Numb Thumbs
24th July 2020, 12:38 PM
I have just finished wiring up a pair of ballast resistors to my towing plug harness so I can just flick a switch and it will think it has a trailer with incandescent globes...
It turned out easier than I had feared. If you put a multi meter across the right or left pins and earth you will find that, with the ignition on, there is actually around 10.4 Volts there. This makes checking to see if you have the right wires easy. I assume this is checking to see what the resistance of the globes is.
It turns out, on my 2019 D5 5 seater Sd6, the wires to the trailer plug are actually the Australian Standard colours, which is handy as there is no way I can get the plug off to open it up and see.
I removed the tray under the false floor to get to the wiring - lucky me, no sub-woofer to take out - and unwound the black tape from the wiring bundle. There were two wires in the bundle - one plain yellow, one plain green as per the standard - which looked right, and, after stripping off a small area of insulation they proved to be the ones I needed. I soldered one wire from the resistors straight to each one. I then mounted the resistors on a section of aluminium angle as a heat sink and used a convenient bolt to attach the angle.
The other end of the resistor wires I soldered each one to one half of a piece of twin core wire and then I ran both twin core wires across the back of the car to the jack storage compartment and put a double pole / single throw switch on the end. Back at the resistors I joined the other half of the twin wires together and crimped on an eye which I attached to a convenient earthing point.
Job done.
When I flick the switch, I get the green trailer lights flashing with the indicators. Flick it again, no green trailers. Unfortunately, I can't test it with our camper attached as we are in lockdown...
Cheers
Numb Thumbs ;)
PS Thanks to Graeme and Hugh Jars for their help!
It turned out easier than I had feared. If you put a multi meter across the right or left pins and earth you will find that, with the ignition on, there is actually around 10.4 Volts there. This makes checking to see if you have the right wires easy. I assume this is checking to see what the resistance of the globes is.
It turns out, on my 2019 D5 5 seater Sd6, the wires to the trailer plug are actually the Australian Standard colours, which is handy as there is no way I can get the plug off to open it up and see.
I removed the tray under the false floor to get to the wiring - lucky me, no sub-woofer to take out - and unwound the black tape from the wiring bundle. There were two wires in the bundle - one plain yellow, one plain green as per the standard - which looked right, and, after stripping off a small area of insulation they proved to be the ones I needed. I soldered one wire from the resistors straight to each one. I then mounted the resistors on a section of aluminium angle as a heat sink and used a convenient bolt to attach the angle.
The other end of the resistor wires I soldered each one to one half of a piece of twin core wire and then I ran both twin core wires across the back of the car to the jack storage compartment and put a double pole / single throw switch on the end. Back at the resistors I joined the other half of the twin wires together and crimped on an eye which I attached to a convenient earthing point.
Job done.
When I flick the switch, I get the green trailer lights flashing with the indicators. Flick it again, no green trailers. Unfortunately, I can't test it with our camper attached as we are in lockdown...
Cheers
Numb Thumbs ;)
PS Thanks to Graeme and Hugh Jars for their help!