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