Fan clutch or hub

[JimT]

Been nice and busy lately, had a good run without issues until yesterday. Driving down the road started to smell a faint wiff of burning/melting plastic. Was about 95 outside and I had the AC going for the past 4 hours of driving. Not long after, during some stop and go driving, I noticed the engine fan WASN'T kicking on every time I came to a stop (as it typically does when I have the AC on). Just as I get back on the highway I hear the fan finally kick on... And stay on. Then I noticed the air compressor kept kicking off. Quickly realized secondary tank was dropping pressure.

Got pulled over and determined that the air was coming out of the fan clutch or hub. Hard to tell which with the engine running and the pressure drops below the switch cut off too fast once the engine is shut down.

This fan clutch was replaced a few months ago, by me. The clutch itself is holding just fine. I did notice some kind of oil or grease or something had seeped out from the clutch onto the new fan blade, likely the cause of the smell.

Anyway, was pretty close to the house when it happened so I cancelled the rest of my loads for the week and brought it home with the fan running and air leaking. Did some prep disassembly last night and will be diving in to it shortly to try to figure out the problem. Was wondering if anyone on here has any insight. Is this a failed seal? Bad part? Did I screw up the installation last time? Or could this be a problem with the hub itself? How about the pressure switch, it was backordered until recently so I have a new one to throw on. Could it have been applying the wrong air pressure leading to overheating and subsequent melting inside the clutch? I want to understand the root cause here before swapping out parts.

One other thing. Not long after the fan clutch was replaced we had a 100 degree day. At one point during that day I had smelled the same plastic/burning smell. At that time I also noticed a little seepage around the clutch and onto the fan blades. It didn't continue and at the time I figured it was just a little grease seeping out on a hot day. Months went by without further issue, even with heavy AC usage.