Volvo Repair: 1988 765 /turbo Wagon, resistor type, vacuum lines

Question
I have a 1988 765 Turbo Wagon with ACC.  The blower motor for the ACC became more and more "balky" at starting.  Finally it now attempts to start and fails.  The Green Snowflake Lamp for the A/C blinks.  I've removed and tested the motor(it functioned with 12VDC) and for a while would start with the fan switch set to 5, when that process finally failed I replaced motor believing that the motor simply had a starting problem.  Not the problem. New motor will not start either.  Motor gives off low hum, fan makes very small movement at starting and fails.  I now am convinced I have some type of relay/rheostat problem.  How can I test and resolve.  I have no idea where the relays and rheostats are located.

Answer
Michael, try this trick first.  where you see all the vacuum lines going into the control unit, try puttin a folded piece of cardboard in the slot so the connect doesnt move.  There is no way to test the power stage except by replacing it.  In the case there will be a stage and a connector.  That is the part, if you pull it out it will look like a green resistor type of thing.  Roger