The differential is not engaging and the light on the floor board does not come on when I shift into 4WD on my 1989 silverado. There are two sets of wiring harnesses going into the differential. The upper has 3 wires and the one on the bottom has 2. I checked the fuse and its fine. Do both sets of wires go to solonoids inside the differential?

 

The 2 wire connection is power to the actuator, the 3 wire goes to a contact switch that turns the light on. Check for power on the 2 wire when you have it shifted into 4wd, remember to drive a little after you shift to give it a chance to engage.

 

Had the same problem on my '95 Z71. Had to replace the actuator wire harness. Hope this helps.

 

I just had the same thing happen to my 88 and had to replace the actuator. The light in the cab can take up to 30 seconds to kick on so be patient

 

yea im having the same issue with my 95 z71. the light in the cab comes on when i put it in 4low and 4high, but only 4 high works. pretty sure its the actuator.

 

'88 1500 4 wd pickup. New actuator, still no 4wd. Is there or where is the fuse located?