Mod Description

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

Mod Details

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Smart, didn’t make it easy to change the heater switch. Designers rarely consider things like that. However, despite being hidden by the dashboard, actually removing the switch isn’t that hard.

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 3 problems, either a wire or connector over heats (covered later), the switch contacts burn or (and is much less likely) the fan connector to SAM N11-1 pin 2 over heats (thanks to Adrian P for that).

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. Right Hand Drive

Lower Removal Method

Remove the speedo.

Detatch and swing down the flap under the steering wheel.

Remove the lower steering column surround.

Underneath you should find a polystyrene block. Slide it out.

Look into the hole towards the centre and you’ll see the switch with its single Torx screw. Pay attention to the white power connection at the back of it, does it look burnt?