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Fog lamp wiring query


Gazzar

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My LWB has just failed the MoT on the fog lamp.  It goes off when the main beam comes on.

I thought that was correct.

Why would you have fog lamps on when the main beams are on?

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So, what do I do?

I think that the MoT guy is wrong, but he's only going by his reading of the guidance.

I think I'll phone the garage in the morning and have a chat.

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My 109 had a factory fitted rear fog light, and it only worked with dipped beam.  Likewise my wife’s Lightweight and my RRC.  The tester is misinterpreting his guidance.  Modern cars have different wiring, and their fog lights work with dipped and main beam, but not older models

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Didn't know about that recent reg. change , just about everything with a factory fit rear fog from introduction well into the 90's I think are dip only for rear fog , I'm pretty sure it was a regulation too .

Simplest  fix would be to power the rear fog from an ignition live , yours is an '81 so needs a rear fog I think?

thanks for pointing it out , something to look out for .

Steve  b

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So far, there seem to be no MOT testers involved in this discussion. Are there any on this Forum?

I ask because on the forum of the Series 2 Club there are a couple of MOT testers in active employment; they would probably have jumped in by now if this discussion was taking place on that forum.

Some research later I see the vehicle here is an S3. S2s and 2As are now covered by the rolling 40 year MOT exemption, which may be why the topic hasn't come up on that forum, for those who have retro-fitted rear fog lights.

Regards

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I have to say that the MoT guy had been very helpful and professional; he's bound by the rules, which is fair enough (I approve of tough MoTs, but I think this rule change is unfair and unnecessary).

 

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https://www.gov.uk/guidance/mot-inspection-manual-for-private-passenger-and-light-commercial-vehicles/4-lamps-reflectors-and-electrical-equipment#section-4-5-3

 

This states no other lamp must adversely affect the operation of the fog lamp.

What it is checking for here is bad earths/wiring faults, and not whether the operation of it is correct or not.

To pass with this tester, I don't think putting it to ignition live is the answer, if it ends up being long term. You should relay it from the sidelight wiring instead, that way you can't leave the fog light on by itself, without having the main lights on.

My old cavalier would extinguish the rear fog when on main beam - reason being if you are able to use main beam without blinding yourself there is no need for a rear fog.

 

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More links:

https://www.lrukforums.com/threads/rear-fog-lamp.233090/

 

https://www.honestjohn.co.uk/forum/post/index.htm?t=47711

 

Sorry, but your tester is minterpreting the rules. It is *designed* to work this way, and you shouldn't need to be modifying a vehicle design to get it to pass.

 

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I agree with your interpretation, but that's not the advice he was given. 

The side lights are a good idea, as is the relay, but I'll still pursue fixing the rules, via the DFT, as this is wrong.

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4 minutes ago, Bowie69 said:

More links:

https://www.lrukforums.com/threads/rear-fog-lamp.233090/

 

https://www.honestjohn.co.uk/forum/post/index.htm?t=47711

 

Sorry, but your tester is minterpreting the rules. It is *designed* to work this way, and you shouldn't need to be modifying a vehicle design to get it to pass.

 

The rules have changed, he's not wrong.  It's daft, and unfair, but he's following the rules.

Screenshot_2019-11-12-19-47-18-253_com.brave.browser.png

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I don't agree I'm afraid :)

Yes, the rules have changed, however this is not 'adversely affecting', if it is by design, adverse meaning:

'preventing success or development; harmful; unfavourable.'

it's none of those :)

You can appeal to further ups, the area manager for instance, you never know, they may make a clarification in the testing guidance.

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I'm with Bowie, that's a very poor interpretation... It annoys me giving into pedants, particularly when they're wrong, but it doesn't always make life easy. 

Swap out the supply into or bypass the inhibit relay should sort you out without much hassle. 

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