Volvo Maintenance Hints for 7xx/9xx - Bill Garland's Nuclear ...

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Electrical Diagnostics:
Start the engine.
Disconnect quick connector at air control valve.
Test for battery voltage on the middle pin (it is pin number 2 "GREEN wire" if
you slide the rubber off), you should detect 12V or so (with engine running).
Turn off the engine.
Test for ohms on IAC between middle pin and any side ones, you should have
between 6 and 20 ohms in each case depending on the model. If you do have
this resistance, then it means that the motor of the IAC is good. If not, don't give
up yet.
Disconnect the hoses from the manifold and the intake hose, disconnect the 3pin
electrical connector, loosen the top nut on the band clamp around the valve
body, then remove the valve. Off the car, look down the bore of the valve, and
then by supplying the center pin with 12V and shorting either of the outside pins
to ground, the "door" should fully open or fully close.
Disassembling and Cleaning the Valve
Clean the slip ring (the one wherein the brushes are touching) inside the IAC by
taking the IAC apart. [Editor's note: this is not possible on newer IACs with no
housing clips.)
Before you take it apart, mark the housing (a pen mark or screwdriver will do)
so you can assemble it in the same position. IT IS IMPORTANT!
With a small screwdriver pry up the clips or crimps which are holding the
housing (there are four of them). Once they are up, pry on the housing a bit and
the whole thing should come out. At this point, you will encounter a bit of
resistance because of the strong magnet inside, but there is nothing to worry
about, just keep going until everything comes out. Be careful not to lose the oring
or the small cone piece -- which will probably fall off the armature shaft and
be laying at the bottom of the barrel with the permanent magnets and the wiper
contacts. You MUST NOT try to push it in once you started separating the
housing (or you will destroy the brushes inside the valve). Once you open it, you