Tail/stop light fault

[P-Co]

Specs:
BAY15D
P21/5W
Two parrellel legs with offset heights
Two bottom pos connections

So this isn't on the Clio but thought I would post anyway.

I have a rear light with this set up but the passenger one is constantly on as brake (21w) when side lights are on and doesn't change when pressing the brakes.

I have tested voltages and continuity, everything is ok, I have placed the bulb in the wrong way round (as can't lock it in) and it works corrently as expected.

Strange thing is that it is a waterproof BAY15D holder with rubber inserts around the cable, so I am wondering how or even why the pos connections have been swapped over or weather it was like this from factory, if so that is a poor check over, it is from 2004 though.

Just wondering if anyone has ever took the contacts out of one of these before as I haven't.

 

[White16valver]

I have tested voltages and continuity, everything is ok, I have placed the bulb in the wrong way round (as can't lock it in) and it works corrently as expected.

My apologies, this is not clear.

Are you saying the bulb works correctly if you turn it round the 'wrong' way?

If so, are the live/earth connections connected the wrong way round where it joins the rear lights' board / the rest of the loom?

 

[P-Co]

Ye, if I turn the bulb the wrong way it works, there is no board it is just the bulb holder pictured that twists into the rear light casing.

I have checked all electrical connections and the ground is correct (on the side of the holder) the two pos connections on the bottom seem to have been switched.

But now today it got interesting, the passenger one at fault now doesn't work as a brake light at all (probably blown again) but works as a side light now.

Also to make matters worse the drivers side has now done what the passenger was doing and now staying on as a brake light [emoji34].

So now the I have a really bright drivers side rear light and the only way to tell I am braking is the third brake light in the window.

I am wondering if maybe as the bulb twists in it slightly twists the lamp holders pins and they short across the bottom of the bulb intermittently causing it to light both elements together?

It's the only thing I can think of if all cables are ok.

 

[White16valver]

If the connections have been obviously switched round, you could swap them back?

Check your battery and all your earths before anything else - if they are not in the best condition, strange things can happen!

 

[P-Co]

I'm going to swap the pins on the passenger side as the readings showed they are the wrong way round.

The drivers side is fine though, earths on lights are fine and it is only the the brake/sidelight bulb that is having issues, no other elec faults which is why I am thinking that the pins are twisting when inserting the bulb and causing a short from sidelight pin to brake light pin.

Unless there is another unrelated earth causing havock somewhere as you say but will have to check them all out.

The missus has pinched the car to go to work today so going to have another look when she gets back.

 

[White16valver]

Hope you can get it sorted!