Red air line is emergency? So if i have just the red one connected will the trailer brakes apply when braking??
Whats the yellow line used for??
Green electrical…Is this emergency? What does it do?
Black operates trailer lights?
Abs obviously operates trailer abs?
Thanks
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I’m guessing you’re a newbie
Stay safe, attach all of them 
Google is your friend
OK OK I’m being mean -
2 x electrics = Electrics to trailer for lights etc. Main one and emergency back up
2 x air lines = Brakes, suspension etc. Main one and back up emergency one. If both are the are useless you ain’'t going anywhere so be nice to them (no I’m not explaining the shunt button, stay well away)
Large black one with closure clip is, as you already said, ABS. You need that one too!
The shunt button will allow the trailers to be moved if the trailer brake is off.
Yeah i was told you can use the shunt button to shunt empty trailers around the yard but if its loaded dont touch it but connect red air line
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Red is purely there to allow the brakes to be released. If it’s attached then the brake button will release the brakes although this can be overridden by the yellow (see below).
Yellow is in charge of normal trailer braking. When you operate the footbrake or handbrake it gets charged with air and presses the brakes on just like in a car.
The black cable seems to power all the electrics, but I guess the green one powers other stuff like electronic stability etc. Never bothered to go round and find out what it actually does really (lazy git).
ABS controls both the ABS as you’d expect, but on some trailer it also runs the stability control so especially on high trailers make darned sure it’s connected!
mark1284:
Red air line is emergency? So if i have just the red one connected will the trailer brakes apply when braking??
Whats the yellow line used for??
Green electrical…Is this emergency? What does it do?
Black operates trailer lights?
Abs obviously operates trailer abs?Thanks
Sent from my iPhone using Tapatalk
Green electrical, powers fog lights and reverse lights, I believe they used or maybe still does operate the older ABS systems in trailers.
There are also some trailers which need one electrical lead instead of the 2, look similar to the EBS/ABS lead, but different colour ends.
FYI.
http://www.ratltd.co.uk/truck/pinouts/trailer/
Many electrical problems on trailers can be problems with the leads, they do get a hard life.
Depending on the type of transport operation you work for its can be handy to carry spares and a can of WD40.
First step quick spray of the connections, if that doesn’t work replace the lead, often sorts a problem and a couple of minutes to fix instead of waiting hours for a fitter to come out who’ll probably do exactly the same thing.
hse.gov.uk/aboutus/meetings/ … paper7.pdf
Red line is called “emergency” and also “supply”. It carries full pressure to supply the braking and air suspension systems.
When disconnected the trailer brakes will automatically come fully on, hence “emergency” name.
The yellow line is the “control”. The foot brake in the cab sends air down this line to the trailer relay valve to apply the trailer brakes.
For safe operation you need both air lines obviously.