I have a friend that has a 1988 GMC 4x4 1500 auto. His 4x4 stopped working a while back and he replaced the thermal actuator with the upgrade and the "new" wiring harness. Not sure what made him start there but he did. I read yesterday the thread about the actuator on this forum and it was very helpful about making sure there is 12V at the plug that goes into the top of the tranfercase and the plug on the actuator and how to jump the plug if the ball switch is bad on the transfercase. Well, we are not getting power at the plug at the TC. I have a 1990 Chevy 4x4 1500 auto and everything on the truck is just about the same. We compared the fuse pannel and there are 3 differences, 1 being I have a fuse for 4WD at the pannel and he doesn't, 2 I have two places marked "power" and only 1 fuse pluged in and he has two fuses, 3 the he has a fuse marked "spedo" and mine says something else, can't remember this morning. Where is his fuse for 4WD????? We looked for another pannel under the hood but do not see one on either truck. After reading yesterday on here the problem may be power related because we are not getting power to the TC to send power to the actuator to engage it. He has 2 wires at the connector on the TC, a brown and a lt blue. The connector on the actuator has 3 wires, a brown a lt blue and a black. He spliced the brown from the new harness to the brown going to the TC switch. I'm hoping that one of you can assist us in telling us where the wires go from the TC back to the fuse and where the 4WD fuse is. If you need more info please ask and I will do my best to answer. Thanks a bunch!!!