Select cars to narrow search
dont search for 599cc fortwo modsdont search for 698cc fortwo modsdont search for 999cc fortwo modsdont search for roadster modsdont search for 453 smart modsdont search for forfour mods

Electrical guides and mods

Roadster Cabin Fan Fault

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
that the single fixing for the switch was accessible without the dash being removed.

Here is my interpretation of it plus an interesting addition.


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.


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.


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

Image see the switch from underneath.


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


The rest of the information held in this guide is locked to members of Evilution only, you can login below or click this link to find out more.

Enter your login credentials here


Click if Info Helpful

Contact us about mod
Terms and Conditions
Site Disclaimer

© Copyright 2013, all rights reserved.