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Freetrack/XL LED bulb replacement?
- Thread starter MrDurst
- Start date
CAN bus lamps
If you are thinking of saving power by using LEDs, forget it.
The CAN bus system will flag up a fault if a lamp is taking significantly less power than the system thinks it should. One way round this is to add additional load to the circuit in the form of an external load resistor connected across the lamp in question.
For example.
Suppose the number plate lamps are 6 watts each and there are two of them ie 12 Watts in total,and suppose the LED lamps that you want to replace them with are only 2Watts each then you have to dump the remaining 8 watts into a load resistor.
The value of the resistor can be calculated from the formula R=V x V/W (Voltage squared divided by Watts) In the above example, for a 12 Volt system R=144/8 which is 18 Ohms. So you would be looking for a 10 Watt 18 Ohm resistor to wire in parallel (across) the number plate circuit.
There are lots to choose from on Ebay and there are even some with wires attached specially for CAN bus circuits.
One example that can save you about £40+.
CAN bus HID lamps cost around £65-70 per pair.
Standard HID lamps are £25-30
Wire in 25 Watt 7.5 Ohm or 8.2 Ohm resistors (Nearest preferred value) costing about £1.50 each + p&p. and save yourself £40.00
Note that the resistors should always be fitted across the 12V feed to the HID components, NEVER across the lamp itself.
If you are thinking of saving power by using LEDs, forget it.
The CAN bus system will flag up a fault if a lamp is taking significantly less power than the system thinks it should. One way round this is to add additional load to the circuit in the form of an external load resistor connected across the lamp in question.
For example.
Suppose the number plate lamps are 6 watts each and there are two of them ie 12 Watts in total,and suppose the LED lamps that you want to replace them with are only 2Watts each then you have to dump the remaining 8 watts into a load resistor.
The value of the resistor can be calculated from the formula R=V x V/W (Voltage squared divided by Watts) In the above example, for a 12 Volt system R=144/8 which is 18 Ohms. So you would be looking for a 10 Watt 18 Ohm resistor to wire in parallel (across) the number plate circuit.
There are lots to choose from on Ebay and there are even some with wires attached specially for CAN bus circuits.
One example that can save you about £40+.
CAN bus HID lamps cost around £65-70 per pair.
Standard HID lamps are £25-30
Wire in 25 Watt 7.5 Ohm or 8.2 Ohm resistors (Nearest preferred value) costing about £1.50 each + p&p. and save yourself £40.00
Note that the resistors should always be fitted across the 12V feed to the HID components, NEVER across the lamp itself.
There are people on this forum who have done (on Leon or Altea) number plate and interior with LED festoon replacements. And also reversing and rear fogs with super bright CREE LED's. However, the back/brake and rear indicators cannot be modified.
It seems that not all of the lamps are monitored by the CANbus system. It would be good to know which are and which are not. (List anyone)? I'm not up to speed yet on CANbus monitoring unfortunately.
It seems that I chose a bad circuit to use as an example of the calculations but the principle applies to all CANbus monitored circuits however.
It seems that I chose a bad circuit to use as an example of the calculations but the principle applies to all CANbus monitored circuits however.
I posted a YouTube vid of a German Altea fitted with rear LEDs. I'm guessing they were modded Golf Plus/Passat type arrays. If the feed for tail lights was taken off the numberplate lights, that would leave brakes to run off the existing feed. There was some VAGCOM data about that detailed how various cars had to be set up for different lights.
It's probably a royal pain to do, but it's certainly do-able.
It's probably a royal pain to do, but it's certainly do-able.
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