POKO TD-169C Hair dryer circuit diagram
No your plan is not going to do what you want.  First of all the FR157 has a max reverse voltage of only 50V which is not sufficient for this use.  Secondly, and more important, the existing circuit uses the diode at a half-wave rectifier.  This cuts the power into the hair dryer in half when you switch it to &quot;low&quot;.  So the only two options are 100% power and 50% power.  Putting a different diode in place of the 1N5395 will get you back to the same place you started.