Researched this plenty this week and found this. Credit to Grube. Post is below in similar posts.
Well, finally got some time to address my 4wd actuator on front axle. Went ahead and ordered the upgrade kit from old Thermal to newer style. Used Dorman 600-600 harness and Dorman 600-601 actuator. Removed thermal actuator, cleaned threads, installed new spacer plug. Applied threadseal to new...
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“Removed thermal actuator, cleaned threads, installed new spacer plug. Applied threadseal to new actuator and wind into housing and tightened. Went to plug the "plug and play" harness in, and the 2-pin plug that connected the old actuator was a different style. So I had to cut the plug pigtail off the old actuator, cut the plug end off the new harness, and splice the old pigtail onto the new harness with dual wall heat shrink connectors. After confirming the Blue wire was indeed power, and black was ground. The brown wire they suggest to run to 4-pin plug on top of tcase. Looked like P.I.T.A. to get at, so I ran the brown wire up to engine bay, over to driver side along top of firewall and through firewall under brake booster (hole drilled, rubber grommet installed). Once in cab, had to lengthen wire 10" (used red as I had no brown), and attached to the rightmost pin on the DRK GRN labelled connector under dash. This pin is powered by the 4WD 25amp fuse, and is key-on switched power.”
