jedgr]

Hello, got one Volkswagen clutchless compressor, it is whining when turning AC on and the noise follows the engine RPM... What do you think ?

[@RogueWrenching]

Probably a compressor going bad. Plan on a full ac kit. Compressor, expansion valve, and condenser.

[@chefchutardo5215]

The compressor in my wifes 2016 Scion im (120 000km) works intermitent. I checked pressures and when it works the pressures seem good. But sometimes the compressors just wont go on. is there a way to force the compressor on ? With the old fixed compressors i could just manually power the clutch. But apparently the variable compressors work on pcm signal to vary demand. So i havent dared to send 12v to the compressor wires. Also fan doesnt seem to go into high speed. Fan speed also seems to work on pcm. So im starting to think its an electronic problem. But i would like to confirm before i throw parts at it.

[@RogueWrenching]

You'd need a Scan tool to know if there's a pcm withholding command, and sending 12v to the duty cycled solenoid will fry it in just a matter of seconds.

[@Kebekwoodcraft7375]

What the noise was coming from do you think 🤔 I got one on Mercedes and it makes noise like a fan blade touching something I am on my way to remove it and investigate like a coroner 😊

[@RogueWrenching]

Replace it. there's no fixing these.

[@ghumman68]

Very informative keep it up. Thumbs up

[@RogueWrenching]

Thanks!

[@tanzaniacarschannel6975]

What make these variable displacement compressors fail so early compared to fixed displacement compressors? Can variable displacement compressors being replaced with fixed displacement compressors?

[@RogueWrenching]

Anything is possible but with modern vehicles where everything is connected and monitoring itself for faults, the truck would see a problem with a non factory style compressor, if you could find a fixed displacement compressor that fit (bolted up / line ports match) you'd have to install a relay and pressure switch system to control the compressor, so possible but definitely not practical.

[@teravolt6113]

Mainly that, once the displacement drops, less oil tends to flow back. In a perfectly charged TXV system, once the evaporator is cold enough the TXV drops evaporator superheat so much that some liquid refrigerant makes its way back to the compressor and carries plenty of oil with it (ever heard of closed loop refrigerant flush?). But as the charge level drops enough, less oil is carried around so the compressor tends to run oil starved. In addition, the lack of a clutch allows the compressor internals to keep running with no refrigerant to cool them down whatsoever. Even if there's a valving mechanism that intermittently shuts down refrigerant flow when AC is turned off (basically solenoid valve commanded into lowest displacement operation, in a clutchless system), whether deliberately or due to insufficient high side pressure, so some oil may stay within the crankcase all the time, the compressor never receives any refrigerant to keep it cool (even in the lowest displacement, there's still some friction happening) and the oil "burns" pretty easily, even double end capped PAG. The solenoid valves can also get plugged with wear materials from prolonged low charge (reduced lubricant flow) operation, that's also why they always come with filters/meshes. That's why they fail easier (especially the ones with no clutches) compared to fixed displacement ones.

[@sandalbasotra5765]

I replaced the variable type compressor to a fixed angle ac compressor in my skoda. Mine failed at 60k miles. And the later ones are cheaper and cools good enough.

[@sandalbasotra5765]

@Rogue Wrenching. It is definitely practical. Trust me bro. It works smoothly.

[@tanzaniacarschannel6975]

@@sandalbasotra5765 i did convert mine from variable displacement compressor to fixed displacement compressor after having bad experience with fixed displacement compressor... What i did was to modify wiring(i maintain the solenoid from old variable displacement compressor, then i connected the relay for magnetic clutch of fixed displacement compressor. The modification seem to be durable compare to variable displacement compressor though there slight differences ie when clutch engine you hear click sound and small shake but it works so fine.

[@nurfitriyadi4469]

hello brother... is it true that the function of the solenoid control valve closes the channel and opens the refrigerant channel

[@RogueWrenching]

I'm not sure I understand your question. The solenoid valve changes the angle of the swash plate, thus changing the displacement of the compressor. When the solenoid goes bad, it defaults to 0, i.e. no displacement or no flow, which makes the ac system stop working.

[@nurfitriyadi4469]

@@RogueWrenching I mean..which makes the angle change..because there is a flow from the solenoid?

[@RogueWrenching]

@Nur Fitriyadi I am not 100% sure you be honest, I think its magnetic, but I wouldn't bet my paycheck on it.

[@nurfitriyadi4469]

@@RogueWrenching ok bro..thank you for wanting to reply.and sorry if there are wrong words..I also don't speak English very well

[@RogueWrenching]

@@nurfitriyadi4469 All good friend, I wish I could have been more help.

[@cheapers1952]

Great concept but like you said LESS than 100,000 miles I see a very large amount of this type of compressor failure at less than 100,000 miles many of the turn of the century 99-2004 gm trucks get around 200,000 +plus miles before a failure

[@RogueWrenching]

Exactly. It seems like the failure isn't mechanical, it seems like making the electronic part serviceable would extend the life by a lot.

[@MGregolin]

Great video but I disagree of making a perfect state piece into the junk just for a simple control valve that could be replaced easily.

[@RogueWrenching]

Yea, making the solenoid serviceable would be nice. It'd save people a lot of money.

[@Outcazt_Fishing]

Great video brother👌🏽👌🏽

[@RogueWrenching]

Thanks!

[@steveneddy9305]

Informative, i learned

[@RogueWrenching]

Thanks for the feedback

[@tanzaniacarschannel6975]

Probably you were to change the solenoid valve and compressor could back to life

[@RogueWrenching]

I'm 90% sure you are correct, the problem is no one makes a new solenoid and it's made to be not serviceable so replacing without damaging may be challenging. But I agree, mechanically speaking the inside of this compressor looks fine.

[@teravolt6113]

Oil looks kinda dark, ran with too little refrigerant maybe? Valve/meshes may just be gunked up and need a good cleanup

[@RogueWrenching]

@@teravolt6113 truck had a full charge when it came into the shop, and it had equal high and low side pressures. There was minimal signs of wear anywhere in the mechanical side of the compressor.