Volvo Repair: 1992 740 a/c and fan switch, vacuum source, frustration level

Question
My fan blower only works on the highest speed 5.  I have read
the resistor must be replaced.  Where is it located, where do I
get the part online?  Would this problem cause the a/c
compressor not to come on since it is connected also to the fan
switch.  I am a do it myselfer.  Can you help me?  Thank you.  
Steve

Answer
  Steve...Steve...Steve
         Wow...your frustration level has been maxed out for too long...these problems are the worst..ya gotta make SUPER DUPER SURE that you have good vacuum source to switch...it uses the switch to do lots of work...beside opening and closing little air vent doors as well as controling the A/C....make sure you have full charge of 134a...some systems won't operate with lo or no charge...another consideration...take jumber wire from pos.on batt...find hot input in a/c unit...touch a/c input wire...if it works the unit is ok....see if it gets cold...be ready to pull jumber wire if bad noises occur...not a good sign.
look online ...where finding parts is easy...just type in your needs...it's amazing.

     Best Wishes,

           Bilbo