CLS LED puddle/boot lights - canbus?

[Aaron-P85]

So I've gotten 6x 39mm festoon 6 led bulbs 12v 5w, same as OEM, just LED... And replaced the four under door puddle lights fine, below is a comparison .. Hopefully it's obvious which door has the LED.

Anyway... I changed the boots light and it comes on for a second, then off for a second repeatedly..... So I tried with the light on the tailgate part.... Same thing. No warnings on the dash?! So the only conclusion I can come up with is that they're wired into the same power supply as the canbus items but not tied into the warning system?

Can anybody confirm this before I buy the more expensive error free items?

 

[miro]

Lights are never part of the CANBUS.

What you are noticing is that Mercedes has downgraded the detection software to ignore trivial convenience errors. Especially since most of the current cars are fitted with LED lights.

When connected to a diagnostic the errors show up but not in the cluster. This reduces the number of visits by clients to the workshop during the warranty period.

 

[Aaron-P85]

I thought the licence plate, and side/braking lights were on the canbus circuit to notify of blown bulbs?
So how can I get round this on/off flashing the LED's do in the boot?

Regards
Aaron

 

[lexman8]

The puddle lights are not monitored for bulb failure so they'll work fine with standard LEDs.

I'm pretty sure all the rear lights are monitored so what's happening is that when you fit an LED bulb, the bulb controller thinks that bulb has failed (because LEDs have a much higher resistance than a filament bulb) and turns off power to that bulb. After a second or two it tries to power the bulb on again, it lights briefly but then the high resistance detected causes the controller to turn it off again. This cycle repeats endlessly.

So-called CANBUS compatible LEDs have a resistor in parallel with the LED itself that allows extra current to flow and fools the bulb controller into thinking it's okay. Whether or not a CANBUS LED bulb will work is down to the bulb itself and the sensitivity of the monitoring system on a particular car. Some combinations work, some don't.

As an aside, it's not the CANBUS that monitors the bulbs directly, it's the SAM units/lighting controllers which then send status messages over the CANBUS for action/display. The CANBUS is simply a data bus that connects most of the electrics/electronics together within the car to allow data exchange. Most cars will have 2 buses, one for critical functions (engine management, brakes, etc) and one for convenience functions (heating, aircon, etc).

 

[Aaron-P85]

Excellent explanation fella!!
So I'll buy one 'error free' light to see if it works, hope so because the puddle lights have made a wonderful difference!

 

[miro]

Excellent explanation fella!!
So I'll buy one 'error free' light to see if it works, hope so because the puddle lights have made a wonderful difference!

The R230 SL had one light connector in the armrest which was identical to the nearby canbus connector. You are correct in stating that canbus will make a lamp flash.

 

[lexman8]

...the puddle lights have made a wonderful difference!

I'd like to replace my puddle lights with LEDs. Yours look nice and bright; where did you get them?

 

[Aaron-P85]

HERE Fella, I have these in all four doors and work perfectly, that image is a little over exposed on the LED side of things, making it look a little brighter than it is in real life but not too much!