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Electrical guides and mods

Extra Window Switch

Yes, the smart is narrow but the lack of passenger window control on the driver's side is unforgivable. This is double trouble if you own a

Modification Details

Buy Or Make?

The 1st kit, I bought. If you want to buy one, look here.
Click here or scroll right down near the bottom of this page to see the fitting guide.

The 2nd kit, I made. I had the wire and crimp terminals so all I needed was relays and the switch.

Making your own is very satisfying, not as hard as it might seem and will cost you less than £10.

Making Fitting The Home-Made Kit

You'll need the following:
Spade connectors (red and blue),
Straight through butt connectors,
2x 5 terminal automotive relays,
A centre bias (on)-off-(on) switch,
Thick and thin wire,
Soldering iron & solder or those terrible quick connectors.

Remove the Torx25 screws from the handle and the Torx20 screws from the door pocket.

Grab the bottom of the door card and pull it to disengage the clips.

Pull the door card towards the font of the car to release. Repeat on the other side.

You now have access.

Reach behind the switch on the passenger's side and push it out from the back.

Then disconnect the switch by pulling the unit from the connector.

The connector has 4 wires. We will be using some of these later.

Now you need to create the wires. Take a wire approximately the same size as the wires to the standard window switch.
Crimp a red spade terminal on the end. Measure back about 5cm and cut away the sheath.
Bend the exposed wire and then crimp a blue spade connector to it.

Like this...

Keep doing that until you have 4 spade connectors (1 red and 4 blue) on the same wire.
Make the final length of wire about 1 meter long. You only need to make 1 of these.

You'll also need to make 4x 30cm wires with a red spade connector on 1 end and a butt connector on the other.

Take your centre bias switch and connect 4 meters of cable to each of the outside terminals.
Use a 15cm piece of cable for the centre terminal.

A centre bias switch is like the existing window switch. Returns to the centre after being pushed up or down.

Use heatshrink or electrical tape to protect the connections.

Now you drill a suitable sized hole in the driver's side door. Check the specs of the switch you bought.
Either drill a pilot hole and then a full sized hole, drill immediately with the full sized drill bit or...

Drill a pilot hole and then use a tapered reamer to adjust the hole to suit the switch.

A correct sized hole.

Push the 3 wires that are attached to the switch, through the hole and push the switch in place.

On the driver's side, look at the wiring connector for the original window switch.

Cut back the sheathing to the brown wire (earth)...

...and wrap the wire that comes from the middle terminal of the new switch.

Solder the wire to make it secure and then wrap it up with electrical tape or fabric loom tape.

The final 2 wires from the new switch will need to be run out of the door, across the front of the car and into the other door.

Look at the front of the door, you'll see a channel that carries cables out of the door.

Pull it out of the door...

...and open it up.

Run your 2 cables through the channel and refit it to the door by pushing it into position.

Remove the front panels...

...and the route the cables safely with the existing cables so they don't rub.

Dress the wires across the front of the car and into the passenger door using
the same method as before regarding the removal of the cable channel.

Now these 2 wires are in the passenger door, strip the ends and crimp a red spade connector to each one.

On the passenger door, pull back the plastic and look down into the door.
You'll see 2 wires going into a hole in the weathershield.

Reach in and disconnect it. This is the window motor connector.

Take your 2x 5 terminal automotive relays. These can take 12 volts and 20+ amps.
I taped mine together to make it easier and more neat.

All relays have numbers for the terminals. 30, 85, 86, 87, 87a.

Take your existing cable that used to control the window motor...

...and cut it about 8cm back from the connector. Crimp a 30cm wire (that you made earlier) to each one.
So you'll have the window motor connection, 2 straight butt connectors, 2 extension wires with red spade terminals.

Crimp the other 2x 30cm wires (that you made earlier) to the back and green cables coming from the door.

Here are the notes I jotted down on the back of a jiffy bag.

Take the 2 wires that ran from the driver's side to the passenger side door and plug them in a terminal 86 each.
The motor connector that you have loose, plug each spade connector into an 87A terminal.
The green and black cables coming from the door, plug each spade connector into a terminal 30.

The final 4 terminals on the relay (both 87 and 85) are for the remaining power cable that you created.

So, the cables (green and black) from the window motor connector 87A on each relay.
The 2 cables (green and black) coming from the door, connect to 30 on each relay.

The cables that came from the driver's side door, connect to 86 on each relay.

Look at the existing window switch wiring. Find the black/yellow wire...

Remove a section of the sheath...

Take your multi-ended cable that you made...

...wrap the end of the long cable around the exposed wire...

...solder the wires for a good connection...

...and then protect it with electrical tape or fabric loom tape.

On the end of this final cable are 4 spade terminals. Connect them to the remaining terminals on the relays.

Plug the window motor back in. The relays and wires can now be tucked into the door...

...and the long cable dressed neatly out of the way.

There, you can't even see it all.

Turn the ignition to position 1 and try both switches for the passenger door. If the new switch on the driver's
door operates the window in the wrong direction (pushing the switch up makes the window go down)...

Disconnect both connectors on relay terminal 86 and swap them around. The switch will work properly now.

Refit the door card, the interior door pull and the door net.

Fitting The 
Bought Window Kit

Remove the door handles with a Torx 25 and the four pocket screws with a Torx 20.
Pull the door cards off carefully and look directly down where the arrow
shows on the passenger side.

You will see a black connector that goes to the window motor; unplug the connector.

Pull the connector away from the door and cut the wire about 5cm away from the plug.

Join the green wire of the connector to the green wire with
the crimp connector with 'motor' on it.
Join the black wire of the connector to the black wire with
the crimp connector with 'motor' on it.
Crimp the connections, I used a pair of mole grips as I didn't have a crimping tool.

Join the remaining green wire to the green wire with the
crimp connector with 'schalter' on it.
Join the remaining black wire to the black wire with the
crimp connector with 'schalter' on it.
Schalter means 'switch' in German. Again, crimp the connections as above.

Tape all the wires together and reconnect the plug into the window motor.

Pull the connection off the back of the existing switch and find the Black/Yellow wire.

Locate the Blue/Red wire from the kit.

Using the red snap fit connector, join the Blue/Red and the Black/Yellow wires together.

Remove the guide from the front edge of the door by inserting a screwdriver into the top.
Unclip the 2 clips on the guide and fold it open.
The kit should have 2 remaining thin brown wires,
push them out of the hole and clip them into the retainer.
Clip the retainer back onto the door.

You can route the wires around the front panel with it still on but it is a lot more
precise if you take the front panel off, that way you can trace the original wiring.
Zip tie the wires to whatever you can and route it to the other door.

As before, remove the guide, thread the wires in and replace the guide.

Pull the brown wires into the door and get your drill ready.

Drill a small pilot hole below the driver's side original window switch.
It's a good idea to disconnect the wiring so you don't drill through it.

Using a 19mm or 3/4 inch spade bit or hole boring bit,
drill a nice clean hole, tidy the edges up.

Take the switch found in the kit and using a snap fit connector connect the short brown wire from the centre
of the switch to the brown wire on the connector you just pulled from the back of the existing switch.

Take the 2 crimp terminals from the kit and attach one each to the brown wires
you previously routed around the front of the car. (I soldered my connections).

Thread the 3 brown wires through the new 19mm hole and attach to the new switch.
Test which is up and push the switch into the hole the right way up.

Replace the front of your car and the door cards. Job done.

How Does The Kit Work?

It's a very simple design based on the car's original wiring;
it uses two relays, one for up, one for down.
The Blue/Red wire in the kit connects to the 12 volt wire - when the small switch
is activated it sends a current through the coil which switches the relay.

As the relay switches it sends a voltage to the motor on one relay
(depending on the direction of window travel), The voltage goes
through the motor and back down the original wiring.
At rest, the original switch is earthed on both sides so therefore completes the circuit.

Adapting The Kit

Previously I had thought it would have been good to have the window switches situated either
side of the gear change housing. The idea was to use a pair of cabrio roof buttons and housings
that clip onto either side. Hopefully I will be able to add this later on.

In the mean time, feel free to do it yourself. Here is the underside of the cabrio switch.

Pin 1 is not used,
Pin 2 is not present,
Pin 3 is a power output (up),
Pin 4 is a power output (down),
Pin 5 is the power input.

The voltage goes in through pin 5 and depending on which end of the switch is pressed,
it will output the power to either pin 3 or 4.

In the kit shown above, the 2 brown wires that usually go across the front of the car should
be attached to either pin 3 or 4. The power can be taken from anywhere to pin 5.

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