".....That motor is a puzzle, if its a dc motor why would it have 3 brush
es. I have only seen 2 or 4 on dc motors......"
From the excellent Workshop Practice series No.16 - Electric Motors - Jim Cox:
"...More modern types (of automobile wiper motors
) are permanent magnet motors which use a three brush
system. A pair of brush
es in the normal position 180 deg apart is used for low-speed operation. One of the low speed brush
es and a third brush
set at about 120deg are used for the high-speed wipe. Because the brush
at 120 deg only sees a fraction of the normal motor back EMF more current flows and the motor runs proportionately faster...."