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Technical Area for all the problems you have in the garage
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Roger King
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Re: Lucas L542 dual bulb conversion

Post by Roger King »

Did you try them first, Peter? My Mustang has LED tail lights, which I fitted using the old bimetallic flasher unit. They work fine with no problems.
Roger
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peterc
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Re: Lucas L542 dual bulb conversion

Post by peterc »

Roger
Quick answer is No I didn't check first.
Instructions were that the LED's would flash at incorrect speed so first job was to fit the new 3 pin flasher. It would be no problem to swap back to the two pin unit but that is the least of my problems at present.
I have been going round in circles today with an obscure problem in making the new lights work. Chris at Spiyda has been very helpful and he suggests that I have a brake light wiring issue.
Tomorrow I will investigate further but first impressions are that although I am fitting the OS first that the NS circuit might have a short. So maybe the wiring in the boot is the first place to investigate closely.
Perhaps my brake light pressure switch isn't broken after all?
Peter C
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peterc
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Re: Lucas L542 dual bulb conversion

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When dismantling the old L542 lamp assemblies to fit the new LED panel you do not have to cut through the entire back plate end to end as per the instructions. This is just as well as even with a multi tool plunge cutter it wouldn't be easy.
Merely cut through the short section from the bulb cutout area to the end with a junior hacksaw. Less likely to cause any injury to the hands than trying to hold the light steady whilst using the multitool cutter. Then careful manipulation with pliers you can pull / bend the smaller half clear of the small side tabs followed by the larger section.
Fitting the new LED panel does require the larger tabs to be bent well clear to ensure the LED's can clear the side of the unit when sliding it in.
Apart from the elongation of the holes in the body it was a fairly straight forward job.
The wiring is another matter and I will start another posting for some guidance please on my particular gremlins.
Peter C
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Paul Blore
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Re: Lucas L542 dual bulb conversion

Post by Paul Blore »

Hi Peter,

You only really need to bend one if the big tabs all the way up. You can tuck the new light board under the other one with it only partially bent up.
Have you run a new wire from your brake light switch to the new rear lights? You need to disconnect one of the wires from the switch (the one that doesn't have 12V on it) and then fit a new wire from that connection to both brake light connections (purple/green) on the new boards.

Paul
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clive
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Re: Lucas L542 dual bulb conversion

Post by clive »

Paul Blore wrote: Have you run a new wire from your brake light switch to the new rear lights? You need to disconnect one of the wires from the switch (the one that doesn't have 12V on it) and then fit a new wire from that connection to both brake light connections (purple/green) on the new boards.

Paul
Isn't that just replacing like for like? My wiring to the brake switch is green (+ feed) and green/purple to brake lights, so why replace it?
Cheers, Clive.

(If I'm not here I'm in my workshop or on the golf course!)
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Re: Lucas L542 dual bulb conversion

Post by Paul Blore »

It depends on whether you have two or three wires going to your rear lights. If you already have three with a separate wire for the indicators then you're correct and you don't need any additional wires. But if your car is wired as per original, with a flashing brake light for the indicators then you need an extra wire.

Paul
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Roger King
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Re: Lucas L542 dual bulb conversion

Post by Roger King »

You might want to edit that little lot for spellcheck, Paul... adding an extra Eire is a huge job, quite understand why Clive isn't keen to do it.
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peterc
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Re: Lucas L542 dual bulb conversion

Post by peterc »

During my testing I had been in contact with Chris at Spiyda to double check on the wiring as I don't have the DB10 relay and the instructions provided were only worded as to what to do with that set up.
Yes, Clive is correct that those of us ( probably most members) who do not have a flashing brake light relay already have the correct wiring between brake light switch and the rear of the car. So simply just connect the new plain green wire to our existing green purple on both sides.
Mine are all in and working but there is still a cross contamination between indicator and brake light detected by a slight pulsing of the brake light when both are working.
Separate posting added requesting for ideas of where to check for the problem.
Today's task is to recheck all the earth leads. Chris suggested I had perhaps pinched a wire and was earthing out a lead somewhere in the loom but checks with a meter showed no such shorting.
To be positive the new lights are very good and thanks again Paul for persevering with the design in liaison with Spiyda.
Peter C
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Re: Lucas L542 dual bulb conversion

Post by Paul Blore »

Hi Peter,
Are you sure that you haven't got the brake and indicators the wrong way round? From memory, the green/purple wire from the light units is the brake light, so that should probably connect to your existing green/purple wire.
Paul
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peterc
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Re: Lucas L542 dual bulb conversion

Post by peterc »

Paul.
You got onto the forum before I could correct myself.
Green and purple original to green and purple with the new lights.
The plain green goes to indicator of which the original is either green/white OS or green/ red NS.
So yes I have connected correctly.
Tried rigging up earthing direct to battery but didn't help NS
More testing needed.
Peter C
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