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I have a 2013 Nissan Rogue. The ac is not working and I am attempting to fix it by replacing the ac clutch, pulley, and coil. There is something I don't grasp about how the ac compressor works.

My understanding is that when the ac coil is activated, it generates an electromagnetic force that draws the clutch towards the spinning pulley. When the clutch and pulley engages, torque is transferred to the shaft of the ac compressor, making the cooling cycle possible.

What I don't understand is this: where is that 'play' that makes it possible for the clutch to be drawn towards the pulley when the ac coil is activated? I have just installed the new coil and pulley and clutch, and I notice that everything is screwed on tightly with no play at all (there is an air gap between the clutch and the pulley; but the gap is fixed and I can't close it by pushing against the clutch). I don't see any spring anywhere that would give the clutch any play.

So what gives that allows the clutch to move towards the pulley when the coil is activated? Should the shaft of the ac compressor move axially if you push against it? I have tried but the shaft of my ac compressor does not move inward or outward.

I have not yet tried starting my car to test the new parts because I am afraid that the source of the problem may be something else.

Thank you for your help.

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2 Answers 2

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Here's an old AC compressor clutch hub i have in my possession.

enter image description here

It's pretty simple, actually. Any clutch hub is made of two parts. A friction disc and the actual shaft plate. The friction disc is what's really pulled upon the pulley once the clutch coil gets energized. The shaft plate remains stationary on the compressor shaft instead, not moving neither backwards nor forwards.

One or more flexible elements (which can be a rubber ring, a set of rubber pads or a set of metal "leaf" springs) is/are what separate/s these two parts.

enter image description here

In my clutch hub, the flexible elements are a set of three rubber pads. Pressing the shaft slot forwards (what the stationary compressor's shaft is effectively doing) and the friction disc backwards (what the clutch coil is doing through an electromagnetic field) widens the gap between the two parts, effectively making the friction disc retract backwards. This is what happens when you turn AC on. While moving backwards, the friction disc eventually contacts the pulley's friction surface and the compressor shaft starts rotating together with the engine shaft as a result. Obviously, whenever the compressor clutch coil stops getting energized, the flexible element recalls the friction disc forwards into its original position.

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You can't normally press on the outer portion of the clutch and have it engaged. The part that moves is on the backside of the exposed part. The entire clutch plate doesn't move, just the inner part that contacts the pulley.

To test it with the engine off, you can apply 12V to the coil and you should hear it engage. If not then you have an issue with it.

Clutch Pully Coil

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  • Thank you for your prompt reply. Could you please clarify where is that part that moves "on the backside of the expose part"? Is the part that moves part of the coil/pulley/clutch, or is it inside the compressor? I will surely test with a 12V. But it would be nice to know where the moving part is that moves when the clutch engages. Right now I just don't see how anything can move: neither the pulley, nor the coil, nor the clutch, nor the compressor shaft moves axially (at least when the engine is off). If nothing moves axially, how can the clutch close the air gap and engages with the pulley?
    – Joseph C.
    Commented Jul 2, 2020 at 14:17
  • The "part that moves" is between the front plate and the pulley. I suspect it's called a clutch plate. See the image I added to my answer.
    – jwh20
    Commented Jul 2, 2020 at 14:21
  • I do know that the clutch plate moves to engage with the pulley, but for the clutch plate to move it has to have some 'play' that allows it to move axially towards pulley when the electromagnetic coil is activated and to slide backward (or outward) and disengage when the coil is off (btw, what is the 'front plate' you are referring to if it is something other than the clutch plate?). My question is where is that 'play'?
    – Joseph C.
    Commented Jul 2, 2020 at 14:26
  • If you turn the clutch plate, you'll be turning the compressor whether the clutch is engaged or not. The clutch plate should be directly attached to the compressor. The clutch itself is part of the pulley (as seen in the picture above ... the annotations on the image are a little misleading.)
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented Jul 2, 2020 at 16:00
  • Hi Paulster2. My understanding is that pulley and the clutch plate (I don't know if by 'clutch' you mean the clutch plate) are two different parts. They touch and engage when the ac coil is activated, transferring the torque to the shaft of the compressor. My question above in relation to how the clutch moves towards the pulley remains.
    – Joseph C.
    Commented Jul 2, 2020 at 16:15

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