Non D - AC Clutch question

[Dangermouse]

07 F150 truck with 87k

3 weeks ago I notice an odd sound from under the hood when I start up that went away when warm. I couldn't see anything obvious. 2 weeks ago I notice a burning smell and discover the s-belt rubbing on a non-turning AC pulley. (of note, the AC was still blowing cold). Dissection shows the pulley bearing disintegrated and coil damaged. My working hypothesis is that the heat generated by the failed bearing melted the insulation around the coil wiring.

I buy new components and reassemble. First on goes the coil. Next is the pulley and I note that it turns freely. Lastly goes on the hub (which I reused as it seemed OK) that bolts to the shaft of the compressor. Once I bolt it on, I notice that the pulley no longer turns. I recall the warning about recovering the shims. I take them out of the old hub and insert in the new. The pulley now turns though I can hear/feel a little friction but I think maybe that's a rough spot that will bed in.

After putting on the belt I start her up and the pulley seems to turn freely. What I should have done is let it sit for 5 minutes, but I am impatient and push the aircon button. Things go south quickly and the pulley is no longer turning; burning belt smell again.

Disassemble and find that the pulley bearing is locked and shows signs of heat around it. Was running for about 2-3 minutes

What's going on?

Option 1 - dodgy bearing in new pulley - possible but unlikely
Option 2 - too many shims in hub - would cause compressor not to become engaged presumably, so wouldn't result in this failure
Option 3 - too few shims in hub - what would happen then? Where is the the take up in the system? When the coil is energised does the hub move to come in contact with the pull, which must mean that there is play in the compressor shaft
Option 4 - seized compressor - subsequently tested and it turns freely by hand
Option 5 - reuse of the hub was a mistake for some reason. There is no friction material on the replacement one I bought, just scored metal, so I cleaned up the original.


any advise appreciated

[Ron]

I don't understand how it could cool with a non-turning pulley (on the compressor).

Best guess- The outer clutch plate is spring loaded and the coil pulls the plate into the mating surface on the pully/hub, which is connected to the shaft...
You usually have to add or remove shims to obtain the required gap between the outer plate and mating surface of 0.014"- 0.030", at rest.

-Race cracked installing bearing (if press/tap-on type).

-Compressor locking down (intermittently).
??

Got a pic of the damage?

[Dangermouse]

I’ll post some tomorrow.

So is there no play (axially) in the compressor shaft and all the play is in the springs in the hub?

As I reused the old hub I wonder if the springs in that are weak/damaged.

[Dangermouse]

I think the before and after pictures are self explanatory

To be clear, Ron, in the original failure, the pulley was turning but very slowly, certainly much less than the belt running over it, so it may just have slowed down and I was feeling the residue of the blower blowing air over the coil and the coil still being cold.

With the damaged pulley, when I took the clutch hub off there was only half of the retaining snap ring present, which may have allowed the pulley to move slightly on the shaft. I found the other half in the hub last night in between the inner and outer rings which might have interfered with the spring operation.

[Ron]

Correct, the shaft rotates only.
Unless they got VERY hot, I doubt the springs are weak...fwiw, their job is to disengage. (Other damage should be obvious, causing the plate gap to be uneven).

====

It's common for the replacement parts to look different, but the difference in plate diameter bugs me since there are scars on the coil and you are mixing old\new sets....
There were 2 snap rings correct? (Loose coil pulled itself out of position??)

57516

[Dangermouse]

Yes, the snap ring for the coil was firmly in place. No movement there.

I used new coil, new pulley and old hub, partially as you note, the one NAPA gave me had a smaller diameter and didn't completely cover the (what I assume is) friction material on the pulley.



The key question for me is - if a compressor turns fine manually is it still possible for it to be seized when under load.

If I take it to a shop I know they will tell me its the compressor. I'm debating getting another pulley and paying closer attention to the airgap and shims but that's $80 wasted if it is in fact the compressor




(a side gripe is that nowhere in metro ATL carries any of these three parts in stock. Hard to believe for a vehicle that is the best seller every year for 20+ years)

[David T]

This is exactly why most shops won't F--K around with this. A compressor is not all that expensive and in most cases, if the clutch is bad it is because the compressor went bad. Look up Four Seasons.

[Ron]

The key question for me is - if a compressor turns fine manually is it still possible for it to be seized when under load.

If I take it to a shop I know they will tell me its the compressor. I'm debating getting another pulley and paying closer attention to the airgap and shims but that's $80 wasted if it is in fact the compressorAn internal part or a blockage (upstream of any shutoff/safety) in the high side could seize the compressor...
I would call (not go to) NAPA and mention the "undersize" diameter and if there are two styles (...and nothing else). If not, put what you have together with less shims (even if none). That will force it to be engaged. Confirm it does. Then check that you can turn the shaft and all by hand w/o any binding or odd sounds, using the pulley. Then install the belt, start the engine and see what it does. Watch the low side pressure -- Shut it off when it drops to ~30 psi, and back on at ~70 psi. OR, if you have a manifold set, watch the high side and don't let it go past ~225 psi. If it acts OK for several cycles (manually), the compressor is probably OK. From there you will know whether it is a good idea to demand a refund...but settle for the "correct" part.

Watch out for flying parts and refrigerant!


(a side gripe is that nowhere in metro ATL carries any of these three parts in stock. Hard to believe for a vehicle that is the best seller every year for 20+ years)Yeah. For a long time the clutch set cost more than the compressor, complete with clutch, for most applications. They figured most consumers would choose the latter route to avoid evacuating and recharging the system (and have it all new). [Censored] were right, and, of course the repair shops never complained...
Not to mention the dealers; Who don't have to store parts information etc., for vehicles over 10 years old..

============


This is exactly why most shops won't F--K around with this. A compressor is not all that expensive and in most cases, if the clutch is bad it is because the compressor went bad. Look up Four Seasons.
+1

...Yeah, I agree...If a friction plate surface is toast, either the compressor was seizing, or the plates have seen too many cycles. But fwiw, for most bad clutches I've seen, the coil or bearing failed first. (Many sold only as a set.) If a system was performing well and anything in the set failed, I would consider how hard it is to get at the compressor v/s the expense of the compressor along with other parts required to maintain its warranty...
If mine has a fried plate, no one cares if I tack it down, $o I'm gonna' "F--K" with it! :biggrin:

[Dangermouse]

So what happens when a compressor seizes?

Does the belt just burn off or do you get bearing damage to the pulley? Or both?





I am hanging my hat on the suspicion that I could (in retrospect) hear the pulley bearing growling for a week or so beforehand.

[Ron]

So what happens when a compressor seizes?

Does the belt just burn off or do you get bearing damage to the pulley? Or both?
Usually, only the belt fries.
If the compressor seizes, the belt, drive/clutch pulley, or friction plate surface(s) can fry.
The bearing is relatively very tough. It should take any heat involved -- age and foreign objects are its worst enemy (e.g., loose snap-ring ;-).
If the pulley-hub bearing seizes, the belt, pulleys, or even one of the surfaces holding a bearing race (compressor snout/pulley-hub) can fry.
In either case, the belt is usually the only victim, unless it is of 'high quality' and has a tensioner...

[Dangermouse]

A compressor is not all that expensive

Here's why I am F ing around with this.

Call into my local shop for a quote:

Compressor - $450
Labor - 1 Hr - $130
Evac & Refil - $175

Tot - $800 inc tax and shop supplies.

Plus no warranty unless I change out dryer and orifice tube - another $500

Plus a tow to get it down there - $?

[David T]

The reality is you probably need all of that to fix it right. After you play with it and spend your time and money you will probably be doing exactly what the local shop is saying. They have seen a whole lot more of these than you or we have and they know how this story ends already.

[Dangermouse]

You’re probably right David but I’m willing to investigate it a bit, understand what is happening and risk another $80 before just handing them about a third of what the truck is worth.

[David T]

One way to keep the costs down, if the shop is willing to work with you, have them remove the refrigerant, you get the parts and you do all of the R & R of the parts. Then let the shop do the evacuation and refill. If the vehicle is worth that little maybe you should forget about cold air? Because the compressor is the most expensive item maybe get a price to have it checked out and repaired. Contact Classic Air in Florida.

[DMC5180]

Dermot,

Which engine do you have?

V6 4.2L
V8 4.6L
V8 5.4L


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[Dangermouse]

Sadly the V6

[DMC5180]

Sadly the V6

The kit from rockauto gives you everything you need to DIY. Have your local A/C shop evacuate the system, get credit for refrigerant removed then take it home and swap the parts. Go back to the shop for a System fill. You should be able do it all for about $400 total.


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[Dangermouse]

Thanks. Somehow I missed that when browsing the RA site

That will be plan B, as at the moment I can't drive it to get it evacuated without a pulley, which arrived yesterday, so I just need time to fit it.

I will test as outlined by Ron above, and if compressor bad then I will get it evacuated and get this kit.