Electric Windshield Washer for Beetles

Tiring of the spare tire running flat, many owners have opted to install an aftermarket electric pump for the washer. That's the easy part. In this case, I mounted the pump to the brake reservoir with a couple of self-tappers.  The relay (gotta have a relay!) controls the pump motor.

But where does one mount a pushbutton on the dash to operate the pump? Especially if the car has some value as a show car, who wants to gouge the dash with another hole?

Later cars ('72 up) with the wiper control on the column stalk are relatively easy to modify without adding another button. This is what the wiper/washer section of the stalk switches looks like:

Remove the 2 screws holding the black plastic valve and conjure up a bracket to mount a tiny Microswitch. Late wiper switches had provision for additional wires in the plug (only one more is needed), so that part is fairly neat too.
(I haven't worked on that project yet, so I don't have any photos, but others have done it.)

Earlier cars with the dash-mounted switch pose some additional hurdles though.

Remove the plastic valve section by drilling the rivets out. Takes some patience as they will probably spin.

A couple of 4-40 screws will hold the assembly together.  Try not to let the switch come apart as the detent ball inside will get lost.

My first choice was a Microswitch like this one.  The model V-3 is common and easily found:

I made a crude bracket out of thin aluminum to mount the switch, using the 4-40 screws:

I drilled a small recess in the switch operator to accept the plunger rod:

The top view looks like this:

Now for the hard part.

All that keeps the button from falling out of the wiper switch is the way the button stem is pressed into the rubber valve diaphragm.  With the valve discarded, there is nothing to retain the button.

Additionally, I wanted some more spring force than the rubber diaphragm provides in returning the switch to the off position.  I came up with a coil spring attached like this:

The end of the spring passes thru a tiny hole drilled in the bottom of the wiper knob:

Once the button has been pushed into the knob, the end of the spring gets cut off and bent over to keep it captive.

This scheme did work, but I wasn't entirely happy with the reliability aspect.

PLAN "B"

Next, I considered retaining the rubber diaphragm in conjunction with a much smaller (and more sensitive) Microswitch. The first step was to cut the valve body as shown here:

The parts then look like:

A small bracket would be made to attach the Microswitch to the end of the valve body with the 4-40 screws.

I didn't pursue this scheme any further because I wasn't satisfied with the switch operation.

PLAN "C"

I was looking for a switch that could be actuated directly from the rubber diaphragm when I remembered having some tiny pushbutton switches often used on printed circuit boards.

I came up with this arrangement.  The switch plunger actually enters the hole in the valve body and the rubber diaphragm directly pushes on it.

More views of the assembly:

And, finally, the wiring:

The tiny switch can't carry the current required by the pump relay, so I added a transistor (black square) to interface between the switch and relay.

The circuit is shown here:

Well, there you have it.  Probably "over-engineered".

Lots of ways to skin the cat, as they say.  See what you can come up with...