2014 Western Star 4900 - Fan Hub Won't Engage - AC Blowing Hot at Idle

Question

The engine fan on my Western Star isn't kicking on. It's fine when I'm on the highway, but as soon as I hit a town or traffic, the coolant temp shoots up to 215 and the AC starts blowing warm because there's no airflow across the condenser.

I've toggled the manual fan switch on the dash and nothing happens. I checked the fuses in the PDM and they are all good. I can spin the fan by hand when the engine is off (it has some resistance).

BackyardBilly · Accepted Answer

✅ Confirmed fix: The fan clutch solenoid valve had an internal electrical failure. It was receiving 12V from the ECM but the coil was open. Replaced the solenoid located on the driver-side frame rail. Fan now engages automatically with AC pressure and coolant temp.

TacomaTess · Answer

Most of these use a Horton air-engaged or spring-engaged hub. Check the fan solenoid on the firewall. If it's not sending air to the hub, the fan won't lock up. You can bypass the solenoid to see if the hub grabs.

2014 Western Star 4900 - Fan Hub Won't Engage - AC Blowing Hot at Idle

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