Engine fan wont turn off

[davidjurss]

Having a bit of an issue here lately, and I'm tired of just throwing parts at it. I have an 06 CM870 that the engine fan has stayed on and wont turn off. I went after the usual suspects, like the air solenoid and ac high pressure switch to no avail. I've even replaced the dash switch, with no results. The fan will free spin when the truck is started, but something is commanding the solenoid to release air and start the fan, so I'm fairly certain the fan hub itself is still good. I dont have Insite yet, so I can't check to see what's going on internally, but so far it hasn't kicked on a check engine light. Any help would be appreciated, since this is killing my fuel mileage and with a Peterbilt 379, I need all I can get! Thanks!