I've been experimenting with LED Tail Light Bulbs for almost a year! The first set of Bulbs were much brighter than the Halogen Bulbs that came in the Car, but they turned-on my "Check Tail Lights" warning and the Turn Signals Blinked about 5 times faster than normal. So I removed them and sent them back!

Now, about 2 months ago I see an advertisement that says Lumen has made a bulb that fools the CAM Bus system and won't turn on the "Check Tail Lights" warning light......I immediately bought a set and have found that the (4) 1156 Bulbs worked as advertised (2) for Back-up and (2) for the English Fog Lights but the (4) 1157's (Brake Light warning Lights & Tail Lights) and the (2) 7507 Amber Turn-Signal Bulbs all turned on the "Check Rear Lights" warning light! So, only those (4) 1156's worked...

Somewhere along the way some one was talking about a Resistor that could be used to stop the CAM Bus effect but I can't see how they would work in our Tail Light system. The LED Bulbs look so much better and are about 3 times brighter than the Halogen one's that I really want to use them but I can't stand that "Warning Light" shining in my face all the time.....Do we have an expert Auto Electrician or someone who has solved this CAM Bus problem that we are all having?

Help!!!! Billy Clyde in Houston

 

Our cars are not actually CAN bus based, what it has is a module that detects a burnt out bulb by running the current through a low calibrated resistance (1.5ohm if I remember) and measuring the voltage drop across it.

In short, if the current isn't high enough then you will get the error message.

CAN bus bulbs have a small internal resistor, which is large enough for the marker lights, etc, but not even close to enough current to keep the tail or brake light error happy.

This is how I did it:
https://www.jaguarforums.com/forum/x...on-how-133857/

You will notice that I have left a conventional bulb in the center where it is already behind a red lens.

I would still get the very occasional error, usually just after starting the car while the alternator was putting out a bit more voltage so I added one more resistor just a few weeks ago.

It's a bit of a game to find the right resistance as it depends on the current draw from the LEDs you use, but it can be done.

 

Charlie, Thank Heavens you've answered my call! I'm about the farthest thing there is from an Auto Electronics Man but looking at your directions, I think I could do this....We have one Radio Shack left in the area and they are re-stocking it now, so maybe I can buy some of those parts from them.....The Lumen NB1156CR's and the 1156Whites work just fine without doing anything! They claim that they have added additional resistors or something like that in the base of the Bulb to stop the "Warning Light" from coming on but the other Bulbs, like the NB1157's don't work! Do you have any thoughts on what is going on with that?

Two things I'm missing is why have you continued to use the 1157 in the Regular Rear Light? What does that do? and have you hooked up the English Fog Light so it can be used as an additional Brake Light? It appears to be on in the Photo showing the Brake Lights....

Thank you again for all this information!

Billy Clyde in Houston

 

Our cars are not totally in the digital world, so the small resistors built in to the LEDs aren't enough. The circuit to detect a failed bulb caries over from the first 97MY and is more of an analog detection method.

 

Charlie, Sorry, while you were answering my question, I had gone back into the question to ask you a couple more questions!! I was editing my question at the wrong time....If you would, please check those out....Just want to know everything and it gets me in trouble some times....

Billy Clyde

 

That circuit has two bulbs in it, so the current required is higher to keep the error message away. Since it was behind a lens, changing to LED didn't look much different and leaving it means I only had to add enough resistors to make up for one LED bulb. You could put 2 LEDs if you added enough resistors.

As for the fog light, I experimented with this but ultimately left it the normal way.

 

[QUOTE=ccfulton;1743755]That circuit has two bulbs in it, so the current required is higher to keep the error message away. Since it was behind a lens, changing to LED didn't look much different and leaving it means I only had to add enough resistors to make up for one LED bulb. You could put 2 LEDs if you added enough resistors.

As for the fog light, I experimented with this but ultimately left it the normal way.[/QUOTE

Charlie, Thank you very much! I will go to work on this project tomorrow morning, as I have been trying to get this worked out now for over a year....I'm looking forward to the big update....as you probably have observed most of the newer cars out there have LED's......This past Winter I really noticed how bright they are....You certainly don't have a problem seeing them in front of you! AS the Guy said in the old forum, "maybe too bright" for him!

Billy Clyde in Houston

 

Charlie,

I was looking at the light Board and wondering....since both my Lumen NB1156's are working fine (The English Fog Light and my Back-up Light), could I get by with not putting in the resistors that go to those lights?

Billy Clyde

 

From HK via eBay you can get 20 of the resistors for $0.99, free shipping. I'm ordering 3 sets just to have spares in case I drop one (or more).

 

Fog lights and reverse lamps don't have the sensing, so no need to add anything there. Just the tail and brake lights have the current detection.

 

Charlie

Thanks again! I've told several people about your instructions and have directed several to this Thread. So you have helped many more than me!
Thank you for this!

I appreciate your help!

Billy Clyde

 

[QUOTE=ccfulton;1744292]Fog lights and reverse lamps don't have the sensing, so no need to add anything there. Just the tail and brake lights have the current detection.[/QUOTE

Charlie,

I have completed the job and only have one problem......Well! Two....I think I sent you a Private Message but I'm not sure it went through....So, this message to make sure.......

Everything works great except the Right Blinker....It works great for about 10 seconds and then starts to "fast blink" the Left one works great.....Should I add another Resistor? This does not effect my "Warning Light"...

Thanks!

Billy Clyde

 

I responded, but the short of it:
Add another resistor, the many different brands of LED bulbs on the market are not all the same resistance.

It's not like an incandescent bulb where resistance = lighting power. LEDs can have different efficiencies to produce light depending how they are manufactured.

 

Thanks so much for getting back to me with your answers and suggestions!

As you know, the LED Bulbs really light things up back there....These are Lumen NB1157CR and NB7507CA Bulbs.

With your help, now I'll be able to get this all straightened out!

Billy Clyde