I drive and work on dump trucks mostly macks ive been having a problem with the fan clutches going bad . there air operated fans . ive tried changing the soleniod valves and everything but they just keep wearring out. About once a year i have to replace one. The cost to change the clutch is almost a thousand dollars and mack wont warranty this because were sitting on construction sites with the air running so the clutch just keeps kicking on and off . wearing itself out prematurely does any one have any sugestions for me. thanks