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Electrical guides and mods

Roadster Heater Switch

The Roadster heater switch is a weak point in the system and can fail, here is how to fix and prevent it happening

Modification Details




 Smart, in their infinite wisdom decided that to change the Roadster heater switch, the dashboard
had to be removed. This was several hours of labour for no reason. Mad dan from TR.n
 noticed
that the single fixing for the switch was accessible without the dash being removed.

Here is my interpretation of it plus an interesting addition.

Symptoms

Unlike the fortwo 450 heater blower failure, the Roadster heater can fail in any way.
The most common failure is that nothing works at all but any of the speeds can stop working individually.

What Goes Wrong?

There are 2 problems, either a wire or connector over heats (covered later) or the switch contacts burn.

Even though the contact pad on the switch is designed to reduce the possibility of arcing, the gradual step up in power over the contacts can cause a spark. Every time you get a spark you get a small build up of copper oxide that has a higher resistance than the rest of the copper. Over time, the copper oxide builds up so much that the resistance of the switch increases. More power is used to create the connection which, coupled with the higher resistance, causes a lot of heat which damages the tracks, surrounding plastic, wiring and sheathing.

This is usually evident by the build up of a black/brown layer on the
contacts and possibly a burnt connection and/or brown (earth) cable.

Replacing The Switch

Remove the speedo and the stalks.
Look in the direction of the arrow to view the switch.

Image

You can see the switch unit and the Torx screw that holds it in place. Whilst you are looking at
the switch, pay attention to the white power connection at the back of it, does it look burnt?

If it does then click here.

Image

You can remove the flap under the steering wheel and remove the polystyrene block...

Image

...to see the switch from underneath.

Image

Removal of the screw can be done with a standard Torx screwdriver then the switch can
be pulled far enough towards the footwell to disconnect it if you need to. Replacing is awkward
but you can get your hand up behind the dash to hold it in place while you replace the screw.
A Torx screwdriver with a magnetic head will make this a lot easier.

Burnt Connections

If, during the inspection of the switch, you see burning around the white power
connection, it will need replacing. Go to smart and buy a loom repair kit for the heater
switch. This will consist of a new connector and short lengths of cable protruding from it.

Smart part number Q 0015415V001000000 (Blower switch repair kit).

Remove the switch as mentioned in the previous step, disconnect it, check it for faults
and clean it. Cut the old burnt wiring connector off and use crimp connections to join
the new connector to the existing wiring loom.

Refit the switch as before and test.

Cleaning The Switch

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