MODULE-BASE 3973452 - Caterpillar

(5KJ, 3ZJ, 4CK, 8PN),
3406E (5EK) Truck EnginesThe Horton Diesltemp Air Operated Fan Clutch is an OEM option that can be ordered on the above engines. After April 7, 1995, The Horton Diesltemp Air Operated Fan Clutch has a patented "System Sentry," which consists of a plug that melts when the engine overheats. The plug, which is located on the outer surface of the piston friction disc, acts as a thermal fuse. If the fan clutch slips, heat will build up at the outer edge of the piston friction disc and work its way toward the center of the fan clutch. When sufficient levels of heat reach the "System Sentry," the center of the plug melts. This allows air pressure in the fan clutch to drop, disengaging the fan clutch immediately. This air leak will not significantly impact the rest of the vehicle air system.
The defective fan clutch can be detected by the sound of air being released after the engine is shut down.
Do not replace electronic parts, hoping to solve the engine overheating problem. For more troubleshooting information, Reference: Horton Industries, Inc, form numbers L-22459-A-0595 and L-22537-0795IP, available from Horton Industries Inc. Phone 1-800-621-1320.