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MOT question - Stargazer {P}
Is there any requirement to test lights and indicator functionality using more than one function at a time during the MOT test?

The reason I question this is that I frequently see rear lights of cars that would pass the MOT test (all bulbs fitted and operational) if each function (rear lights, brake lights, fog lights, indicators, reversing) was tested independently..

BUT if the car is indicating for a turn and the driver applies the brakes then the indicator stops working, the brake light starts flashing or some other odd combination.

An electrical fault like this will not be picked up by the MOT test as I understand it is performed?

regards

Ian L.
MOT question - Cliff Pope
At my last MOT I watched, they turned all the lights on at the start and left them on for the duration of the test. I've no idea why.
MOT question - No Do$h
In the hope that a bulb would blow so they could try and charge you £30 for changing it?
MOT question - Stargazer {P}
but is this a requirement or just a convenience if performing a MOT test alone?

The last time I watched a test (very nervously after rebuilding my Mk1 Escort over a 2 year period) a trainee was dispatched to operate the various lights while the tester watched....each function separately.

I.
MOT question - Mapmaker
Sounds like a bad earth to me.
MOT question - Stargazer {P}
Mapmaker,

I agree, probably an easy fault to fix but would it show up or even fail an MOT test....not necessarily I believe.

I think the MOT test rules link posted somewhere here recently list what has to be tested but not exactly how they should be tested (ie test indicator and stop and tail lights simultaneously)

Ian L.
MOT question - henry k
Sounds like a bad earth to me.

>>
I agree. I fitted a supplementary earth on both rear light units to fix this common fault on Sierras.

If, in a traffic queue, you decide to act, how you can alert a fellow motorist to the problem with a clear description of the problem?

A circular movement of your hand at the window to indicate "please wind your window down I wish to converse with you?" followed by "your rear lights are all screwed up?" or "your rear lights work like a Christmas tree?"

The response could be variable!!!! Yeh I know mate!!
MOT question - No Do$h
This is often caused by people incorrectly fitting a dual-filament lamp with an offset-pin in to a normal lamp holder. This send a current to earth when a current is sent to the filament, causing everything else on that lightboard to flash like a mobile disco.
MOT question - Kuang
There's an interesting link here that has something to say on the matter - the extracts are from the official Vehicle Inspectorate manual.

www.ukmot.com/checklist/motcheck/motcheck_body.htm


Side lights and headlamps:
? Acceptable make/model.
? Dip and aim must be within specified perameters Stop lights, indicators and hazard lights*
? Acceptable make/model
? Lights,indicators and hazard lights must not interfere with each other whilst in operation.
? Indicators, stop lights and hazard warning lights function


Of course, that's not to say that all combinations *are* tested, but in theory they should be.
MOT question - Stargazer {P}
Thanks Kuang,

That is the sort answer that I was hoping for....these faults should be picked up but probably are not always.

Given the number of people who never seem to check their lights
and rely on the MOT test to pick this up. I try to get the message across to car drivers if they have a serious lighting problem but this is difficult if you are following the car.

regards

Ian L.
MOT question - Andrew-T
You have to check it yourself if you can't rely on the testers - for example with the car backed close to a wall.
MOT question - Dynamic Dave
for example with the car backed close to a wall.


I tend to use the reflection from a shop window, generally in the evening when their car park is all but empty.
MOT question - DeeJay
A good tester , carrying out the test as he has been trained to , would always find lighting faults such as these .The test routine is designed to cover "multiple" light defects .
MOT question - Tiffx19
As a tester I always fail cases like this,as in the testers manual,no lamps operation should affect anothers (i.e-a taillamp shuldn't dull down when an indicator flashes).Loads of older Fords fail on this because of bad multiplugs on the rear lamps, also Punto's and Peugeots are staring to show the same problems.
MOT question - IanT
Just want to support Tiffx's diagnosis.

My Peugeot 309 failed its MOT because both rear lights dimmed and brightened in tune with the indicators. The fault was a poor connection between the multiplug and the lamp unit on one side only. The poor connection was on the supply to the indicator - not the earth.

Fixed by squeezing the connector prongs in the multiplug to make a tighter fit.

Ian
MOT question - Stargazer {P}
Thanks for all the replies, especially those who actually do the tests....glad to hear that they should be picked up as a fail and not too difficult to fix.

I concur with the comments on Fords, Pugs and Citroens...I am seeing more and more of these cars with this type of failing on the road.

cheers

Ian L.
MOT question - Mapmaker
French electronics unreliable? Shurely shum mishtake. R21 I had went a bit loopy electrically near it's 15th birthday.