A bit random this, but I wonder if any XJS owners have some experience of successfully fitting LED bulbs to the rear Stop / Tail lights?

I've been working on the problem with Gil Keane from www.bettercarlighting.co.uk Gil is great, hugely enthusiastic and professional in his desire to get better quality lighting available for our classic cars.

I have tried some of his new Canbus-compliant bulbs, but I've still got a problem of how to persuade the bulb failure system to recognise the lower current draw of these LED bulbs. And I don't want to rip the system out or remove the warning bulb. I would just like it to operate correctly with LED Stop / Tail and Front sidelight bulbs.

So, I just wondered if anyone if anyone had ever examined or taken apart one of the bulb failure sensors, shown in the second pic, to understand how they operate, if they deteriorate etc. If I even just wiggle the terminals slightly on that module whilst the lights are on, it seems to slightly affect the voltage readings on the module terminal and also the frequency of the bulb failure warning light pulsing. Clearly, these modules are quite sensitive. So I wonder if I can do anything to them, or if fitting new ones might make a difference. I'm guessing they just work by expecting a certain current draw and sending a signal to the failure system if the current draw is less than expected? Or does it compare the current draw between the left and right modules and flag up if it seems a difference? If the latter, then LED bulbs should be fine if fitted to both sides, shouldn't they?

Any thoughts gratefully appreciated.

Paul

 

https://www.classiccarleds.co.uk/pro...sh-turn-signal

 

Right.

They're just a heat sensitive bi-metal switch. The heat comes from xxx-current draw. Less draw = less heat = they don't work.

No, they're not that smart. All they recognize is heat. They have no idea if the heat is coming from one bulb or twenty bulbs. If there's enough heat the bi-metal switch will work. If not, it won't.

Cheers
DD

 

Tks Doug,

That would imply that they work really quickly if a single press of the brake lights can recognise a bulb being out?

It seems that I might either need some cleverer Canbus bulbs that can emulate higher current draw, or else a ballast resistor as per Pete's suggestion in earlier post?

Paul

 

The brake lights have a unique failure detecting module. Remembering how it works is taxing my brain a bit at the moment

I'll do some mulling

Cheers
DD

 

Ah Doug,

You're right, I've found a separate Stop Lamp failure switch in the wiring diagram.

I guess if I had to fit ballast resistors, that means I'd have to fit separate ones on the two circuits on those twin filament Stop / Tail bulbs?

Paul

 

Correct.
The problem with fitting resistors (I think) is that you then do not have the benefit of reduced current draw.

But, Paul, do you have the BCL headlight bulbs, and what is your opinion of them? I am tempted, once I have saved up. I have the top notch super Osram normal bulbs (in the twin headlight setup) and they are great; but I am interested in reducing the current draw.

 

Greg,

As you may know, in the UK, we've had this weird legislative debate been going on as regards the fitment of any non-Type Approved Bulbs. The current position we've arrived at is that LED upgrade bulbs can't be classed as road legal because they cannot be E marked or have the British Standard mark. The reason that LED upgrade bulbs can't be E marked is simply because no legislation exists for the use of LED technology in a headlight unit built for halogens.

Therefore, we had cars getting their MoT inspection failed if LED bulbs were fitted. Witha lot of pressure from people like Gil Keane, they've now changed the rules so that any car registered after 1st April 1986 will be failed if the tester sees a non-halogen bulb fitted. But cars registered before 1st April 1986 WON'T be failed for having non-halogen bulbs. The logic? I don't know! It mist be something to do with thinking that cars older than 35 years can benefit from light upgrades, yet vehicles newer than that should stick to their original headlights! Madness!

So, legally I can upgrade my 79 pre-HE if I want, but I can't upgrade my 94 AJ16 XJS!

So legally, I can't actually improve the safety by fitting the rear LED bulbs either. But no MoT tester is going to try and take my lights apart to check what bulbs are fitted in there!

So, as regards headlight bulbs, I'm just running Philips Xtreme Vison +130% halogen upgrades (which have now been superseded by their Pro 150 bulb). I really like the Philips bulbs which I have in my everyday car as well. I've heard similar good feedback on those running the Osram Nightbreakers.

Eventually, the legislators will realise the stupidity and just change the rules to recognise beam pattern and height only, and then we can all do the right thing to be safe and be seen.

Paul

 

Man that is stupid. Most of issues come from are not the led themselves but the type of beam they put out. Because old style housings they weren't designed for led lighting so when you put in a led bulb in an old housing it scatters the beam everywhere. And then it's also not aimed correctly so it blinds other drivers. Hence why factory led lights you can see the beam basically stop at a certain heigh because the housing is designed to cut off the beam as to not blind oncoming drivers.

When converting to led new housings are actually better to aquire. That's why I will eventually try and get the quad light housing and put in a complete led housing (5 3/4 inch) round. Worse case I gut the original housing amd fit one in there or fab up a housing from scratch.

There are a few company's out there that you can send your factory housings amd they will convert it but it's big money.

 

If you need to add resistors to maintain load, other than the maintenance 'stuff' LED's are of no value since you're burning the same energy anyhow - but then if you fit LED's get rid of the bulb warning - it becomes mostly irrelevant if you get quality reliable LED's.

Beware however the LED colour as they may not provide what you expect intensity wise - or final colour - many of the older plastics work well with the tungsten spectrum but not necessarily that of an LED and red doesn't look red any more - same issue if you replace the dash bulbs with LED's.

If you get the colour and brightness right the MOT tester won't give a rodents rectum - but - there's always one - beware of insurers - if you're in an accident and they can use the 'non legal' light emitters as a get out of jail card they will. In the UK it isn't worth the risk to use non 'e' marked and road legal items but a lot do.

I use Osram nightbreakers in all our non HID cars, I buy the appropriate bulbs in bulk and keep spares in the cars, for me LED isn't worth the hassle.

Legislators in the UK adopt common sense - not in my lifetime - its a bit like them actually getting a road user to design a road instead of a pedestrian - or accepting that walking in the road should be the walkers liability not the drivers - soap box at the ready.

 

Het guys.
Does the XJS system only activate the bulb failure bulb for the rear brakes as I have read in my service manual. But I have put LED's in front park lamps, front indicators and optic fibre and it is still on with the ignition in position 2 with lights on.

 

Both the stop lamps and marker lamps have the system, there is a separate module for the stop lamps system, and for the markers separate modules for each actual bulb at the rear, and one module for both markers at the front.

 

I'll have a slight update on this at the weekend. I've been trying out some things with partial success. I'm getting close to a series of options / recommendations as to the best way to go on led stop / tail bulbs on my facelift model.

Paul

 

I have the LED H4 and H1 from BCL fitted to my quad headlight setup on my '92 MY, and have the DLR high intensity park/sideligh/pilot fitted and use as a DLR light.
bettercarlighting.com

 

So, after 3 months, I'm still gradually trying to work through this. I THINK I've now discovered an answer to the tail light bulb failure illumination problem without having to bypass the modules, OR without having to install resistors (which I didn't want to do as it loses the benefit of reduced current draw and also means you might have a dangerous problem if someone then changed the LED bulbs back to filament bulbs).

Therefore, my next challenge is the brake light failure module. On later facelift cars it was moved from under the centre console to the inner left-hand wing. Unfortunately I suspect the cheapest and easiest option is to bypass that module So, before I start pulling apart the boot strut mounting and reinforcement plate, does anyone have a clear photo of where exactly it is mounted behind the plate, so I can work out if it's possible to sort it in situ?

Tks

Paul

 

I'll court controversy and go with the bypass the things and remove the indication from the dash - don't think it is an MOT thing and if it is it shouldn't be - 50 years ago we had no such thing and got by just fine - modern society has got far too used to its 'conveniences' and lost the skills needed to do without them - it ain't hard to do a walk around check - it's like checking tyres or oil - people wait till a damn light comes on now - hell some cars don't even come with a dipstick - and almost none come with a spare these days.

None of todays modern marvels will survive in the same way that cars from the early 1900's have - all thanks to the microchip ...

Bypass the modules. Pay attention to the wavelength of the LED's though they aren't all equal and the plastics used are the correct colour only when they have the correct wavelength behind them - for a red lens I'd be considering a red LED not a white one ... I think somebody did a test on this with the dashboard lights but I can't recall where I saw it.

 

Spent a while on the car yesterday and I really am getting close now!

I've got the rear tail lights working with LEDS, AND with the bulb failure system working (more on this later!).

And I've got the front and rear indicators working with LEDs, AND at the right speed now. (You can change the rear ones alone and you'll keep the right speed, but change the front ones as well and they run at double speed. So it involved replacing the flasher unit).

And I've worked out the front sidelight system and how it works with the bulb failure module (confusingly it works with the current from the separate small bulbs, with or without ignition on, but not with the filaments also used for sidelight illumination in the main headlight bulb when the ignition is on).

So, still one problem to solve - the bulb failure for the brake lights. I can see me ending up bypassing this one unfortunately, because of how it works). So a polite request again - anyone got a photo showing exactly where it is on a facelift car (tucked up in the inner LH rear wing), before I start stripping out the boot strut and bracing panel?

Tks

Paul

 

Paul
On pre facelifts it is under the rear of the console; but I expect you knew this?
ON another point, I would like to change my flasher unit for a more noisy click one. ANy ideas or suggestions (not LED, just normal bulbs).

 

Hi Greg,

Tks, Yes, I was aware it was under the console and then moved to the inner rear wing on facelifts. As I just know that I'm going to end up rewiring to bypass it, I just really want to know exactly where it is via a photo before I start stripping the inner boot strut support out to find it and work on it.

As regards the flasher unit, the original one on my facelift 4 litre is definitely noisy enough for me to not only hear it, but to find it easily without any reference to the workshop manual! I don't know if anything other than the unit itself would influence the noise level? I wonder if the facelift one would work in your car and give you the noise you want?
It seems the pre-facelift uses DAC1731 & my facelift uses DAC6081. I'll take a photo of my unit later today if I get to the car.

Cheers

Paul

 

Greg - Wire a 12V piezzo buzzer in circuit - that should get your attention - and annoy the **** out of you. On some modern motors the click is fake and put through the car's audio or is done with something similar to a piezzo in the speedo binnacle since they don't use relays. My last Audi was 100% comms based with the controller in the light itself yet it still had a click - as a side story I had to get one replaced and it needed coding to the car - part of an effort to prevent cars being stolen broken for parts. Why do you need indicators anyhow - you drive a Jag - can't forget them if you don't use them - the hoi polloi should know where you are going

Using any kind of current based detection negates benefits to using LED's beyond the longevity thing, as Paul is finding, especially in the UK given that the new MOT rules in the UK require such things as bulb failure warning lights to be functional if fitted ( such BS ) - it is possible to recreate the bulb check using FET's and a dedicated LED driver but it is something of a mess about wiring wise to make it work, not to mention you need to build the module - not sure if anyone has actually made one for retrofitting to cars like ours - I did see one for caravans etc because new vans are LED lit and trailer warnings weren't working as a result, never bought one so not sure how they work.

Trailer Module
LED Driver / Failure detect chip