It's a Kysor style. A couple months ago, I rebuilt it with a Kit Masters kit. Worked perfectly for months.
I ran the road engine during the night for A/C, and I flipped on the manual fan switch so I didn't have to hear it constantly engaging. Next morning, fan wouldn't turn off. Cycled A/C on and off, turned off engine, etc. With the manual fan switch, you could hear a squeak from the solenoid. Normally when I turn the engine off, the fan will freewheel for a few seconds before the solenoid exhausts the air, and it locks up. But now, it was shutting down locked up.
Now get this - normally if I try to spin the fan by hand, it will spin the pulley in the belt one way, and spin the engine the other way. This time it would spin the pulley one way, but the fan clutch would slip the other way.
Fast forward to today when I'm troubleshooting - solenoid works as intended with manual fan switch. I disconnected the air line to the fan and I can hear air leaking when it should be. I went to spin the fan and it freewheels both directions easily. WTF?!? Clutch lining already smoked? So I took it apart, and everything looks good. Lining doesn't look glazed or anything.
Here's the question - if the clutch did get worn out in a few months, what could cause it? Is it possible the solenoid under normal operating conditions isn't exhausting all the air when it's engaged and causing the fan clutch to slip when it's supposed to be locked in? Is that a thing? Because this time around I'm just going to replace the whole thing with a new one, and I don't want to have the same problem again in a couple months. Thanks.