Night dimming relay.

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Dave B
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Night dimming relay.

#1 Post by Dave B » Mon May 25, 2015 9:45 pm

I think this may have been covered in the past, but is probably worth refreshing.
After rewiring the lighting system on a small trailer I bought last week, I plugged it in to my Mk2 2000 to test them and was disappointed to find they weren't working well at all. Back to the beginning, checked everything again and plugged back in, same result, no LH indicator with the sidelights on and RH indicator caused the rear lights to alternate dim and bright. Classic poor earth symptoms or so I thought! Out of desperation I plugged the trailer into the Vectra, lo & behold, everything working as it should.
Turning my attention to the Triumph, I soon discovered I had no rear LH indicator on the car either when the sidelights were on,(it doesn't go out in the dark!) and after a bit of faffing about with changing bulbs & adding temporary earths without any luck. Then I remembered the infamous 'night dimming relay' that hides behind the nearside boot trim panel on Mk2 saloons. I just pulled off the black earth wire on the unit to disable it & normal service was resumed, trailer et al.
So, if your rear lights start to play up, try the NDR first!
Last edited by Dave B on Mon May 25, 2015 10:04 pm, edited 1 time in total.
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Alan Chatterton
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Re: Night dimming relay.

#2 Post by Alan Chatterton » Mon May 25, 2015 9:58 pm

The night dimming relay was designed to dim down the brake and indicator lights when the side lights were on.

What an epically stupid idea. The rear lights are pretty dim at the best of times!!

Every car I have ever had with a NDR, I have disabled it straight away, by doing exactly what Dave suggested, pull the black earth wire off it.

Libby "had" one in the rear.............. it ain't there any more!!!!
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kevinw
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Re: Night dimming relay.

#3 Post by kevinw » Tue May 26, 2015 7:06 am

I think the idea at the time was a good one. In period, Triumphs had bright lights - much more so than the run of the mill cars on the roads in the 60s and early 70s and so slightly dimming the rear lights was a good idea to prevent dazzling following drivers. Now, two things have happened: first, with degrading wiring, poor earths and crazing of lenses, the light emitted will be less and second, there has been a huge escalation in light output of modern vehicles, so in comparison, the output of the rear lights of a Triumph looks feeble. Both our modern cars are terrible in this respect as they both have LED rear lights. The energy output of the rear sidelights is probably the equivalent of an early rear fog lamp.

It's another of those wonderful Triumph "this is a cracking good idea, chaps and we can be first to market" features along with petrol injection, 16 valve engines, single piece moulded plastic dashboards, printed wiring for the instruments. Everything that so nearly worked but needed more money thrown at it to finish the development.

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Alec
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Re: Night dimming relay.

#4 Post by Alec » Fri May 29, 2015 7:27 am

Hello Kevin,

I completely agree, sensibly, if the lights are bright enough for day light use (which they were) then it makes sense to reduce the output at night for the comfort of following drivers.
Modern cars are too bright coupled with high level brake lights and the widespread use of keeping a foot on the brake pedal when stopped.

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Mike Stevens
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Re: Night dimming relay.

#5 Post by Mike Stevens » Mon Jun 01, 2015 12:08 pm

A word of warning re the NDR. Just disconnecting the earth wire may not help. I had done that in the Stag and although all the lights worked before it's 1st post-restoration MoT, the brake lights didn't at the test itself! Checking through the wiring found that there was fault in the NDR.

It has now been removed with the relevant wires reconnected!

Cheers,
Mike.
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Dave B
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Re: Night dimming relay.

#6 Post by Dave B » Mon Jun 01, 2015 5:50 pm

Mike Stevens wrote:A word of warning re the NDR. Just disconnecting the earth wire may not help. I had done that in the Stag and although all the lights worked before it's 1st post-restoration MoT, the brake lights didn't at the test itself! Checking through the wiring found that there was fault in the NDR.
Thanks for the warning, Mike. Considering the MOT is due on the 2000 before the National, I've just been out to the garage to check, but all is fine at the moment, thankfully!
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Re: Night dimming relay.

#7 Post by Mike Stevens » Tue Jun 02, 2015 11:44 am

Hi Dave,

Good luck with the MoT!

Cheers,
Mike.
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1971 2.5PI Saloon Sapphire blue
1973 2.5PI Saloon rust some Honeysuckle
1973 Stag French blue
(1949 LandRover was blue should be light green!)

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