# Rogue AC Compressor Question



## raylo32 (Nov 25, 2006)

Not sure they are all the same but the pulleys don't really move. The clutch, when energized, locks the outer pulley where the belt rides to the inner hub that is connected to the compressor shaft. When de-energized the outer pulley just freewheels.

What did you check before you did all that work? There are a few things in that circuit to energize the clutch... the switch, a relay, and refrigerant pressure switches. Did you check any of that or especially the refrigerant charge? The most likely problem is that you have a leak and are low on refrigerant, which will set the LP switch and prevent the clutch from energizing. One way to test this is to jump the relay to directly energize the clutch. You can usually hear it click. But before you do anything you should put some gauges on it and check the charge.


----------



## TorJoe (Feb 29, 2020)

Hi Raylo32,

Thank you for the prompt reply. Let me clarify:

I know the pulley doesn't move. From the videos I have seen on line, it is the clutch plate that should move to engage the spinning pulley, not the other way round. But for the clutch plate to be able to move towards the pulley, the clutch plate must have some axial 'play' to begin with (if it's completely fixed in position then it would not be able to move towards the pulley and engage with it). My question is: where is that 'play'? Right now I just don't see what would give that would allow the clutch to move (I mean move axially towards the pulley; I don't mean spin). Both the pulley and the clutch plate are fixed in position (axially speaking). Unless the shaft itself moves (axially) and drag the clutch plate towards the pulley, I just don't see how the clutch plate can touch and engage with the pulley. Yet, as I said, the shaft of my ac compressor does not budge (axially) no matter how hard I push against the clutch plate with my hand (with car the engine off). So where is the 'play'?


----------



## surferdude2 (Nov 21, 2019)

That clearance is normally supplied by shim washers in the hub of the clutch plate. You evidently left them out. Look inside the old hub or new ones should have come with the plate.


----------



## ukrkoz (Dec 31, 2010)

You are right. There should be manufacturer specified gap and clutch plate should move towards pulley body. Something is amiss during install.
https://ricksfreeautorepairadvice.com/car-ac-compressor-clutch/


----------



## TorJoe (Feb 29, 2020)

surferdude2 said:


> That clearance is normally supplied by shim washers in the hub of the clutch plate. You evidently left them out. Look inside the old hub or new ones should have come with the plate.


Hi,

I have not left out the shim washers. In any case, I am not saying that there is no air gap / clearance. I am saying I don't see how that clearance can be closed when the ac coil is activated if the clutch cannot move axially towards the pulley. The shim washers are just two pieces of doughnut-shape metal; they don't provide any 'play' like a spring does. 

For the clutch plate to be capable of being dragged towards the pulley by the electromagnetic force generated by the ac coil it must be able to move axially (i.e. towards the ac compressor). But if the clutch plate is completely fixed in position (axially speaking; it does spin), how can it move towards and engage with the pulley when the ac coil is activated?


----------



## TorJoe (Feb 29, 2020)

ukrkoz said:


> You are right. There should be manufacturer specified gap and clutch plate should move towards pulley body. Something is amiss during install.
> https://ricksfreeautorepairadvice.com/car-ac-compressor-clutch/


Hi,

Thanks for your reply.

I don't think I left out any parts. In fact to my understanding most (if not all) car ac compressors have exactly these parts: the compressor, the coil, the pulley, and the clutch plate (with shim washers inside).

I have no problem understanding why there is an air gap / a clearance between the pulley and the clutch plate when the two are not engaged. What I don't understand is how the gap can be closed when the ac coil is activated, given that clutch plate and the pulley both seem to me to be fixed in position (axially speaking). Where is that moving part that allows the clutch plate to move towards the pulley? 

Also, under normal circumstances, with the car engine off, if you push against the clutch plate by hand hard enough, should it move and touch the pulley like it would when the ac is running? Or should the clutch plate not budge (axially speaking) at all when the car engine is off and the ac is not running?

Incidentally, I have tried spinning the clutch plate by hand (with the car engine off) after bolting it to the shaft of the ac compressor. It's very stiff, but is capable of being turned. I have seen it mentioned online that it is normal to have resistance because the system is pressurized even when the car is not running. What I don't know is how much resistance is normal. But this is a different question from the one above. 

Thank you.


----------



## surferdude2 (Nov 21, 2019)

Here's a nice video that covers that and other facets as well.


----------



## TorJoe (Feb 29, 2020)

surferdude2 said:


> Here's a nice video that covers that and other facets as well.
> 
> https://www.youtube.com/watch?v=RFC5jMhUm4s


Hi Surferdude,

I had watched this video before but it does not really show me where the 'play' between the pulley and the clutch plate is. The guy supplied a 12 v to the coil and the clutch plate got dragged towards the pulley. Yes, it should do that. But when I actually take apart my pulley/clutch assembly, I don't see how the clutch should be able to move towards the pulley. As I said, both the clutch and the pulley are fixed in place axially. Where is the moving part here? Is it the shaft itself (to which the clutch plate is bolted) that gets pressed axially inwards when the ac coil is activated? As I said, I can't seem to make the shaft budge (axially) by pushing on the clutch plate by hand (when the car engine is off).


----------



## huesmann (Aug 18, 2011)

There should be a shim washer between the compressor shaft and the clutch. This provide the right amount of clearance to allow the pulley to spin when the clutch is disengaged. The washer needed can be different thicknesses, depending on the amount of friction material left on your clutch.

With the belt off the compressor, the pulley should spin freely with no voltage applied to the coil. When voltage is applied to the coil, the clutch is pulled towards the pulley, and they lock in place, causing the compressor shaft to spin.

If you have the belt off, no voltage, and the pulley doesn't spin freely, your shim washer is too thin, and the clutch is already in contact with the pulley. If you have the belt off, apply voltage, and the pulley still spins freely, the shim washer is too thick. You gotta be Goldilocks. :vs_laugh:

Here's a halfassed sketch. The green is the compressor shaft, blue is the pulley, red is the shim, grey is the clutch. The coil can only pull so hard, so if you imagine the shim being too thick, it won't have enough pull to get the clutch and pulley to meet up strongly enough. If the shim is to thin, the clutch and pulley could already be in contact, when you want them to spin separately.


----------



## TorJoe (Feb 29, 2020)

huesmann said:


> There should be a shim washer between the compressor shaft and the clutch. This provide the right amount of clearance to allow the pulley to spin when the clutch is disengaged. The washer needed can be different thicknesses, depending on the amount of friction material left on your clutch.
> 
> With the belt off the compressor, the pulley should spin freely with no voltage applied to the coil. When voltage is applied to the coil, the clutch is pulled towards the pulley, and they lock in place, causing the compressor shaft to spin.
> 
> If you have the belt off, no voltage, and the pulley doesn't spin freely, your shim washer is too thin, and the clutch is already in contact with the pulley. If you have the belt off, apply voltage, and the pulley still spins freely, the shim washer is too thick. You gotta be Goldilocks. :vs_laugh:


Hi Huesmann,

I completely get when you said - I really appreciate it! - but my question remains unanswered. 

I will zero in on one thing that you wrote: you said "When voltage is applied to the coil, the clutch is pulled towards the pulley." Now, for the clutch to be capable of being pulled towards the pulley, it has to be able to to move (if it's completely fixed in place how can it get pulled towards anything?). The thing is I do not see how the clutch plate can move at all, given that it is fixed in position axially. Something has to be able to move when the ac coil is activated so that the pulley and the clutch can touch and engage. The pulley is fixed in place (axially; it does spin). If the clutch plate is also fixed in place, how does it move to engage with the spinning pulley? 

The shim washers are pieces of doughnut-shape metal; they are not elastic like a spring. They don't provide any 'play' to the clutch plate; they are there to maintain the right air gap between the pulley and the clutch when the ac is turned off. So they can't explain how the air gap / clearance is closed when the ac coil is activated.


----------



## huesmann (Aug 18, 2011)

Sorry, I meant that the pulley gets pulled towards the clutch. The clutch doesn't move axially because it's bolted to the end of the compressor shaft.

Edit: actually, I'm not 100% sure what gets pulled towards what. I do know that the clearance is what's important, and that the clutch shim is how you adjust the clearance.


----------



## TorJoe (Feb 29, 2020)

huesmann said:


> Sorry, I meant that the pulley gets pulled towards the clutch. The clutch doesn't move axially because it's bolted to the end of the compressor shaft.


Hi again Huesmann,

My understanding is that the pulley is completely fixed in place. It does not move. It is the clutch plate that get pulled towards the pulley by the electromagnetic force exerted by the ac coil when it is activated. What I don't understand is how the clutch plate is able to move axially when it is, as your said, bolted to the shaft and there is no spring at the end the compressor shaft that provides play. The only way I can imagine the clutch moving is if the shaft itself moves, pulled inwards towards the compressor by the clutch which is in turn pulled by the electromagnetic force of the ac coil. But, as I said, if the shaft does have a little axial 'play,' a little room to move axially inwards towards to the compressor and outwards away from the compressor, shouldn't I be able to make it budge a little if I press on the clutch plate really hard by hand? Mine does not budge at all.


----------



## huesmann (Aug 18, 2011)

The outer part of the clutch should move. This image may help convey:


----------



## TorJoe (Feb 29, 2020)

huesmann said:


> The outer part of the clutch should move. This image may help convey:


Hi,

I think by the 'outer part' you mean the clutch plate. I do know that the clutch plate should move. I just don't see how it should be able to move if it is completely fixed in place axially. And if it is not fixed in place axially, shouldn't there be some play that I can detect? I can't detect any.


----------



## huesmann (Aug 18, 2011)

Dunno if you know anything about drivetrain clutches, but the pressure plate springs are really stiff—you couldn't move them by hand. Probably AC clutch springs (see the black springs around the edge of the disc?) are also strong. If you have a metal cup that's would fit on the plate around the spring, perhaps you could try using a C-clamp to press the plate in to see it move.


----------



## surferdude2 (Nov 21, 2019)

What you are failing to consider is that the clutch plate has separate internal parts. The actual drive portion of the plate is separate from the friction plate. The friction plate is mounted to the drive housing by springs. When the magnet is energized, the spring pressure is overcome and the friction plate moves into contact with the surface of the belt pulley.

Don't be concerned if you can't press on the clutch and make the pressure plate move. Those spring are very stiff and finger pressure won't budge them.

Of course, if you have insufficient shim washers on the shaft between the clutch and the shaft boss, the spring mounted friction plate will already be pressed against the belt pulley and it will seem to be unmovable. Test that possibility by removing the drive belt and verifying that the belt pully spins freely, as it should. If it doesn't, you need to install a thicker spacer on the shaft or more spacers. That assumes the belt pulley bearing isn't locked.

And to answer a question you asked earlier, it is difficult to turn the clutch plate by hand since the compressor turns with it and there is a high compression process taking place. It's akin to trying to turn and engine over by hand... even a small lawn mower engine is difficult to turn manually.


----------



## TorJoe (Feb 29, 2020)

surferdude2 said:


> What you are failing to consider is that the clutch plate has separate internal parts. The actual drive portion of the plate is separate from the friction plate. The friction plate is mounted to the drive housing by springs. When the magnet is energized, the spring pressure is overcome and the friction plate moves into contact with the surface of the belt pulley.
> 
> Don't be concerned if you can't press on the clutch and make the pressure plate move. Those spring are very stiff and finger pressure won't budge them.
> 
> ...


Hi surferdude and huesmann,

Thank you so much for both of your replies. I have looked at the clutch plate closely, looking for moving parts. It does not seem to have any separate internal parts. No spring, no moving parts at all. At least I can't see it. I can't see any gap anywhere that may provide play. Do all clutch plates have separate internal parts? 

I don't know how useful this is, but here's a picture:
https://www.walmart.ca/en/ip/Car-AC...-5L-DKS17D-6PK-OEM-92600JM01C/PRD7CXHV2QAEI92

Do some ac compressors have an internal spring that allows the shaft itself some axial play? 

In any case, I will try applying an external 12 V to the coil and see if the clutch budge. Thank you.


----------



## huesmann (Aug 18, 2011)

Your "spring" is actually that piece of rubber. It's bonded on one side to the "cup" that's riveted to the friction plate, and bonded on the other side to the "cup" that is bolted to the shaft.


----------



## surferdude2 (Nov 21, 2019)

They may not look like springs but all clutch pressure plates have springs in them. On a car, the pressure plate and the friction disk are separate parts. On an automobile a/c, they are made as one assembly.

No gap means you need more spacers or a thicker one on the shaft before mounting the clutch assembly.

The attached is typical for most American cars. Yours may be different but it still has a spring in it somewhere.


----------



## TorJoe (Feb 29, 2020)

huesmann said:


> Your "spring" is actually that piece of rubber. It's bonded on one side to the "cup" that's riveted to the friction plate, and bonded on the other side to the "cup" that is bolted to the shaft.


Hi again,

I have just looked at my retired clutch plate again, and compared it to my new clutch plate. I notice that a lot of the rubber between the various metal parts in the old clutch plate is shredded/melted. I wonder if this is normal wear and tear (it's a 2013 with 87000 miles), or if it is indicative of something more serious.

So my understanding of what you both are saying is that the rubber gets compressed when the electromagnetic force is exerted on it, and 'bounce' back when the force is gone, acting like a spring in this way.


----------



## huesmann (Aug 18, 2011)

No, the shredded rubber is not normal. I actually had a clutch with the bonded rubber that failed, so the outer part engaged the clutch, but the rotational force didn't get transmitted to the middle section, and thus did not spin the compressor.

Yes, the rubber acts like a spring just like that. Rubber does elastic deformation, just like a spring. Though it's not that it gets compressed, more like it undergoes tension from the plate being pulled to the pulley.


----------



## TorJoe (Feb 29, 2020)

huesmann said:


> No, the shredded rubber is not normal. I actually had a clutch with the bonded rubber that failed, so the outer part engaged the clutch, but the rotational force didn't get transmitted to the middle section, and thus did not spin the compressor.
> 
> Yes, the rubber acts like a spring just like that. Rubber does elastic deformation, just like a spring. Though it's not that it gets compressed, more like it undergoes tension from the plate being pulled to the pulley.


Hi Huesmann,

I mean if it is normal that after 87k miles some the rubber will show wear and tear and even some melting. 

What problems may these shredded/melted rubber indicate? 

Thank you.


----------



## huesmann (Aug 18, 2011)

IDK, other than substandard manufacturing.


----------

