Thread: Discovery 4 - zero lights on any trailer

Originally Posted by Geedublya

Because if you put in the resistor (1 only) the car knows it has a trailer and modifies the appropriate programs (gearbox, ABS, trailer stability, rear parking sensors, rear camera etc) to compensate.
Mine asks if you have connected a trailer and then asks you to set up a whole lot of parameters such as length from drawbar to axle, number of axles, weight etc. It would appear that it takes these parameters into consideration when modifying the various programs.

Hey Guys :-)

Long time reader but First time poster from AKL, New Zealand. I bought my 2011 TDV6 brand new in Perth and a couple of years later I shipped it back to NZ when I returned home.
I do a lot of towing and my trailer has LED lights. As far as I know the trailer LED's work fine as it passed it's yearly WOF (Warrant Of Fitness). This new trailer is only 2 months old.

Now, I don't get the "Tow" icon in the dash and my rear sensors don't go off which is annoying.

The way I understand it that the car is looking for a 21W globe etc (resistance) in one of it's indicator circuit so if I was to put a 6.8 Ohm resistor (or as near as possible to it) in parallel with one of the indicators that should activate the dash trailer icon and turn off the rear sensors etc???

If we have:-

21W Globe (normal wattage for an trailer indicator bulb)
12V Power Circuit

Then we can work out the resistance...

Ohms Law = V/IxR

and....

I = P/V

Then....

21W/12V = 1.75A

Therefore....

12V/1.75A = 6.8 Ohms

Is somebody able to confirm please if this would fix my dash Trailer Icon and reversing sensor issue?

I've read on other sites about "magical" boxes that fit in series with the trailer wiring to fix this issue, but what I've read it's a simple fix?

I'm sure it's only the D3 that sends a pulse, therefore requiring a relay?

Thank you so much guys.

Stevie B :-)

Originally Posted by StevieB

Hey Guys :-)

Long time reader but First time poster from AKL, New Zealand. I bought my 2011 TDV6 brand new in Perth and a couple of years later I shipped it back to NZ when I returned home.
I do a lot of towing and my trailer has LED lights. As far as I know the trailer LED's work fine as it passed it's yearly WOF (Warrant Of Fitness). This new trailer is only 2 months old.

Now, I don't get the "Tow" icon in the dash and my rear sensors don't go off which is annoying.

The way I understand it that the car is looking for a 21W globe etc (resistance) in one of it's indicator circuit so if I was to put a 6.8 Ohm resistor (or as near as possible to it) in parallel with one of the indicators that should activate the dash trailer icon and turn off the rear sensors etc???

If we have:-

21W Globe (normal wattage for an trailer indicator bulb)
12V Power Circuit

Then we can work out the resistance...

Ohms Law = V/IxR

and....

I = P/V

Then....

21W/12V = 1.75A

Therefore....

12V/1.75A = 6.8 Ohms

Is somebody able to confirm please if this would fix my dash Trailer Icon and reversing sensor issue?

I've read on other sites about "magical" boxes that fit in series with the trailer wiring to fix this issue, but what I've read it's a simple fix?

I'm sure it's only the D3 that sends a pulse, therefore requiring a relay?

Thank you so much guys.

Stevie B :-)

correct, but just go and get the resistor from your local auto parts store or equivalent. They should have something like this :

LED Load Resistor - Products - Narva

Stick it in parallel with the trailer lights.