Trailer light blinking

[fourteen8]

I was picking up my friend and his family. I unfolded the rear seats and realize after that the trailer light blinking when us the indicator either left or right.

Did I hit something by mistake or sensor fault or something?

Anyone can tell me how to switch it off?

Mine is D4 2014 Sdv6


Thanks

[DiscoJeffster]

I was picking up my friend and his family. I unfolded the rear seats and realize after that the trailer light blinking when us the indicator either left or right.

Did I hit something by mistake or sensor fault or something?

Anyone can tell me how to switch it off?

Mine is D4 2014 Sdv6


Thanks

Assuming you don’t have a trailer attached, look for a switch in the rear cargo area. Someone has probably installed a trailer resistor setup to tell the car there’s a trailer attached for when the trailer has LED lights (car can’t detect the trailer in that case). You may have accidentally flicked the switch and enabled it to think a trailer is attached.

[fourteen8]

Assuming you don’t have a trailer attached, look for a switch in the rear cargo area. Someone has probably installed a trailer resistor setup to tell the car there’s a trailer attached for when the trailer has LED lights (car can’t detect the trailer in that case). You may have accidentally flicked the switch and enabled it to think a trailer is attached.

Yes no trailer attached.

Ok. I will check tomorrow morning for the switch. How come the car cannot detect if there is trailer attached? My D2 can detect if there is a trailer attached

Thanks

[RANDLOVER]

Yes no trailer attached.

Ok. I will check tomorrow morning for the switch. How come the car cannot detect if there is trailer attached? My D2 can detect if there is a trailer attached

Thanks

The car can't detect a trailer with new low resistance LED lights, hence the extra switchable resistor.

[BradC]

The car can't detect a trailer with new low resistance LED lights, hence the extra switchable resistor.

Whilst seemingly accurate, to try and elaborate a bit : LED's are a "high resistance" compared to a bulb. The cars are designed to detect a trailer by the current consumption of the indicators.

On the D3 it tests frequently (many times per second). On the D4 it tests when the drivers door is opened and closed. Compared to a 21W indicator bulb, a LED draws bugger all current, so an additional load resistor is required to make the car detect a trailer. On the D4 I believe it's only required on one Indicator. On the D3 it's a bit more complex.

Some people install the load resistor in the car and connect it to a switch that they turn on when they have a LED trailer attached. If the trailer isn't attached and the switch is turned on, the car still thinks there is one present, causing your issue.

Your D2 detects the trailer in a similar but more agricultural manner. Put a LED only trailer on and it won't know unless you have the same load resistors. On the D3/D4 it also disables the rear park sensors and changes the shift points (if you have a slushbox). I can't comment on the smarts the D2 may or may not contain because we've only owned a D1 and D3 and both had/have 3 pedals.

[Briar]

Whilst seemingly accurate, to try and elaborate a bit : LED's are a "high resistance" compared to a bulb. The cars are designed to detect a trailer by the current consumption of the indicators.

On the D3 it tests frequently (many times per second). On the D4 it tests when the drivers door is opened and closed. Compared to a 21W indicator bulb, a LED draws bugger all current, so an additional load resistor is required to make the car detect a trailer. On the D4 I believe it's only required on one Indicator. On the D3 it's a bit more complex.

Some people install the load resistor in the car and connect it to a switch that they turn on when they have a LED trailer attached. If the trailer isn't attached and the switch is turned on, the car still thinks there is one present, causing your issue.

Your D2 detects the trailer in a similar but more agricultural manner. Put a LED only trailer on and it won't know unless you have the same load resistors. On the D3/D4 it also disables the rear park sensors and changes the shift points (if you have a slushbox). I can't comment on the smarts the D2 may or may not contain because we've only owned a D1 and D3 and both had/have 3 pedals.

I think you'll find that LED's are very low resistance, not high. This is why you may need to add a load resister in the circuit to enable the trailer detect feature. With a D4, the "detection" signal is sent down the indicator circuit at door opening and also when either indicator is used, (as I'm led to believe). For my van, which uses a 12 pin flat plug, I made up a small "dongle" that plugs into the unused 12N round socket. It's a 12N plug, a bit of polypipe and 2 load resisters wired up to the 2 indicator circuits. Just plug itin when towing van. Works a treat.

[DiscoJeffster]

I think you'll find that LED's are very low resistance, not high. This is why you may need to add a load resister in the circuit to enable the trailer detect feature. With a D4, the "detection" signal is sent down the indicator circuit at door opening and also when either indicator is used, (as I'm led to believe). For my van, which uses a 12 pin flat plug, I made up a small "dongle" that plugs into the unused 12N round socket. It's a 12N plug, a bit of polypipe and 2 load resisters wired up to the 2 indicator circuits. Just plug itin when towing van. Works a treat.

No he won’t. He is completely correct. They are high resistance. This is why LED use less current than an incandescent bulb for the same lumen output, and why you apply a load resistor to simulate an incandescent load.
Try it for yourself. Go and get an led and compare it to a filament globe on your multimeter.

[Briar]

No he won’t. He is completely correct. They are high resistance. This is why LED use less current than an incandescent bulb for the same lumen output, and why you apply a load resistor to simulate an incandescent load.
Try it for yourself. Go and get an led and compare it to a filament globe on your multimeter.

Mea Culpa. You are correct. My apologies to Brad. Learn something everyday.

[BradC]

Mea Culpa. You are correct. My apologies to Brad. Learn something everyday.

Actually, you are/were correct if we take the definition of a LED as just the diode. They have a characteristic voltage drop and will happily take all the current required to pull the supply down to that voltage until the magic smoke escapes. They are used in an assembly with a current limiting device (a regulator or resistor commonly) which reduces the current to that which the LED won’t pop. As they are not actually an ohmic device, the terms low and high resistance don’t really apply, but if you think of it from the perspective as on a constant voltage, the lower the load resistance the higher the power draw. A led assembly draws considerably less than a 21W bulb, so the bulb presents the equivalent of a lower load resistance.

Regardless of the electrons, the car detects the trailer indicator by measuring the current the bulb draws. Same way it knows there is a bulb out.

[fourteen8]

Found the switch and all good now. Thanks for all the response

[Jeffoir]

Just read this thread and wanted to say I’m very proud to be part of a forum that can help member, so quickly, so thoroughly and with lots of technical info.
Also reminded me about “Ohm’s Law” along the way.
Well done everyone.
best wishes.
jeffoir.

[glenn20869]

Hi brains trust,

While we're talking about led load resistors and using them to get the car to register that a trailer is attached... I'm wondering if anyone has ever wired them into the trailer running lights rather than the indicators. I always have my running lights on so was thinking that allow me to get away with just the one set of load resistors.

Also for my education, if the resistors are connected to the indicators, do you have to use the indicators first to get the car to register the trailer?

Cheers

[veebs]

Hi brains trust,

While we're talking about led load resistors and using them to get the car to register that a trailer is attached... I'm wondering if anyone has ever wired them into the trailer running lights rather than the indicators. I always have my running lights on so was thinking that allow me to get away with just the one set of load resistors.

Also for my education, if the resistors are connected to the indicators, do you have to use the indicators first to get the car to register the trailer?

Cheers

Howdy,

If you have a D4, you only need one resistor - pick your favourite indicator, and add to that circuit :). No idea if adding to the running lights will work.

I believe the system does a test when you open the driver door, but not certain. I tend to use the indicators right after connecting anyway, as a check to make sure the trailer lights are working correctly.

[kelvo]

Hi brains trust,

While we're talking about led load resistors and using them to get the car to register that a trailer is attached... I'm wondering if anyone has ever wired them into the trailer running lights rather than the indicators. I always have my running lights on so was thinking that allow me to get away with just the one set of load resistors.

Also for my education, if the resistors are connected to the indicators, do you have to use the indicators first to get the car to register the trailer?

Cheers

It has to be on the indicator circuit(s).

As Veebs said to get the D4 to recognise a trailer is attached only one resistor is required, but if you want the dash trailer symbol to flash when you indicate you need two resistors. One on each of the trailer indicator circuits.

[Briar]

Hi brains trust,

While we're talking about led load resistors and using them to get the car to register that a trailer is attached... I'm wondering if anyone has ever wired them into the trailer running lights rather than the indicators. I always have my running lights on so was thinking that allow me to get away with just the one set of load resistors.

Also for my education, if the resistors are connected to the indicators, do you have to use the indicators first to get the car to register the trailer?

Cheers

I made a small dongle that contains 2 load resistors. When the van is plugged in the 12 pin flat, I plug the dongle in the now unused 12N round socket. Small length of appropriate size poly pipe, a 12N plug and resistors wired up. Been using this system for 6 years.
180569

[veebs]

I made a small dongle that contains 2 load resistors. When the van is plugged in the 12 pin flat, I plug the dongle in the now unused 12N round socket. Small length of appropriate size poly pipe, a 12N plug and resistors wired up. Been using this system for 6 years.
180569

It may just look bigger because it’s black, but I’m suddenly feeling rather self conscious having seen your ‘small dongle’

[Briar]

It may just look bigger because it’s black, but I’m suddenly feeling rather self conscious having seen your ‘small dongle’

It is 6", really.

[BradC]

It is 6", really.

Measured from the end or the base of the socket?

[Briar]

Measured from the end or the base of the socket?

OK, Brad, lol. I was trying to enter into the spirit of the gag.

It's actually 7" long, but not trying to brag.

170mm to be exact, total length. Easy to make. The poly pipe (from bunnings) is a perfect fit to attach to the 12N plug, I had to put a little slit on one side of the poly pipe as I put the load resistors back to back in the poly. Makes the dongle shorter than it otherwise would have been. Just wrap the whole lot in electrical tape.

180585180586

[veebs]

Well, it's certainly a solution, though i'm not sure I would want to have to explain why i needed to insert that up the back of my car whenever I wanted to tow :)

Ok, i'll see myself out...

[Briar]

Well, it's certainly a solution, though i'm not sure I would want to have to explain why i needed to insert that up the back of my car whenever I wanted to tow :)

Ok, i'll see myself out...

lol. Cheaper solution than anything commercial. At least it kills the parking sensors when van attached, which really annoy the wife when they come on. I often direct when reversing and she moves the van. Unfortunately, my wife is hopeless when giving directions.

[BradC]

OK, Brad, lol. I was trying to enter into the spirit of the gag.

So was I. Back when I was at school it was all about where the measurement was started from.... sorry, probably a bit obscure.

[Tombie]

Measured from the end or the base of the socket?

Nah. From the tip to the base of the (tow) ball(S) [emoji56]

[BradC]

Nah. From the tip to the base of the (tow) ball(S) [emoji56]

The tow ball(s) or the D3 chassisticles ?