Volvo Repair: 2000 V70 power window, power window switch, window switches

Question
Volvo 2000 V70.  Power windows generally don't work. Problem started as intermittent and grew worse. Once in a while, when I first turn the key on, the windows will work.
  I see others have asked questions with the same basic similar problem. Sometimes the window goes down, won't return up. Otherwise, the driver-door window won't go up or down, and makes a buzzing or clicking sound when the switch is pressed to go down. When the problem is occuring, none of the four window switches work, either at the driver door or at the local door.
   When I push the switch to go down, I hear what is probably the relay in the switch assembly do a light buzzing or clicking.
   When the problem is not occuring, all the windows work normally.  
  I was able to take some battery cables and apply 12v directly to the driver-door window motor and the window raised back up normally and smoothly.
  In other postings, you have mentioned that this may also be caused by the power window relay.  Where is this relay? Is it part of the switch assembly that is behind the power window buttons? Or is it up in the engine compartment?
  As a do-it-yourselfer, I don't have access to a spare power-window-switch assembly. Based on your other posts, I strongly suspect that replacing the assembly will fix the problem.  The dealer wants $185 for a new one, and a local junk yard is going to have one available in a few days for $100.  Right now, I'm driving around with the door panel off, stored in the garage.  Before I pop $100-$200 for the part, I'd like to be confident that it will fix the problem.  

Answer
The relay for 2000 models is integrated in the drivers window switch.  If the problem is affecting all 4 windows when it happens, it is almost certainly the master widow switch.  $100 sounds high for a junkyard part.  It better come with some sort of warranty or otherwise I would look elsewhere for a used one.  I would feel confident replacing the switch but nothing is 100.  There is still the small chance of some sort of wiring problem causing it but those types of problems are very infrequent.

James