2001 Ford Ranger Four wheel drive

For over a year now my 4 wheel drive will not work. The drive motor and actuator on that motor have been disassembled and reassembled and all is in order, clean and greased. With direct battery current it operates properly. All fuses are okay and are not blown, nor have they ever been. The dash switch has been replaced with new factory replacement, thinking that was the problem. The switch does not light up when turned to 4 wheel drive and the actuator mounted on the transmission/transfer case does not receive power. The truck was recently in for the wiring harness change (factory warranty/recall job). My cousin owns a ranger with the same exact problem. I am reluctant to take it to a dealer fearing that they will issue a large bill for a simple fix. Our two rangers have experienced no collisions and have no damage. We wondered if it might be a warranty/factory recall situation. Hope you can help.