Thread: Discovery 3 LED trailer lights

Originally Posted by sniegy

Turn ON for LED lights on trailer.
Turn OFF for Normal incandescent globes so not overload the indicator circuit i can only assume.

I also have this fitted to mine.

When on the car believes a trailer is attached, even if one is not, ie the great flashing trailer appears even if no trailer attached.

Not sure if it makes a big difference though as I have forgot to turn it off a few times

One funny thing is that if you do not turn the LED module on then both your van indicators will go off at the same time when you indicate, helps you realize you forgot to turn it on when doing pre departure testing.

Just out of interest, for the D4's, what about a 22uF 16v capacitor wired to a small wattage 6ohm resistor. As the initial sense pulse is a short one off, the cap will not charge and hence current will flow for a brief period during the pulse to ground through the resistor. When the blinkers are activated the extended on time of the blinkers will charge the cap before the resistor overheats thereby stopping current flow to the resistor.
Cap charge bleed off could be handled by a 50k ohm resistor across the cap leads. Due to resistance in series being the sum of all resistances, only when the cap is discharged would high levels of current flow albeit briefly.
Year 9 electronics theory at it's best.

Seems like this might solve both the space and overheating issues of the large load resistor.

I need to wire up a Load Resistor setup for my new MY14 D4 so that the vehicle can be used with my boat trailer which has LED lights. I tow a variety of different trailers so I want the LED modification to be vehicle based rather than trailer based, and also the trailer gets dunked in the ocean so I don't want to tamper with the sealed wiring on it.

The trailer wiring appears easy enough to access, from the connector plugs inside the cover on the LHS of the cargo area. I have a couple of options for wiring in a load resistor that I need some advice on.


OPTION 1 basically placed the load resistor in parallel with the turn indicator wiring. Would this draw a load sufficient for the car to detect a trailer being connected?


If Option 1 won't draw a load, OPTION2 just wires it in series so all current goes through it. Would this place undesirable load on the trailer wiring?


OPTION 3 places a relay into the tail-light circuit that would activate then the trailer is connected and lights turned on. (I normally travel with lights on anyway.) The load resistor goes directly to ground and places no additional load through the trailer wiring. This may be over-complicating things though???

Your expertise would be appreciated...

Cheers,

Option 1 will achieve nothing as the resistance of the resistor is far greater than that of the section of wire so the current will flow along the wire, not the resistor.

Option 2 will achieve nothing because LED lights draw so little current.

Option 3 - why not just fit the load resistor without going via relay contacts? When there's no blinker power there's no current flowing through the resistor anyway.

Originally Posted by JonW

Just out of interest, for the D4's, what about a 22uF 16v capacitor wired to a small wattage 6ohm resistor. As the initial sense pulse is a short one off, the cap will not charge and hence current will flow for a brief period during the pulse to ground through the resistor. When the blinkers are activated the extended on time of the blinkers will charge the cap before the resistor overheats thereby stopping current flow to the resistor.

The low wattage resister will stop conducting because it will disintegrate/burn/catch fire from getting too hot!

I don't think your option 1 and 3 will work as the current will take the path of least resistance and bypass the resistor. Option 2 may work ok with LEDs, but with trailers with globe lights it may affect them. It's not something I've tried over the years so I've no idea how it would go in the real world.

Option 3 will still result in current flowing through the resistor. How would 2 globes light from the 1 power source otherwise?

Option2 used with incandescant globes will dull the globes and the resistor will still heat depending on how many globes are being powered, just not get as hot as if across to ground.

Originally Posted by wbowner

When on the car believes a trailer is attached, even if one is not, ie the great flashing trailer appears even if no trailer attached.



Not sure if it makes a big difference though as I have forgot to turn it off a few times



One funny thing is that if you do not turn the LED module on then both your van indicators will go off at the same time when you indicate, helps you realize you forgot to turn it on when doing pre departure testing.

By design?