MOT Fail

[The Medway Handyman]

Took the handyvan (Renault Kangoo) in for an MOT Friday. Failed on a few minor points, one of which was "Nearside rear position lamp adversly affected by the operation of another lamp". Says the same for the nearside.

Took the clusters off today (the only simple thing to do on a Kangoo - bloody French)

No obvious fault, remade the earth connection to bare metal, WD40 liberally applied.

SWMBO returned from shopping so I got her to operate brake pedals, switches etc while I watched.

The van has the sort of rear lights where the side light just gets brighter when you push the brake pedel - e.g. it isn't a seperate brake light.

I can't see a thing wrong. Couldn't check beforehand tho cos I was alone.

I assume "Nearside rear position lamp" means 'sidelight' in plain English?

The sidelights work - so I can't imagine what they are on about? I though vehicle lights either worked or didn't?

Dave TMH

[John]

I think that what you are describing is a twin filament bulb. They have two contacts on the base and are usually (If I recall 5 and 21 watts) A bad earth can cause strange problems.

[Adrian]

The Medway Handyman gurgled happily, sounding much like they were saying:

Did you try the indicators & brakes at the same time, with and without the lights on?

Especially with dual-filament bulbs, a ropy earth can lead to all sorts of strangenesses if there's a dodgy earth - usually seen as Xmas Trees when coincidental paths to earth via other circuits start to run out.

[ARWadsworth]

Affected by the indicators by any chance?

BTW, just to rub it in, my van passed with just one advisory on Tuesday. The advisory was that there is rust on the rear of the exhaust pipe section. TBH I knew that last year and until it starts to blow there seems no reason to swap it.

[The Medway Handyman]

g

Yup

That could be it I guess. The earth connection was a terminal bolted to a welded on nut covered in paint. I took the paint off with a file. Now 100% certain thats OK.

Didn't have to chance to see what the fault might have been, was on my own.

Dave TMH

[Nick]

Dave, I think ' The van has the sort of rear lights where the side light just gets brighter when you push the brake pedel - e.g. it isn't a seperate brake light' refers to a double filament bulb. Check the bulbs, probably twin pole with offset retaining pins so that the bulb can only fit into the holder one way. The metal sheath of the bulb acts as earth. One filament for sidelight and the other for brake. If both filaments look good, clean the inner recess of the bulbholders and also the metal sheath of the bulbs. A little bit of emery tape wrapped round your finger works unless you have summat better. If that don't work, check all with a tester (but carefully) and preferably at the nearby multi-connnector. If these are good then test circuit between each pole and earth, but even more carefully. These days of electronics much damage can be done, it doesn't just blow a fuse any more :(( In short, check your bulbs, bulbholders and supplies to them.

Angle grinder not recommended, although..........

HTH Nick.

[Adrian]

The Medway Handyman gurgled happily, sounding much like they were saying:

Reflection in a window? Weight the brake pedal down with a toolbox or something?

[Roger Mills]

Indeed. It shouldn't be beyond the wit of yer average DIY-er to devise a way to hold the brake pedal down. I lean a heavy block of wood on mine.

[Roger Mills]

As others have said, it's pretty certainly an earthing fault. You need to make sure that:

1) the light cluster is properly earthed to the bodywork, and 2) the bulb bodies make proper contact with their metal holders

If the earths are not good, you get the sort of problem where a low powered light (5w sidelight) can be earthed via the filaments of a more powerful light(21w stop light or direction indicator) instead of directly, and can appear to be working ok until the brighter lamp is turned on - whereupon it promptly goes out. Seen it many times - particularly on trailers.

[Skipweasel]

Wife.

[Unbeliever]

Well it is The Meddling Half-wit posting - a simple solution to a simple problem that seems to be beyond him yet again.

[Andy Dingley]

You can diagnose rear light cluster earthing faults quite easily - look for a Ford or Renault badge. However they make them, they haven't got reliable earths to the rear clusters.

[Frank Erskine]

It would probably be much better to use a wire "earth" return, rather than rely on the chassis.

[John]

...or good earth contacts to the bulb caps.

[Andy Dingley]

A bulb with a failed cap contact just goes out.

A cluster with a failed earth to the cluster shows ghost ilumination through other bulbs (usually stop or fog, as they're the lowest impedance)

[Unbeliever]

No experience with the Kagoo but I presume that the rear light cluster has a 'buzz bar' type of common earth that could suffer from corrosion, there could be a problem with the wire connection to this, a problem where one filament on a twin filament bulb has failed (usually the lower wattage one) allowing a leakeage to earth across the indicator light etc, could be problem with loose bulb or even a poor connection to the live or earth bulb connections etc etc.

A *competent* DiYer usually finds the more persistent fault[s] by simply taking the cluster off and:

1 Check the incoming cables at the connector for power etc with a multimeter and clean off and remake the chassis earthpoint (with a French car, that could be halfway down the body of the car and in the most inaccessible of places [at least that was the situation on the wife's Citroen when the bloody headlight/side light cluster started playing up a few years ago]). 2 And if the above fails, take the rear cluster into a nice warm workshop, remove and check all the bulbs, then connect the cluster to a battery charger (or even a spare battery) and methodically work through every electrical trail using a multimeter or simply a good bulb with a couple of tails soldered onto it until the problem is found - usually around 15 minutes to check and resolve the problem.

[Frank Erskine]

Impedance? Are we talking AC car batteries here? ;-)))

[Tinkerer]

The commonest problem I have come across with dual filament bulbs is where one filament has broken and welded itself to the other. Thus when the brake pedal is pressed, current flows from the brake light circuit into the side light circuit. I have experienced this at least a dozen times over the years and it certainly fits the description of "Nearside rear position lamp adversly affected by the operation of another lamp".

[Dave Plowman (News)]

You've got a major problem if the 'chassis' doesn't provide a good ground. Since that's the way it's done on every vehicle made of steel. Only glass fibre ones need earth returns.

I dunno this vehicle, but the rear light ground may be clamped by a lamp unit fixing screw. Which is a stupid way to do it. But faster for initial assembly at the factory. Making a decent nut and bolt ground to a nearby convenient part of the body is the way to go.

[Dave Plowman (News)]

Are these twin filament ordinary bulbs - or LEDs? You can see the twin filaments by looking at the bulb. Usually have two contacts plus the cap which is the ground. Single filament usually just one contact plus cap.