Rear lights being weird!

[mjstokes85]

Hi all, not been on here for ages so apologies if this is a know issue or something that is always posted about. My girlfriend has a Fabia Bohemia estate and currently has a brake light out. Upon investigating earlier I cannot for the life of me work out the way these rear lights work. According to what I’ve read online it should go: top light brake lights, then indicators, then reverse, then side/fog lights. However hers have never worked like that, and still don’t. The way hers work are: top lights: nothing! Indicators ( work fine) reverse (work fine) then brake and side light in one, and also fog, if you switch the fog on, the right brake light doesn’t work (basically the brake light becomes the fog light). I’ve tried everything, I can’t get the top lights to do anything, I can’t understand why the brakes are operating what are supposed to be fog lights whilst working as fog lights as well. I know this probably sounds confusing, that’s because it is! Fuses are fine, and brake switch must be fine as they work, just on the wrong bulb! Help!

[Breezy_Pete]

What year is this Fabia?

[mjstokes85]

56 plate.

[Breezy_Pete]

Any sign of wiring bodgery at the rear light cluster connectors?

[mjstokes85]

Not that I can tell, she’s had the car for about 6 years now, I just assumed they were all working fine, it’s never failed an MOT on them, but then after looking online I realised they don’t work how they should! First time a brake light has gone so first time I’ve had a look really.

[Breezy_Pete]

I'll try to think about this and get back to you tomorrow with wire colours and pin numbers as it should be.

[mjstokes85]

Just to let you know I have sorted it! I replaced the sidelight/fog light bulb and both brake light bulbs and now everything works as it should. The fog light/side light must somehow act as an emergency brake light when the brake lights don't work. Not sure why you have to put side light/fog light bulbs in both sides even though there's only 1 fog light?

[Breezy_Pete]

Glad you've fixed it but that is very strange.  There isn't usually even a wire going to the unused filament of the nearside twin filament bulb.  So how it could act as an emergency brake light bulb is beyond me.  Were they the correct bulb type fitted?

[mjstokes85]

It was also very odd with the side/light fog light, if I wiggled it about the brighter filament would come on as the sidelight and the less bright one would then operate as the brake light. Yeh they all looked to be the correct bulbs, the brake light bulbs I put in the other day for some reason didn't work (maybe just age as I've had them a while, but the filament looked fine), so the fresh ones today did the job. I made sure the side/fog was a P21/W4, NOT W5 like Halfords and most websites seem to think. Another odd thing was the third brake light in the spoiler came on as a sidelight as well for a bit. Me thinks something weird is going on with the wires somewhere, anyway, all working... for now.

[silver1011]

Was just going to ask, were you using P21/4W, a lot of people try to fit P21/5W and then get weird side effects...

 

[TMB]

1 hour ago, mjstokes85 said:

Not sure why you have to put side light/fog light bulbs in both sides even though there's only 1 fog light?

 

Because the bulb holders are the same on both sides.  They only provide a fog light on the driver's side so the 21 watt filament on the other side is redundant. It would be easy to run a wire across from the driver's side and then you'd have two fog lights. I guess they use the fog light on the redundant side for left-hand drive cars.

Edited 10 December, 2019 by TMB