When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Hi all…I’m changing the LED lights on my 93 XJS 4.0. I’ve completed the flashers with no issues and included a resistor for each (pic in attached). I’m working on the stop/tail light and plan to use 1157 LED equivalent (pic attached). Having problems:
1. Each bulb is fed by 3 wires - black (ground), red (tail) and green (stop) lights
2. When I change to the LED 1567 equivalent and plug the black and red wire in the LED the tail light comes on great. When I attached the green light wire the tail light goes out ??? (I do not have the brake pedal down)
3. I took the bulb holder and tested on bench with 12V. When I attached all 3 wires on the bench both the stop and tail lights come on ???
4. I tried splicing the resistor into the black and green lines to see if that would work but when put back in car same as in 2. above - no lights. Splicing the resistor into the black and red wires still have no light.
Not sure what is going on - works on bench but not in car ?
Any thoughts or helpful ideas would be much appreciated.
Are you putting the resistors in series or parallel with the LEDs? The 1157 equivalent LED should run on 12V and not need resistors to light properly. I am guessing that the resistors go in parallel to fool the bulb fail module with a load similar to an incandescent bulb.
Hi Paul..tks for quick reply. Sorry for any confusions:
1. I am not running any new wires. I simply replaced the incandescent bulb with the new LED 1567 equivalent but with all 3 wires attached to the bulb holder 8 get no tail light when build holder installed in car as is. If the green wire (I think this is the stop feed) is disconnected the tail light comes on. If I take the bulb holder out and test on bench with straight 12v applied to each post, both the stop and tail lights come on just fine.
2. I used the resistors for the flasher circuit to stop hyper flashing when LED installed and it works great so I thought they help with the tail/stop light issue but they dont
Hi David…I think I have it connected in parallel…I.e. one end of the resistor connected to the green (stop) wire and one end connected to the ground wire. It didn’t solve the problem
I'm a bit confused. The Stop &Tail lights are separate bulbs and separate circuits There are only 2 wires for each bulb.
From my reading of the electrical diagram, the Stop Light bulbs use a Green & Purple Feed, and a Black Earth.
The Tail light bulbs have a Red & Slate feed on the Left side, and a Red & Green feed on the Right side.
All the bulbs use a Black Earth.
If your indicators flashed fast with LEDs, you need to change the flasher relay for one that can support LEDs, not insert resistors.
You don't need resistors for any of the bulbs to work. IMHO, you really shouldn't use resistors as now you've negated one of the prime reasons for using LEDs which is to pull less current. By putting resistors into the circuit, you're now pulling as much current as with filament bulbs. And if someone subsequently swapped out a bulb for a filament bulb, you'd be pulling twice as much current which could dangerously overload the circuit.
The one problem you do have with LEDs is how to keep the bulb failure circuits working satisfactorily. And that's why many owners insert resistors, not a good answer in my view. If you find my thread on using LED bulbs, I found a way around the problem for the tail lights, by resetting the bulb failure modules. I'm still working on a solution for the Stop light circuit.
I was also a bit confused when you mentioned "inserting the wires in the LED.."? Aren't you just putting the bulbs in the relevant bulbholders? You don't need to touch or change the wires at all. Maybe show us some photos of your bulbholders in the car.
Hi Paul…see my response to each below…tks a bunch…JB
Originally Posted by ptjs1
JB,
I'm a bit confused. The Stop &Tail lights are separate bulbs and separate circuits There are only 2 wires for each bulb.
Answer: Mine has one bulb for each stop and tail light. Two filaments in each bulb so 1157 type
From my reading of the electrical diagram, the Stop Light bulbs use a Green & Purple Feed, and a Black Earth.
The Tail light bulbs have a Red & Slate feed on the Left side, and a Red & Green feed on the Right side.
Answer: Yes
All the bulbs use a Black Earth.
Answer: Yes
If your indicators flashed fast with LEDs, you need to change the flasher relay for one that can support LEDs, not insert resistors.
Answer: Yes they did. I searched and searched for the correct relay to buy but can’t find anything. A post mentioned splicing in the resistors which I’ve done and they flash perfectly now. I would definitely go the relay route if someone knows of a compatible relay to use ?
You don't need resistors for any of the bulbs to work. IMHO, you really shouldn't use resistors as now you've negated one of the prime reasons for using LEDs which is to pull less current. By putting resistors into the circuit, you're now pulling as much current as with filament bulbs. And if someone subsequently swapped out a bulb for a filament bulb, you'd be pulling twice as much current which could dangerously overload the circuit.
Answer: Great point ! This is my car so no one else will be changing bulbs. The car will be inherited by my son upon my demise and I’ll make sure as they lower me into the ground to let him know . If I can go the relay route I’ll take the resistors out…but righ5 now flashers are nice and bright
The one problem you do have with LEDs is how to keep the bulb failure circuits working satisfactorily. And that's why many owners insert resistors, not a good answer in my view. If you find my thread on using LED bulbs, I found a way around the problem for the tail lights, by resetting the bulb failure modules. I'm still working on a solution for the Stop light circuit.
Answer: I’ll try and dig it up
I was also a bit confused when you mentioned "inserting the wires in the LED.."? Aren't you just putting the bulbs in the relevant bulbholders? You don't need to touch or change the wires at all. Maybe show us some photos of your bulbholders in the car.
Answer: Sorry about that as I confused. I did just that and left bulb holders in the car with car wiring. I then just changed the incandescent bulb with the LED bulb and got nothing. So I disconnected the feed wires to see what was going on. When the red/slate feed was connected I got the LED tail light to come on. When I connected the green and purple feed wires the tail light went off 🤔
I owe you a huge apology for confusing you! Yes, our cars do use twin filament bulbs for the Stop / Tail light! I should have gone and checked my car rather than relying on a poor memory!
So, going back to your original problem, I'm not sure why the bulbs didn't work properly when you first inserted them? I've not heard of anyone who's replaced filament bulbs with LEDs on their XJS and they've not just worked fine.
If I was you, I would remove any resistors that you've inserted in the Stop / Tail light circuit and put the original bulbs back in. Then turn on the side lights and confirm they are working fine. Then replace the bulb on one side with an LED bulb and recheck that the side lights illuminate on both sides of the car. If the LED sidelight doesn't work, measure the voltage with the light switch on at the feed wire, (the Red / Slate wire, if you're measuring the left, or the Red / Green wire if you're measuring the right). Assuming you see 12v on that wire, if the LED isn't illuminating, I'd politely suggest you might have a bulb compatibility problem. Inserting a resistor to pull more current is just not the right answer.
As regards your indicators, there are lots of places selling suitable flasher relay units that can handle the lower current draw. A simple google search will find plenty. If you get stuck, Gil Keane in the UK at Better Car Lighting can provide one for the XJS. See here: Quicksilver Automotive You really don't want resistors increasing the current draw to get around the problem.
My apologies again for misleading you over the bulb types!
1993 Facelift XJS LED Light Change Question ??
. If I can go the relay route I’ll take the resistors out…but righ5 now flashers are nice and bright 
