Brake/tail light bulb works, but not when braking

[ScarySquirrel]

Hello,

I understand that the P21/5W (380) bulb on a Mk2 Ph2 Clio is a single bulb which acts as the tail light, and gets brighter when you brake.

Mine works fine as a tail light, but when I brake it doesn't get brighter to indicate braking. This is on the driver side. The passenger side and spoiler brake light are working as normal.

Any ideas what could be wrong?

Thanks

 

[SC03OTT]

Is there not two filaments in the bulb? I have a sneaky feeling there is.

Like so:

The braking part will have blown.

 

[ScarySquirrel]

Oohhhh, that makes sense.

I'll just get a new bulb then, yay