Wiring a Flick-Wipe
Switch
The following diagram is taken from an article on
the Lucas 2 Speed Wiper System at http://www.mgb-stuff.org.uk/wiper3.htm and adapted it to correspond exactly to the relevant wiring in
the Caterham installation,
so I've coloured the
wires appropriately and also added in the connectors provided to allow for the
installation of an intermittent wipe controller. These connectors also contain
one green/black wire for the windscreen washers so I've added it for
clarity even though it doesn't play any part in this. The diagram shows
the wiper switch in the "Off" position and the wipers parked:
Notice how the parking system works. When the
wiper switch is in the "Off" position, the orange/green wire is
connected by the wiper switch to the orange/blue wire into the motor which is
the low speed motor supply. When the wipers are in the parked position the
parking switch within the motor connects the orange/green wire to ground,
shorting out the motor via the wiper switch and stopping it dead. When the
wipers are away from the parked position the parking switch within the motor
connects the orange/green wire to the orange wire which is the fused power
supply. This powers the low speed supply to the motor to keep them moving until
they reach the parked position.
To wire in a flick-wipe switch, we need to be able
to convince the motor that it is no longer parked. We can't just power up the orange/blue
wire to drive the motor as that is shorted to ground via the wiper switch, the
orange/green wire and the parking switch, so trying to power it will just blow
a fuse. We need to wire in a changeover switch the overrides the parking
switch. One way of doing this is shown below:
Use a momentary switch with three terminals. It is important
that the switch is of the "break before make" variety, i.e. that as
the switch changes over the two outer terminals are not both connected at the
same time (in a "make before break" switch they will be and this will
also short the power supply and blow the fuse). I believe that the standard Caterham Flash
Switch should be suitable
(but I haven't test it) and this will match the design of the other switches in
the car.
To wire the flick-switch like this, cut the
orange/green wire and connect via the switch as shown, with the (usually
central) common terminal connected to the wiper switch side and the
normally closed terminal connected to the motor side. Then join another wire
onto the orange (fused supply) wire and take it to the normally closed terminal
of the switch.
When the flick-wipe switch is in its resting
position, the cut orange/green wire is reconnected and the circuit is exactly
as before. When the switch is operated, the motor is disconnected from the
short to earth through the park switch and temporarily powered from the orange
wire. Once the wipers start to move, the park switch changes over and the
flick-wipe switch can be released.
Wiring the flick-wipe switch above is convenient as
the various wires can connected close to the existing wiper switch, keeping the
wiring short and neat. However, some cars have an electronic intermittent wiper
controller box installed that activates intermittent wipe mode when the wiper
switch is briefly switched to slow speed and of again. Where installed, the
wiper controller is connected between the plug and socket shown in the
middle of the above diagram. The two connectors are unplugged from each other
and connected to the wiper controller. It detects the short pulse on the
orange/blue wire and will also therefore be triggered by the flick-wipe switch
if wired as show above. I think the solution to this where an intermittent
wiper controller is installed is to make exactly the same wiring changes, but
on the motor side of the controller connectors as shown below:
Note that I haven't actually tested the above, but the wiper
controller unit doesn't make a connection to the orange/green wire on the
switch side, instead controlling the orange/blue wire directly. There will
therefore be no pulse seen by the controller on the orange/blue wire when the
flick-wipe switch is operated and I don't believe it will therefore be
triggered into intermittent wipe mode. However, whether it responds as expected
to seeing the motor coming off park would need to be tested. I think it will
work OK. There are actually two different intermittent wiper control units, the
Lucas 6DA as used on the classic Mini and various Triumph cars and a Caterham/Technisol unit
which works in the basically same way, but may or may not respond in the same
way to the changed wiring above.
The other alternative, if the flick-wipe switch is
to replace the existing intermittent wipe function, is to remove the two
connectors from the intermittent wipe controller and plug them together, taking
it out of the circuit. The first proposed wiring diagram could then be used.
One other potential problem with this could be that
as the flick-wipe switch returns to its resting position, the wiper motor is
very briefly disconnected. Most switches snap from one position to the other
very quickly and this would not be noticeable. If using a vintage Lucas type
switch, sometimes they do not snap quickly from one position to the others and
the wipers may stutter slightly as the switch is released. If this is seen as a
problem, the flick-wipe changeover switch shown in either of the above diagrams
could be replaced with a simple momentary switch and a relay as shown below:
Replace this (Switch Only):
With this (Switch & Relay):
The contacts within the relay will always change
over very rapidly and any stuttering of the wiper motor as the flick-wipe
switch is released will be eliminated. This also has the added advantage
that a simple push button switch could be used, or a
two pin toggle switch as the switch itself does not need to provide changeover
functionality.
One final idea; there is a way of trying out any of
the above combinations without cutting any of the existing wiring. Holden
Classics sell complete sets of the 5-Way
Harness Connectors used for the
intermittent wiper controller. If you made up a small loom as shown below, you
could simply plug this in line between the existing connectors or on either
side of the intermittent wiper controller if installed and test before making
any permanent changes to the car. The orange wires could be neatly joined in
this case by crimping both wires into on terminal pin of one of the connectors.
The connector shown with solid terminals is the connector with solid male pins, the connector shown with hollow terminals is the
connector with hollow female sockets. The position of each wire in the
connector may be copied from the existing connectors:
A similar loom could be made using the relay if
required.
The loom shown below may be used to combine the
ideas above to make a plug in loom using a relay which allows the existing main
beam flash switch to perform a dual function; down to flash main beam, up to
flick the wipers. The existing flasher switch should be replaced with APEM
637H/2+U282 which has a
MOM-OFF-MOM action. The existing brown/blue wire should be connected to the
central terminal, the existing blue/white to the end terminal corresponding to
the switch being pressed downwards and the new orange/purple wire should be
connected to the end terminal corresponding to the switch being pressed
upwards.