Air conditioning compressor swash plate vs. clutch

[john_gonzo]

I've noticed a lot of posts about air conditioning compressors with confusion about clutches. This post is an attempt to help others who have a failing/bad compressor and are curious about the design used by Audi.

The AC compressor on our cars has no clutch. Some vendor sites may lead you to believe otherwise. Here are a couple examples from a recent post.
http://www.carpartswarehouse.com/add.../60-01751.html
http://www.nextdayauto.com/2003-audi...3-1912403.html

On our cars, the center of the compressor pulley where a clutch normally resides is filled with a rubber and steel coupler. The coupler transfers power from the pulley to the compressor shaft. This coupler is designed to fail in the event of compressor seizure (or high torque demands which herald seizure). This protects the serpentine belt (so you can get home) and the rest of the AC system (a compressor that doesn't grenade won't spew fragments into the condenser).

The function of the clutch is handled by a swash plate internal to the compressor. Not just handled, one-upped really. Here is one of Diagnosticator’s excellent posts describing the function of the swash plate design:
http://www.audizine.com/forum/showth...=1#post5913687

Here’s a functional diagram video of a variable displacement piston pump. The Audi AC compressor falls into this category. Note that the pistons only move up and down in their sleeves, they don’t rotate about the centerline of the compressor shaft.
http://www.youtube.com/watch?v=2mh902AP7Yw

Below are pics of the internals of the worn AC pump from my 2003. This pump chewed through two couplers within a few months. The piston sleeves were gouged and many of the bearings were failing as well. The failed coupler is visible inside the pulley in the first pic. The unseen center portion of the coupler attaches to the rusty splined shaft just visible inside the compressor housing.



Reed plate and pistons:


Pistons unsleeved:


Each piston rides both sides of the swash plate on top of hemispherical pucks. In this image, the near side puck is visible under the piston. The far side puck is captured by an extended “hook” portion of the piston between the swash plate and compressor case. Whole pistons are visible in the background of later pictures.


Swash plate near minimal pumping displacement. The coupler attaches to the splined shaft.


Swash plate at maximum pumping displacement:


Hope this helps. Comments and feedback welcome.

[Toolaa]

I'm a big fan of knowing "how things work" and usually jump at the chance to rip apart any broken part on my car. Thanks.

[Charles.waite]

Awesome dissection. I always wondered how these variable displacement pumps functioned. As an aside those pistons look a lot like brake pistons.

I assume your compressor was beyond reasonable repair? Or were you able to replace the bearings and put it back into service?

[old guy]

Way cool! Thanks for posting!!

[john_gonzo]

Yeah, it was an interesting teardown. The pistons were very light weight for their size. Charles, you are right - it was beyond salvaging. The poor condition of the sleeves was the kicker even though I was willing to hunt for bearings, including this one which rode on a machined surface inside the front cover:

[fabric8]

John and other experts, I ordered a compressor kit to replace my AC compressor whose pulley bearing died (the compressor itself seems fine and my expansion device (orrifice tube?) was clear and clean - no sign of metal particles.)

In any case, the AC compressor I received doesn't have the same pulley as mine. Customer service claims it's compatible.

From the looks of it, could it be a newer version of the pulley coupler? Has that been re-designed? FWIW, when I spin it, I do hear what sounds like the oil inside the compressor moving, which suggests it's spinning and is directly connected.

Here are pics of the compressor I received next to my pulley:

[john_gonzo]

John and other experts, I ordered a compressor kit to replace my AC compressor whose pulley bearing died (the compressor itself seems fine and my expansion device (orrifice tube?) was clear and clean - no sign of metal particles.)

In any case, the AC compressor I received doesn't have the same pulley as mine. Customer service claims it's compatible.

From the looks of it, could it be a newer version of the pulley coupler? Has that been re-designed? FWIW, when I spin it, I do hear what sounds like the oil inside the compressor moving, which suggests it's spinning and is directly connected.

I'm no expert, that's for sure!

I posted a reply in your other thread.

[DiertyEuroSpec]

Fabric8 did you order from discountac? If so I had the same compressor with that larger pulley. Just to confirm it has 7 grooves or fits a 7 groove belt as opposed to our 6 groove belt correct? I put that compressor on just to figure out the pulley was over sized in diameter and had 7 grooves so even if the serp belt fit, which it did NOT it would wander and possibly throw itself off. I then had to take it back off and send it back for the correct one.

BTW this was explained in the other A/c thread you are posting in as well.

[fabric8]

I did order from discountac, and funny you mention it, but the 1st compressor they sent me had a bigger pulley with 7 grooves - just like you experienced. After emailing pictures to customer service comparing the two, they shipped me this one you see in the pics. It's the same style pulley as the 1st one they sent, but this one has 6 grooves and is the same diameter as the one on my OEM Denso.

When they shipped you the replacement, was the pulley the same style (as what I have now)? or was it identical to the OEM denso? and how is yours holding up?

[DiertyEuroSpec]

I don't really remember the style of it but I wouldn't stress that, as even though it has a diff appearance still functions the same. I changed it at the end of last summer and have no issues with it, even though I haven't used ac at all recently.

[gmudan]

Sorry to bring this back, but whats the difference between the 03 compressors and 05. ECS says split is in the 04 year. Need a new one for my 05...

[diagnosticator]

The compressor pulley has a revised drive release hub design compared to the rubber block type used earlier. The pulley hub releases if the compressor seizes up, allowing the accessory drive belt to continue driving the alternator, etc.

[cschuster]

The compressor pulley has a revised drive release hub design compared to the rubber block type used earlier. The pulley hub releases if the compressor seizes up, allowing the accessory drive belt to continue driving the alternator, etc.

Does it matter which one you use if the difference is just the pulley hub design?

[Apexmaster32]

how hard is to remove the compressor? any special tools needed? what about when disconnecting the refrigerant? I am having issues with my AC, It does not blow cold. i was told if my compressor does not work. my ECON button will stay light up and i would not be able to turn off. also when i click from Off to Auto i should hear the compressor turning on, and the engine RPM would dip down for a second. I have also checked all fuses and relay .
my car is a 2004 A4 Quattro 30v 3.0 v6 6spd manual

[fabric8]

The compressor itself is easy to remove with basic tools (on a 1.8t at least). First, remove the accessory belt. Then discharge the refrigerant. Then disconnect the electrical connector to the compressor. Remove both AC lines to the compressor. Then remove the 2 bolts that hold the compressor and you're done. If my memory serves me right.

But before you go through all this, have you checked to see if you're low on refrigerant?

Sent from my SM-G900F using Tapatalk

[eljay]

how hard is to remove the compressor? any special tools needed? what about when disconnecting the refrigerant? I am having issues with my AC, It does not blow cold. i was told if my compressor does not work. my ECON button will stay light up and i would not be able to turn off. also when i click from Off to Auto i should hear the compressor turning on, and the engine RPM would dip down for a second. I have also checked all fuses and relay .
my car is a 2004 A4 Quattro 30v 3.0 v6 6spd manual

ECON light is triggered by the pressure sensor at the condenser when you are low on refrigerant. I would check the pressure in the system first if you have means to do so. A good shop would be able to hookup their equipment to it and tell you in 2 mins. When there's no pressure, the compressor will not engage to protect it. Also, circulating refrigerant is good for the health of the compressor, so if this just happened, don't delay the check to avoid compressor damage.

If refrigerant is low, it leaked out somewhere and you'll need to find the leak and fix it before refilling as you would loose that refrigerant again.

Check the above first before replacing the compressor.
I just serviced my system as my compressor seized. It was obvious because the rubber isolators fell out.

[Tommy5150]

What a great post!! Great Job!!