I recently rebuilt a wiring harness on a 760 turbo and bought a computer.
the car still will not start. what I need to know is if there is a check with a multimeter for the power stage to see if it is still operational.
if not will the powerstage from a 240 work?
any and all suggestions will be appreciated

I know this test works on an 89 700. I'm not positive 85 is the same. I don't know of a test for the part, but I this is what you should see @ the harness going into it. If everything checks out @ that point, it makes the power stage te next likely suspect
Pin 2 should be ground
pin 3 should be connected to the shield on the wire going to #5
Pin 4 should have 12 volts with the ignition on, no less than 10.5 when the engine is cranking,
Pin 5 should bounce between 0 and 2 volts when the motor is turned over (helps to have an analog meter to check this)
Check the part # to verify compatibility. I know on later cars (like 89 or so) the power stage is the same part used on all kinds of euro cars. porche, saab, citroen, etc, so it's a pretty common part.

My Haynes manual is out of town, I think that the information you seek is in it, perhaps someone can help you.

I checked a Chilton manual that I keep around in case I run out of toilet paper, but it was of no use.

If it is like the one I tried to test, there are four wires and a ground. You could compare their resistance to ground looking for a difference. I think that the resistance is low, like 5 to 15 ohms.

I had a problem with my 1990 744 Turbo and the culprit was a bad connection in the plug. The technician cleaned the terminals, added dielectric grease and zip-tied the plug together. There is also a ground to the body I think, but I had already cleaned that, (Cleaning, dielectric grease, and a zip tie is a common repair for old Volvo connectors - the technician gave me a tube of grease and told me to do any connectors that I could!)
--
3 8s & 2 7s 725,000 miles total

Actually the haynes manual is pretty useless beyond a Wiring diagram.
it pretty much says "if you don't have spark and the battery works goto a Volvo dealer"
I measured the resistance and most of the pins measure 5 Meg Ohms which to me means "a lot of circuitry" or the power stage is bad. but I have no known good module to test. but if I had a good module I'd not be asking this question :)