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

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will understand why.
You will then see oil and crud all over the armature and the commutator. Clean
it up with brake cleaner and carefully flush away all crud especially from gaps in
commutator.
Clean the contact points with very fine emery cloth or a Scotchbrite pad and
polish them. Be careful; don't bend anything. Again, make sure you don't lose
the little cone piece. You'll need to get it out of the barrel for re-assembly - it will
come out easily but you have to use something non-metallic because of the
strong magnets around the housing.
When everything is spotless and oil free, put the cone on the end of the
armature shaft, so that it tapers away from the armature. The cone is important,
because it acts as a ramp when you replace the armature, gradually spreading
the wipers so they land on the commutator without bending them out of
contact. Also, a little silicone grease on the o-ring seal can't hurt. Once you
take it out, slide it over the shaft and keep it in the upward position (so it won't
fall off) while assembling it.
To re-assemble, put the tee upside-down on the workbench, with the cone in
place, and gradually feed the barrel down. It's a bit of a trick to keep it straight,
because the permanent magnets have a habit of sucking the armature from
side-to-side. It doesn't take much force. Once the armature is seated properly,
re-align the marks on the barrel and tee by simply twisting the tee relative to the
barrel. If you forget this step, the valve may likely not open or close fully. After
doing so, then you are done. Push back the clips (if you have clips, and don't
use a hammer)
Re-test the valve as above with test leads before the final crimping. Mine
worked fine now, fully open, fully closed. I then squeezed the crimp tabs back
into place with large channelock-type pliers, and double-checked the alignment
marks. Replace the valve, making sure the flow arrow on the tee points in the
proper direction. The arrow should point TO the intake, FROM the main throttle
inlet hose. Tighten the hose clamps, and viola! "New" IAC valve. The entire
procedure, including the pulling of the valve out and installing it back takes
about 30--45 minutes. Test the side pins for ohms and re-install the IAC. You
should now have a fast idle. Oh, make sure your PRM at idle is about 800 rpm.
PS: I drilled and put in a small screw to prevent housing from rotating.
[Another Tale of IAC Repair:] The following Idle Air Control Valve repair might be of
interest to fellow tightwads who experience a HIGH idle problem. I removed the bad