98 series 60 12.7 engine fan Horton clutch?

Is the fan solenoid also cycling? Sounds like intermittent ignition power loss. I think you're just seeing a symptom of a loose ground or pos wire in the battery box.

I'd also look at fan relay. It could be shorting out.

Check all cables and pay particular attention to the small wires in the battery box. Don't just look. Take apart, inspect, clean, tighten.

 

I would doubt very seriously if the hub was bad. Very simple arrangement and if it operates and doesn’t leak air it should be ok. I would check my wiring and or connections on my a/c fan switch on the dryer. We used to could test a fan operation by either unplugging the switch, or shorting across it with a paper clip or such. Just depended on how the ins and outs were set in the ECM as to which way would work. So……. It could actually be shorting to voltage, or operating when circuit is open just depends. Just a thought.

 

Had a similar issue with a M2 and it was the plug at the solenoid. Replaced pigtail and all good.

 

Evidently the clutch is working. This issue is, what is signaling the clutch to engage/disengage? That is the issue. If the clutch was not working, it would be engaged full time.

 

Very well could be a grounding issue. It was for me.

 

It's supposed to come from ECM, however things happen and stuff breaks, which can make it very difficult to find the ground problem.
I ended up bypassing the ECM all together. I ran a new ground to my solenoid.

My fan is engaged whenever my solenoid is OFF. So for me a bad ground meant that my fan ran continuously.
I had to run jumper wires to the solenoid plug to confirm my problem before I cut wires and made stuff permanent. But now I have a fan that runs and shuts off correctly, without my ECM.