Trailer light troubles [Solved]

[Malakym]

I've been having problems with the lights on a small trailer - other trailers work fine so my socket is okay.

Indicators and fog work fine.
Bulbs tested with 12v work on both contacts, for side and brakes and side+brake together being respectively brighter or dimmer.
The contacts are all clean and rust free, when checking with a multimeter both tabs work to produce ~12v (brakes when pedal is pressed obviously).

The problem seems to be I can only get the side light portion working, or if I force it in against the keyed nubs - the brake lights. Both positive voltage tabs are contacting tight. Even got new fancy LED bulbs which do the same.

Any ideas?

 

[Astra99]

Bad earth? Error in connecting the cables to the light assembles? Sidelights are 58L & 58R using black and brown cables. Brake lights are on 54 using a red cable. Indicators are L & R using green & yellow. 54G is blue and is "trailer brake" but often used for reversing lights etc. Earth is on terminal 31 and is white, the cable being bigger than the other six. This is assuming you are using a standard 7-way plug/socket & cable. Check ALL the connections form the trailer PLUG to the light clusters.

Also, make sure the bulbs you are using are the correct ones. The double-filament are usually type 380 - offset pin, or V E R Y rarely 381 straight-pin, the indicators are 382 as are the reversing/fog lights.

 

[Malakym]

iring loom is a Daxra one so not custom wired so shouldn't be wrong - because of the multimeter showing good I haven't actually checked this through yet - bit dark now but will confirm next.

Bulbs are 380 type.
Standard 7 pin socket.
Indicator/Fog working to me shows earth is fine at least to the plug. The individual earths on the brake/side metal plate seem okay - the bulbs wouldn't even work half the time if this was broken?

 

[Burnerman]

Having worked on many trailers and lighting boards, I have yet to find one that didn't look like it had fallen out from a Christmas cracker, the quality is so poor. The bulbs are loose in their holders and the positive connections may or may not make the required contact. Although the connection may seem ok voltage wise, passing the necessary current is another matter.
Clean up all bulb contacts and make sure they are tight in their holders and you should get there.
John

 

[Malakym]

Will do - I've cleaned up a few in my time, normally rusted to hell. A bit of filing, clamping the ground plate and bending the tabs up normally sorts it all.

I've noticed you can buy all in one LED clusters now, instead of just retrofitting LED bulbs into the housing with is most often the problem. Tempted.

 

[Burnerman]

Any system that is waterproof would be a good start
LED's should be more forgiving, but the indicators may become upset - much can depend whether your vehicle is CANBUS or not here.
John

 

[alan333]

LED's should be more forgiving

Lots of the arctic trailers at work have LED rear lights and the mechanic reckons they fail at about the same rate as standard bulbs.

 

[Burnerman]

Interesting.....it can't be due to excess heat or glass fracture so I guess it must be vibration?
Can't say I've had any great issues - just the odd high level brake light cluster.
John

 

[Malakym]

Done some more checks - got the bench power supply out and tested from trailer plug to rear and its all okay from there (testing one at a time).

I wired up the car pins to the trailer pins with some croc clips - focusing on just the earth, tail light (RH and LH are bonded so only need RH) and brake pins.

Earth + Tail = works
Earth + Brake = works
Earth + Tail + Brake = brake works, but tail lights don't

When the brake lead is connected up (without the pedal pressed) the tail lights go out - but the brake lights work with the pedal.

I would think a short somewhere maybe but cannot figure out where that could be - and how the brake lights would work if that was the case.


Edit:

Decided to pull the socket off and test on bare wires, same issue.

So whilst I had the socket off I could pull the loom through its beam so decided to remove the clusters and wiring loom to test, and I found a damaged section.

I thought the tape was holding together the 2 wires to be tidy but it was covering some exposed wires, didn't check for shorts just assumed(!), cut behind this (luckily had enough slack), rethreaded loom, rewired socket....

...same problem

Lots of the arctic trailers at work have LED rear lights and the mechanic reckons they fail at about the same rate as standard bulbs.

A lot of LED setups either have no controller (direct drive, maybe a resistor) or a cheap controller. LEDs are cheap, controllers aren't.

 

[Burnerman]

Check for any two filiament bulbs fitted the wrong way round.....easy enough with such poor quality lamp units! Failing that, I reckon one of the bulbs isn't making proper contact with the metal holder. Are the stop lamps much brighter than the tail?
John

 

[Malakym]

I know they're the correct way as I can push them in reversed and they work(the fault) in the opposite direction.

The problem is when the brake pin is connected without being on, it seems cuts out (as if its grounded instead of open circuit) until the brake pin provides voltage.

I've messed with the holder a bit, very sure its contacting, specially since they work one way or the other.


At this point I reckon there is something wrong with the LED bulb, and a filament bulb would work - granted I replaced these as one had blown and the other was okay but acting in the same way, which is now duff.

Going to get some non-LED ones tomorrow to confirm.

 

[Malakym]

Issue solved - nabbed a neighbours mint condition light board - that works. Swapped the filament bulbs with LED and the issue followed the LEDs.

Unless there is something odd about my car wiring that the filament bulbs don't have a problem with.

Thanks for the suggestions.

 

[Astra99]

It wasn't LED bulbs for something like the BMW, which uses a single filament with two positive contacts, one for position (tail) lamp (runs at about 7-8V) , the other for brake light (runs at 12V)??? Installed in a "normal" circuit, this would throw up no end of strange problems, and possibly wreck the LEDs as well.

 

[Malakym]

I don't think so, they do work under 12v separately, it seems that the car earths rather than "opens" the circuit. We put a diode inline on the 12v brake tab on a bench supplies and it fixes the light.

Tested the LED on a new trailerboard on another car - to make sure its not my socket - same problem.

Got the new filament bulbs, put in trailer...expecting it to work... no go! Borrowed the other bulbs from the trailerboard, just one... both worked.

I ended up wiggling the socket and the lights came on when putting pressure on the plug - since the board works in my car it must not be my socket.

Took a screw driver to the pins (I had cleaned them up prior) which have splits in them and made them wider - everything works! Got someone to stand on the brake pedal and someone to watch the lights, moved the plug around like crazy and nothing goes out.

So I had a problem with the plug *AND* the LEDs I had to replace what I thought was faulty (one was visually blown though) filament bulbs!

 

[Burnerman]

You have to admit, trailer stuff is so poor quality it's hardly fit for purpose.....connections can sometimes pass the voltage but shy off at any decent current.
I find the aluminium sockets somewhat better than the plastic ones but they too are pretty poor and I replace them almost as a matter of course when they come in.
At least you've made some progress, and we appreciate the update!
John