Since I'm changing the headlight assemblies to projectors it was simple to remove the driver's side headlight wiper moter.

The toothed rod which moves eccentrically on a gear had slipped off the gear.

Seems that somehow there was some fore and after play on the wiper shaft (to which the gear is attached) and the toothed rod wobbled off.

It may be that the plastic back plate is the problem. It is held to the case with plastic prongs; the kind to open up by using a screwdriver to pry out.

Some of the prongs are broken or worn at the end where they catch the case. I can't get it as tight as it could be.

So the backplate may be loose. The plastic is a bit soft for what it needs to do. It seems a little warped.

With the backplate off, you can push the wiper shaft out the rear of the case a little and easily re-fit the toothed rod to the gear.

Can you buy just the backplate as a replacement part?

The case is an odd rounded shape; don't see a good way to tighten the back plate using a hose clamp etc.

 

To follow up -- that was not the only problem. I had to remove the inner plate, the big gear, and the little white gear and then bend the metal "flipper" electrical contact so it was once again tight. Then the little white gear could make the contact click.

Instructions w/ photos at:
volvoforums.org.uk
Headlamp Wiper Motor Repair

http://www.volvoforums.org.uk/showthread.php?t=51146