Rear Break Lights not working

[paulod]

Hi all,

I know there were similar posts about this but I have a couple of questions. Both my rear break lights have stopped working. However the top light above the door does work. Are they all controlled by the same break light switch? If so this would mean the switch is good. I have ckecked all the fuses and bulbs and they are all good. Where exactly is the break light switch on my model. Is it near the foot pedal? The year is 2014 and VIN is VF77B9HNODJ880534.

Thanks for all the help.

[LukeC]

I think that the switch is the same for all 3 lights, my suggestions have already been ruled out by yourself. I can't think that wires would have broken on 2 bulbs simultaneously, nor would it be likely on the sides, it's more likely on the high level where it moves.

It's not something else simple like corrosion on the contacts is it?

Sorry that I'm not much help.

[paulod]

Thanks Luke. If there was a break in the connection on the offside would this affect the nearside as well. i.e is the circuit in series?

[LukeC]

I'm not sure, mechanics and electrics aren't really my field of expertise. In my mind I was just thinking worse near the bulbs, but I'd forgotten all of them going back to the fuse boards. That question would have to be answered by one of the more knowledgeable members.

[Multispacer]

Do all the other lamps work on the rear clusters? [ie the indicators, reversing lamps, fog lamps]

[paulod]

Do all the other lamps work on the rear clusters? [ie the indicators, reversing lamps, fog lamps]

Yes they are all good.

[Multispacer]

Do all the other lamps work on the rear clusters? [ie the indicators, reversing lamps, fog lamps]

Yes they are all good.

Okay, I'm thinking along the lines that this must be something upstream of the light units, as you've checked all the obvious items lamps/fuses and if it were something like a poor earth, none of the other lights in the clusters would work, as they use a common earth [when the brake light failed on my Berlingo, I also lost the rear fog etc and that was a broken earth wire]

Have you tried the old favourite with weird electrical problems on the Berlingo, a BSI reset?

BTW what was the fuse number that you replaced?

[shtu]

is the circuit in series?

Brake lights aren't wired in series - a single bulb failure would result in all other bulbs failing to light.

Is there a towbar fitted? (in particular, an aftermarket one?)

This unfortunately is back to basics of checking for voltages\earths at the various points. This thread on FCF seems to have a suitable wiring diagram but I can't guarantee it - https://frenchcarforum.co.uk/forum/viewt...hp?t=59929

The fact that SOME brake lights work would suggest to me that the switch and BSI are probably fine. I'd be looking to see if the tail lights are fused seperately from the high level, where the output leaves the BSI, etc.

Note that the FCF thread immediately mentions towbars too.

[paulod]

There is no tobar fitted.
I took off both housings to check the bulbs and connectors again.
This time the bulb on the offside came on. I have checked and rechecked for loose connections etc but can find nothing.
The nearside then came on a few mins after so really strange.
I have no trust now in case they both fail again and I will not know.
If the pedal switch was dodgy surely none of the lamps would come on.
I will keep a good eye on them again and see if I can get some consistancy in them failing again.

Very strange.

[Multispacer]

There is no tow-bar fitted.
I took off both housings to check the bulbs and connectors again.
This time the bulb on the offside came on. I have checked and rechecked for loose connections etc but can find nothing.
The nearside then came on a few mins after so really strange.
I have no trust now in case they both fail again and I will not know.
If the pedal switch was dodgy surely none of the lamps would come on.
I will keep a good eye on them again and see if I can get some consistency in them failing again.

Very strange.

Okay the fact they've started working again after disconnection/reconnection, I'll suggest [and I know this is a bit of a pain] remove both lamp units again disconnect and give both connector plugs a good spray with either electrical contact cleaner or IPA.  [Note only use proper electrical contact cleaner or IPA as it's not that expensive and using either WD40 or other types of solvent on electrical connectors can cause other problems as they leave a residue]

You could also separate the circuit board from the lamp unit and give the other side of the circuit board a good spray with electrical contact cleaner. 

Oxides can build up on electrical connections especially relatively low voltage/current connections and provide enough of a resistance that you get failures. Electronics in general don't like being exposed to weather extremes and the rear lamp clusters are prime examples of that.

Finally if you park up on a driveway normally at home try rigging up some sort of mirrors behind where you normally park at an angle that you can check your rear lamps every morning before setting off on a journey.