Bulb failure sensor systems.

[steve-V8s]

What do the typical bulb failure sensor systems look for on a can bus car ? I get the impression that they will report a failure even if the lamps are off so presumably they poll the lamp to see if it offers the appropriate resistance. The resistance however would plainly be considerably different when the filament is cold. Does it look for a load applicable to the specific bulb or just “a load”

Would like to fit an LED replacement reversing lamp but don't like the cost of the “CAN Enabled” ones which are presumably an LED with an added load resistor.

[GreenV8S]

steve-V8s said:

the “CAN Enabled” ones which are presumably an LED with an added load resistor.

Yes, I believe that's all they are: an LED lamp, with a parallel resistor to bring the overall current flow up to match the original spec incandescent bulb. I don't see why you couldn't provide the resistor yourself - if you know the current rating of the original bulb and the LED it should be easy to work out what resistance is needed. It'll probably need to dissipate several Watts of heat which means it will need to be quite large, so you need to consider that in your price comparison.

[steve-V8s]

A resistor which presents the same load as the lamp would probably keep the system happy but a resistor capable of 21 W is going to be physically much bigger than the lamp and will produce 21watts of heat that will need dissipating somewhere. The CAN enabled ones plainly don’t have a large enough resistor for it to be a simple as that.

[GreenV8S]

The original incandescent lamp obviously dissipated the same amount of heat, so the LED assembly plus resister should be able to do the same without any additional external heat sink etc, as long as the resistor is thermally connected to the assembly.

ETA: A quick Google suggests that some people selling LED laps also offer separate 'CAN compatibility' optional wiring kits which consist of a resistor wired in parallel with the lamp, complete with those nasty scotch lock connectors.

Edited by GreenV8S on Wednesday 18th January 18:09