1999 Chevrolet Blazer LS 4X4 Problems

I had to have the 4 wheel drive actuator replaced on my '99 to resolve a similar issue, I had 2hi, but no 4hi, when you pushed the button for 4hi, the light by the switch would either flash between lo and hi 4wheel then jump back up to 2hi or when selecting 4lo the light would go out. The actuator wasn't locking onto proper position, I try to always shift it now with the trans in neutral, then drop in down into gear, I dont think the unit survives shifting on the fly well.

The Chevrolet Blazer wont shift into 4LO at speeds greater than 3mph because of the dangers of shifting into such an extreme gear ratio at speed.

You will need: small screwdriver, q-tips, and rubbing alcohol.
Pop out the 4WD button assembly from the dash. Unplug the the two wire connectors. Hold the button assembly in your hand face down. Make sure you are in a place that, if you were to drop something small you can find it easily, but lets just hope you're careful. With a small screwdriver, pry the back of the assembly from the front. Remember to keep the face down in your hands at all times. You see those blue boots with metal contacts on them? These are the things that will fall out easily. Take your time, remember where these boots are located they will pop out easily. In fact, have someone handy with a camera to take a picture of it before going further. Now with a q-tip dipped in alcohol gently clean the metal contacts in the blue boots. Then, with the q-tip and alcohol, clean the whole face of the board that the blue boots come in contact with, paying close attention to the white circle patterns on the board. They may not look dirty but it doesnt take much to make this assembly act nutty. When done cleaning and parts a fully dry, re-assemble and give it a try.