Fitting LED lights to trailer - they don't work!! Enlighten me.

[Colin Lindsay]

I cannot get my head round this one so am asking 'those in the know' to hit me a slap and tell me the birds and bees of LED lights.

I bought LED lights for my trailer (and a huge set for the horse trailer) - neither work when plugged into the Freelander or the Mondeo when I had it. Ordinary bulbs work fine.

Now: if I link the two sets, bulb and LED, they both work. One cable leaves the trailer connector, splits in a junction box, one end to a pair of bulbed lights and the other end to the LED units. The lights all work except the bulbs are a nightmare, always needing adjusted or replaced as they blow or the terminals get dirty from living outdoors.

I can't get my head round the electrics of the Freelander in that it 'doesn't sense' the LEDS - it's an electric cable, power should flow down it regardless of what's at the other end. I've read all sorts of stuff today about resistors etc but it cannot be so difficult that I have to individually wire a resistor into the line for each bulb and worry about it overheating etc as some of the how-to's claim.

Surely there has to be a simpler solution? Someone please enlighten me.

[PeteH]

Mystifying?, I have changed ALL the interior lights in the Motorhome with absolutely no problems. (my) Only theory is that the LED`s are not being recognised by the "canbus" controller on the freelander?, which would be setup resistively to suit the higher resistance of the Bulb`s. Adding the no LED`s, would to my, limited experience/knowledge increase the overall resitance to a level the canbus controler can recognise. IF, my theory is correct, then the only solution is to find a Trailer canbus controler which is specifically setup for LED`s?

Pete

Edited September 2, 2023 by PeteH

[johny]

The electronics that supply the lights look at the resistance of the circuit and if not within parameters wont power it, normally giving an alarm such as blown bulb. This system also protects the electronics from overload if trying to supply a short for example.

By running bulbs in parallel with the LED the circuit resistance is REDUCED to within the correct range and of course you could achieve the same by installing appropriate resistors instead of the bulbs. Be aware though that any resistors used not only have to be the right resistance but also rated to dissipate the heat generated.

I think LED are offered by suppliers on ebay and elsewhere incorporating a resistor so they can be used in Canbus systems...

[PeteH]

There appears to be "Programable" Canbus controllers "out there" by the look of it?.

(https://www.avionitech.com/en/controller?gclid=Cj0KCQjwusunBhCYARIsAFBsUP-DTtH0O7fdi9IvaRrkoLmAZsr3ujJUdMNseVS73gCV8s2ruDKGyGgaAh6UEALw_wcB)

I assume the issue would be in determining the correct device for your specific aplication?.

Pete

[thescrapman]

You can get voltage sensing units that then switch the trailer lights, so should be unaffected by LED lighting.

Wire it to the lights in the car, rather than use the CANBUS system.

[Colin Lindsay]

I have a second trailer, a Daxara model - this one has LED lights and works no problem with the Freelander, just plug and play. I've had it upside down and traced the lights all the way along, but no visible resistors or any other kind of electric gadget different to my other setup. Definitely headscratching. I may just need to find light units that have built-in resistors?

[PeteH]

I`m begining to suspect the issue is with the LED light set?. Maybe from another source they may function?.

Pete

[JohnD]

Has it been mentioned that LEDs have polarity?    They must be connected the right way around, +/- wise.

A multimeter, cheap as chips, will confirm that volts are getting to the wires, and which way round they are.   Between wire and earth shows voltage = +ve,    between wire and earth shows nothing shows -ve.  OR not working! 

John

[PeteH]

Oooop`s. Forgot that LED`s are indeed in the majority Polarity sensitive. But I have G-4 LED`s in the Motorhome which will work in either orientation.

Pete

[JohnD]

In my ignorance, what's a "G-4 LED"?

[PeteH]

1 hour ago, JohnD said:

In my ignorance, what's a "G-4 LED"?

G-4 Capule Bulb`s. I replaces many of the Halogens in the M-H with them.

Pete

[JohnD]

Half work in one direction, half in the other?

[Wagger]

2 hours ago, JohnD said:

Half work in one direction, half in the other?

That's correct JohnD. In the early years we used red one way, green in reverse and a.c. gave a third colour all behind a diffuser. Then the manufactures built it all in one two wire device.

Edited September 3, 2023 by Wagger

[JohnD]

The gods' teeth! What waste!  Double the number of diodes, plus extras to direct the current in the right direction, all to compensate for humans' incompetence!

John

[johny]

To be fair though, surely if youre replacing an incandescent bulb sometimes theres no easy way to know the correct orientation for a LED in an existing holder...

[JohnD]

Quote " no easy way to know the correct orientation"

Oh, come on!    As I said above, a multimeter (one of the cheapest and most useful bits of kit!) will show you, or a test bulb!

Try between one wire and earth, multimeter shows battery volts, OR the bulb lights up, that's positive.  (Unless you have positive earth!)    If no volts, or no light, that's negative

I'm an electrical numpty, and even I know that.

John

[johny]

yes but some people just want to buy a bulb and plug it in. They wouldnt know what a multimeter was and anyway in some bulb holders youd have a job to get the prods in or risk shorting the contacts if you did. The manufacturers have to cater for the lowest level customer and as we know that can be pretty low😂

[JohnD]

But johnny, this is the site of the TSSC, an club for classic car enthusiasts, not for Sunday drivers.    And with the needle probes that all multimeters come  with you can probe the back of the light fitting!

There is no excuse.   Either you are competent or you are not.  No blame if you are not, the spectrum of ability is wide.

John

[johny]

Ha yes we can do it but the manufacturers dont make their LED just for us - wouldnt be very profitable if they did!

[Wagger]

Filament lamps run much hotter than LED's. If you get condensation, they can evaporate it quite quickly. However, the heat aids corrosion. Many units now are NOT interchangeable without adding 'Modules'. I suppose that filament lamps will become scarce as time progresses (as with household stuff), so stock up now or be prepared to 'Fiddle' in the future.

[Colin Lindsay]

2 hours ago, Wagger said:

Filament lamps run much hotter than LED's. If you get condensation, they can evaporate it quite quickly. However, the heat aids corrosion. Many units now are NOT interchangeable without adding 'Modules'. I suppose that filament lamps will become scarce as time progresses (as with household stuff), so stock up now or be prepared to 'Fiddle' in the future.

LED bulbs I don't mind, as if you go for the correct version they're a straight swap for filament versions. However the filament bulbs on the trailer require frequent replacing, or contact cleaning due to moisture - the trailer lives outdoors and is always used for carrying the horse products, manure and shavings, but literally once a week I have to unscrew the light covers and either jiggle the bulbs or else clean the contacts before they'll work, or else the bulb has just blown. Similar bulbs in the car last years, the trailer is every month, hence the interest in LEDs. I could live with LED bulbs that require the occasional clean, but had hoped that the LED units would be a fit-and-practically forget solution.

[Peter Truman]

My LED experience with the daughters Spit Mk2 Indicators, nearly 20 years ago for safety ie extra brightness I fitted LED's to the rear indicator's and the original Bi-metallic mech flasher worked OK, later on I changed the front too, the indicators didn't work as there was no load/resistance so I had to fit an electronic flasher can. I subsequently fitted a Lucas 4 way emergency flasher unit the push/pull type with it's own small rectangular Bi-metallic flasher can incorporated into the assembly that all works OK, the flasher rate is fast enough, so obviously the 4 LED's generate enough load.

Similarly my Mk2 Vitesse, but the indicators work with front and rear LED's with the old style Bi-metallic mech flasher can, so where is the extra load coming from, all electrical male bullets on both cars have been cleaned and replaced as necessary and all female joiners replaced too, figure that one out, could it be the extra wire length front to rear, or the earth continuity isn't as good relying on the chassis bolts between the front and rear of the car, the battery is fitted in the boot??

[ahebron]

As has been mentioned modern vehicles need a certain amount of resistance for the electronics to liven the circuit on even though you have operated the switch. Some cars even need the software to be activated if you decide to fit a towbar and this is often only available from the dealer due to vehicle stability control and braking changing when a trailer is used. The days of DIY trailer plugs are rapidly disappearing. 
My VW Amarok will not activate hill descent control when I have the trailer plugged in, so off road with the trailer  I will unplug the lights if needed. Obviously, when towing a trailer you do not want it to try to overtake while hooked up so this is then dependent on the skill of the driver to keep the trailer behind the vehicle when using hill descent control. It is just a loop in the socket between 2 pins but I believe a deliberate action of unplugging is safer than permanently bridging it out.
I fitted a LED reversing bulb and needed to add a power resistor to the circuit to stop the bulb fail warning. 
You can buy resistor boxes to go between the trailer plug and car socket.

Peter Truman did you use identical bulbs in your daughters Spitfire and your Vitesse?

LEDs also operate faster than filament bulbs and in brake lights the fractions of a second can mean the difference between a following car hitting you or not, yes it sounds crazy but have a read here.
https://chemistry.beloit.edu/BlueLight/pages/hp/an1155-3.pdf
https://arxiv.org/pdf/2010.10584.pdf

 

[Peter Truman]

1 hour ago, ahebron said:

As has been mentioned modern vehicles need a certain amount of resistance for the electronics to liven the circuit on even though you have operated 

Peter Truman did you use identical bulbs in your daughters Spitfire and your Vitesse?

 

 

Never thought that LED's could/would be different, like bulbs I assumed a bulb of a certain rating were the same, in answer all LED's brought off ebay at different times and sources.

I was thinking of buying new modern LED's for the Spit as there now 20 years old on the basis the modern ones could have better performance, but maybe it won't be worth the potential upgrade in performance, maybe Dad's motto of "if it ain't broke don't try to fix it"! pity he didn't follow his own rule "do as I say not as I do"!

[Wagger]

Filament bulbs have a very low resistance when cold and this increases with temperature. It make them relatively slow to gain full brightness. LED's glow faster and the current is nothing like as high. Sometimes this current will not keep contacts clean. The switch in my hall light is always oxidising over, so I leave it on permanently.

I would hardwire resistors of the correct wattage and fit LED's, time permitting.