I know, it's an 8 year old thread, but if it helps anyone...
Having just been through the pain with my 2000 V70, I can confirm that the cause of failure is that the gaps in the motor commutator become clogged with conductive gunk, causing the motor to draw a large but useless current. Mine was trying to draw over 10A (!) and would have very quickly smoked if I'd let it.
With patience, it is possible to fix this problem. Opening the plastic case is the main obstacle - lots of gentle prising of the numerous plastic tabs. Remove the cover carefully and observe the placement of the 1cm square of thermistor material - it really does go in diagonally between the copper strips. The rest of the mechanism is fairly sane. The motor can be prised/knocked out. Opening the motor case requires bending the nasty little metal tabs back. Scrape out the gunk from the three grooves in the commutator and re-assemble. Once cleaned, my motor drew 0.3A free running and about 0.5A once fully re-assembled and driving the mechanism.
All this for a motor that must have cost pennies! TBH, were it not for the ugly holes in the bumper, I would be quite happy without headlight wash/wipe.
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