I have a Cat 420D that’s not engaging the 4x4 off the switch. This machine is used on a ranch and doesn’t get run much so last year rats took up residence on top of the engine and managed to get into the console above the steering column and trashed the wire harnesses on top of the engine and the center console. We replaced the harnesses in the console and on top of the engine and moved the machine inside a shop. The 4x4 will not engage now, the switch no longer lights up and I found the P15 fuse was blown. Replaced the fuse and it’s popped again. Pulled the floor pan today and didn’t find any rodent damage on top of the transmission. I noticed the plug for the 4x4 switch is showing hot on all but the yellow jumper wire. Where is the coil for the 4x4 and what can I check?
The fact that a fuse is popping indicates a short to ground somewhere. It could even be prior to the switch. The attachment shows the location of all the solenoid valves on the trnamission including the AWD solenoid. Check your message inbox for an electrical schematic.