Well I managed to get over to the local pick n pull this weekend to snag myself one of the Volvo actuators and I can confirm they work as described. I checked the movement of the butterfly actuator with my head in the engine bay and by the seat of my pants on a test drive. I neglected to use any of the factory delay valves so the changeover is quite noticeable.
the diagrams provided here were not appropriate for my unit. First, the ports of my unit are the reverse of the description. The black nipple is the vacuum port and the white nipple is the pump outlet.
Second, I had to wire mine up differently. If the other units people have are at all the same internally then wiring it up according to Method 3 will not work. Here's a shot of the guts of my unit (you can pop the lid off by hand, it just snaps into place):
The numbers 1 to 3 on the above image correspond to the pins on underside of the unit, where the harness plugs in.
Pin 1 is connected to the positive (+) lead of the electric motor as well as one lead for the solenoid coil.
Pin 2 is connected to the ground (-) lead of the electric motor
Pin 3 is connected to the ground (-) lead for the solenoid
The short rubber vacuum line coming off the side of the black (vacuum) port connects to a nipple on the underside of the solenoid. The solenoid itself actuates a small trap door with a rubber plug on its underside. When energized, the solenoid snaps the trap door closed, sealing the end of the vacuum line and forcing the pump to pull vacuum solely through the main port. When the solenoid is de-energized it releases the trap door and "vents" the vacuum.
When wiring the unit according to this thread (12 volt power applied to pin 3) the electric motor does not engage, only the solenoid will actuate when you ground the appropriate pin.
Here's what I did:
Attention: The below quote block describes my first attempt at wiring the pump up: This method will NOT work.
Now, the CORRECT method can be even simpler than the above:
You can mostly use the original diagram for wiring up your relay, but ignore Pin 87a.
Switched 12-volt power should be connected to Pin 1 on the pump.
Pins 2 and 3 on the pump are grounded through Pin 87 on the relay (the Normally Open circuit).
Now, when you turn your key to Run your ECU grounds the butterfly control circuit with your switched power, this energizes the relay, grounding the pump and solenoid through the normally open circuit (87). The pump engages and the solenoid snaps closed, applying vacuum to your butterfly actuator, closing the butterflies. Then, when the ECU opens the butterfly control circuit your relay flips back over to the normally closed (87a) circuit, the electric motor shuts off and the solenoid releases, venting the vacuum and allowing the butterflies to open.
That's it! Took me a while to figure out why my pump wasn't turning on, hopefully I can save others the same headache. This retrofit is well worth it in my opinion. I love that I've been able to get rid of that nest of 20-year old vacuum lines. Thanks to the original poster for making us aware of this option!
Switched 12-volt power is still connected to Pin 1 on the pump.
Constant ground is connected to Pin 2 on the pump.
The ECU butterfly control wire (Grey wire from the OEM butterfly solenoid plug) is connected to Pin 3 on the pump.
So, when you start the car your switched 12-volt power kicks the pump on. When wired this way, as long as the key is in Run position, the pump motor will function.
Now for the fun part: Your ECU controls the amount of vacuum "seen" by the butterfly actuator by changing the solenoid's duty cycle.
It does this by rapidly closing and opening it's ground circuit (grey wire) to achieve a specified pressure at the butterfly actuator by opening and closing the trap door inside the vacuum pump, much like an electronic boost controller controls how much pressure your wastegate sees. Essentially, they "vent" pressure in short bursts to control the actuator diaphragms.
Anyway, sorry for the confusion everybody. I was so eager to share my knowledge with the internets that I posted my method without properly testing first. My downfall was that my first test drive was on a warm engine; this morning on my drive to work the engine was a complete dog until it was up to temp, which was my first clue (apparently the butterflies are extremely important for proper combustion on a cold engine). Then this afternoon I remembered the below image, B02-1000, and it hit me:
My Katakana isn't very good, but one of those words is "Shiorenoido," which means the vertical axis MUST represent Duty Cycle. (I later confirmed visually that the solenoid in the vacuum pump is energized 100% of the time at idle, for what it's worth.)
I have tested this setup thoroughly tonight, even going so far as to change the opening point through Nistune. The above image has an analogous table in the ECU ROM, making the butterflies extremely tuneable. I shifted the dropoff point from 2000rpm to ~4500rpm and it works spectacularly! I have yet to experiment with this fully but it appears to me that, without the factory delay valve in place, you should be able to precisely control the "ramp" of the butterfly opening action by changing the shape of the graph above in the ECU. Exciting stuff for me and my TD06!
Here's a pic of the unit for part# reference:
**Edited for bungled wiring logic.