Do I need to replace the 4 wheel drive switch?

When I press the Automatic 4 wheel drive it, the light flashes but nothing
happens. Same thing happens when I press the 4-high button.  However,
when I press the 4-low button I hear the front wheels try to engage but it
doesn't actually go into 4 wheel drive.  I also hear it disengage when I put it
back in 2 wheel drive.  I tested the switch and it all tested good except for the
4-high button.  Do I need to replace the entire switch?  Suggestions??