master 2004 rear lights issue

[FiremanT]

My van is overdue the MOT. I was intending to take it on tomorrow, so did the basic checks.
On the rear light cluster arranged vertically, reading down there is a red,2 x white and then a red lamp. I have never really observed the lights before. When the driving lights are selected, the TOP lamp comes on. With the driving light OFF, the brake lamp is also top. With the driving lights ON, applying the brake causes the same top light to illuminate brighter (than driving light).
The bottom light does not come on at all.

Does anyone have any ideas as to the likely cause of the problem? I assume driving light and brake light is separate top and bottom lights, but I don't know the correct order.

Sorry of this sounds stupid, and thanks in advance

 

[Burnerman]

Crazy things happen when the earth to the lamp cluster isn't as it should be.......try running a separate wire to the bodywork from the cluster if you can.
Another weird one happens when a single filament bulb is mistakenly inserted to a twin filament bulb holder!
John

 

[FiremanT]

Thanks BM, I will try that tomorrow.
I've been thinking about the bulb getting brighter when the brake lamp is on. Will this be because it is a dual filament bulb, or because there is more voltage (Although I dont see how we would get more or less than 12V).

I assume I should expect single filaments? I don't suppose you know whether the brake should be top or bottom?
Thanks again

 

[Burnerman]

Sorry I can't help with which lamp is which, but if you haven't replaced any bulbs recently then all should be well there.......to check, pop each bulb out in turn, and if there is only one centre connection within the bulb holder then a single filament bulb is the type you need.
I believe the earth wire is black on these, and that connects the outside of each bulb holder to the vehicle body......that's the likely culprit!
Be lucky with it - they can be a right PITA at times!
John

 

[Mursal]

Bottom red might be rear fog?
To Test:
Dipped main beam, ignition on, and the rear fog switch turned ON, outside one (offside, behind the driver) should light? The inside one (nearside, behind passenger) might not have anything inside, depends.

Top red seems to be working OK, no?

Good luck ............
Have it nice and clean underneath, keep them sweet .........

 

[FiremanT]

Bottom red might be rear fog?

Top red seems to be working OK, no?

QUOTE]

DAMN.... Totally forgot about Fog Lamp!!

Thanks. Will check.

 

[FiremanT]

Crazy things happen when the earth to the lamp cluster isn't as it should be.......try running a separate wire to the bodywork from the cluster if you can.
Another weird one happens when a single filament bulb is mistakenly inserted to a twin filament bulb holder!
John

BM, the problem, if there is one, is on BOTH clusters Presumably , a poor earth on a cluster would only affect that cluster, or is there a common earth?

 

[Burnerman]

Quite often the earth is common, unfortunately but it does no harm to re - earth both clusters.
Towbar wiring can also play havoc with lighting!
John

 

[FiremanT]

Right, I am so embarrassed! I only thought I had a problem 'cos there was a pair of reds not lighting. These are, in fact, fog lamps, which I had totally forgotten about.

So the top reds are obviously, now, dual filament bulbs for driving/brakes, so are okay.

Thanks for your help and replies - and I now know, for the future, to check earths carefully, as well as remembering basic functions.

Van now booked for tomorrow, so hopefully will fly through

 

[FiremanT]

Turns out the lights were the least of my worries. Failed. Miserably. Grrrrrrrrrrr

 

[Burnerman]

Sorry to hear that!
Do tell?
John

 

[Mursal]

That's a pity, but they seldom pass the first time over here.
Bit of a revenue stream for them, so don't stress to much ...........
How bad is it?