Replacing the Marelli wiper motor with a Bosch motor
The wiper I got was described on ebay as for a VW Rabbit, Cabriolet,
Jetta 77- 84, Bosch number 039 024 1058.
The motor has the 5 wires and the bent tab that James Seabolt refers
to in his guide.
I have it working with 3 wires right now to get low and high
speeds and no parking capability. I will get to the electrical later but now
will discuss the physical aspects of this mod. I'm not sure if I have a different
motor or if the Pininfarina is different underneath that cowl, or both, but
I had significantly more to do to get this motor in there.
First, the bolt pattern is the same, sort of, same spacing
but upside down. The 3 raised points that mount to the wiper frame or chassis
are a different outer diameter. The original mounts are of a diameter that allows
them to slide through rubber grommets in the chassis. The Bosch assembly mounts
are too large for this. So I had to remove the grommets. This also mounts such
that the motor extends to the outboard side as opposed to the inboard which
is the way the Marelli mounted.
Next, the mounts are too long so that when mounted with bolts
seated, the bolt heads interfere with (as in block) the first link to the wiper
assembly. To correct this, I cut 1/4" off of the mounts. This allows the motor
to mount closer to the chassis and the shaft to stick through further. This
then allows full motion of that first link. A few things to be mindful of here.
The more you cut off those mounts, the less threaded material there is for the
bolt to hang on to. If you cut too much off, the motor itself will be in contact
with the chassis and this you probably do not want. There is one other point
and I will get to this further down**. The following shot is before I cut the
mounts so you can see how low the shaft is.
To actually mount it, I used a flat washer on the mount, then
the chassis, then another flat washer, lock washer and bolt, with threadsealer.
The wiring appears to be quite different in the Pinin and I
haven't found a diagram for it yet. There are only five wires, 1 pair is blue/white
and blue/red, the other pair is something/something and gray/yellow, and the
fifth wire is black/purple which appears to be ground. So far, I have used the
second pair for high and low speed positives. I haven't been able to make the
park mechanism work yet, but it is at this stage that you would establish the
Now, here is the other point** I was referring to. The fact
that the motor now comes off the assembly in the opposite direction causes interference
with the pan under the cowl. The less you cut off the mounts, the more interference
there is. I used the rounded end of a large ball pean hammer to create a minor
indentation in the passenger side of that pan to allow the motor to fit. About
3/8" deep and 2"x3" oval was enough.
There was alot more work here, and I don't know if it's just
because I have a Pinin but it is still worth it.