Blower Motor - Not working on High

The blower motor has no power when the selector is set to high.  It works fine
on levels 1, 2, 3.  Power seems to drop both to the fan and AC switch when
set to high.  I have checked fuses, replaced the resistor, and I have replaced
the relay with no effect.  I am looking to find the next logical point of possible
failure.

I am competent on all aspects of working on mechanical issues but I have no
expertise on how to measure/diagnose electrical issues - but I can easily
follow instructions.

My next steps would be to pull the selector switch to make sure there are no
shorts or dirty contacts?  

I have no history with the car - I just purchased it for my son and discovered
the issue.