Them dangly things behind the unit!

What colour is what ? do I need to know this if going for my class C thoery test?

Answers on a postcard usual address

thanks

Dan

Wouldn’t worry too much about colours,Dan,as they are ALL black on my unit.
It’s the connectors that you need to look at,but don’t panic as they are a different connecter for each line,so you can’t connect the wrong line,so to speak.
One tip though, when connecting the lines,always start with the "furthest " connection, then work towards yourself,then when disconnecting start with the one "nearest " to you. This saves you getting tangled up in the lines,and also your trousers will have less grease on them as a result

Dan.

It was part of the theory test & is in , or was in, the DSA book for the theory test.

PS. they are called susies.

Its in section 8 of the dsa official theory test of large vehicles!! coupling mechanisms .Got to know it all bro, im afraid,as there is no theory test for the artics, so it encompasses both types of vehicle,good luck!!

You DO need to know about air lines for your C2 (cat c) theory… Seems daft at this point, but if you think about it, you’ll never do a non-practical test again so best to know now anyway as you could take your C1 test next month…

So… IIRC…

RED - emergency brake (handbrake)
YELLOW - secondary brake (foot brake)
BLUE - Aux air line (not sure what it’s for… air suspension, rear steer or old abs…!!! )
BLACK - electrics…

The truck i’ve been practicing on this week has two leccy plugs but no abs.■■ and a connection on the trailer for the aux, but the unit doesn’t have an aux so it was left unconnected…

disconnect in order so that the RED is the last one out (so i’ve been told… )

I could be completely wrong, but i’m sure someone will know for sure…

Luv
Chrisie…

Just for reference Dan The red airline is the supply. It’s permanently charged (if you find a unit with black airlines on then it’s the one with the female end on it.

The yellow air line (or the one with the male end) is the control and is only charged when the brakes are applied. To further complicate things on some units (Daf for one) the yellow air line is charged when the handbrake is applied.

Hope your keeping up!

Just to complicate things further you normally find that on wagon and drags the male female ends have been reversed, but the colours are the same (as long as they aren’t black).

Then there’s the blue. You don’t often come across them anymore but they were the auxiliary. They had a thicker female end on them. On older trailers you will notice that there is a larger male end that is rusted up and has not been used for many years.

Basically. I wouldn’t worry too much about them. There little chance of getting them wrong. (unless there palm couplings — don’t even ask)

To be absolutely sure that you have connected them correctly make a habit of pressing the brake pedal with your hand from outside the cab when you have finished coupling. You will hear the air escape from the trailer as you release it.

Always ensure that you have given half a twist to the collars.

Hope that helps a little but if it’s confused you then don’t worry having re read it it’s left my head spinning.

Ragtop:
but the unit doesn’t have an aux so it was left unconnected…

Are you sure I can remember being told that Mercedes units were fitted with ISO sockets as far back as “L” reg. Admittedly it was tucked well away out of sight, so perhaps there is a socket fitted but no-one has thought to plug a lead into it.

Thanks for your time guys (& girlies)!

I’m on a twelve hour night shift tonight and am doing some swotting between sending ambualnces to (zb) heads!

Got the test on the 1st Dec for those of you that missed that on the previous post.

Thanks again

Super Dan

P.S. marlow that just about sums that up!!! lol

Super Dan:
I’m on a twelve hour night shift tonight and am doing some swotting between sending ambualnces to (zb) heads!

And I’m sure you’ll be contemplating Marlow’s comment

Marlow:
Always ensure that you have given half a twist to the collars

in the totally different context.

If I remember correctly, the Blue line, goes back to the days of what was referred to as the “Dead Man’s Handle”. Basically, an additional hand control that operated the front wheels of the unit and the trailer brakes. This was in the days before Spring Brakes. Whilst the Blue line survived for many years afterwards, I’ve never understood why. Except for the fact that the first portion of the Parking Brake provides a ‘Progressive Brake’ should the foot pedal control valve fail.

Over here, we only have red (emergency-always charged to keep chamber disengaged) and blue (service-actually engages brakes). You guys complicate things too much.

AlexxInNY:
Over here, we only have red (emergency-always charged to keep chamber disengaged) and blue (service-actually engages brakes). You guys complicate things too much.

Over here, we only have red (emergency-always charged to keep chamber disengaged) and yellow (service-actually engages brakes). Doesn’t seem any more complictaed than over there Alexx.

Alex
what about electrics for trailer lights and an other for ABS braking.
There is also another connection on a couple of ours for the loading lift on the back

AlexxInNY:
Over here, we only have red (emergency-always charged to keep chamber disengaged) and blue (service-actually engages brakes). You guys complicate things too much.

Hark at him now. Its only a few years since they started putting brakes on the front axle

2 line braking is common across Europe now and the blue line was discontinued many years ago along with air taps. instead of 3 air lines we jave ended up with either 4 or 5 electrical suzies

And don’t forget to put them away properly after use,especially if the vehicle has more than one driver.

There’s nothing worse than getting into a tractor unit,and then spending 15 minutes untangling the spaghetti suzies at the back of the cab.

Also,it saves them dropping into the chassis and getting wrapped around the prop shaft.

Ken.

Alex
what about electrics for trailer lights and an other for ABS braking.
There is also another connection on a couple of ours for the loading lift on the back

ABS on trailer here is self-contained, and only draws power from the lighting circuit. I have seen a few rental tractors that use a second plug, but I’ve never actually seen one in use. I believe the second plug was for auxilliary stuff.

Hark at him now. Its only a few years since they started putting brakes on the front axle

Actually, it’s been more than 20 years since front brakes have been required. It was at that time that spring-safety cannisters (one pair on the tractor and a pair on each trailer axle) has been required. However, we still use mostly crashbox trannies and drum brakes all around.

On a slightly different thread (sorry) all this talk of susies etc. reminds me of when me ‘n’ her were on holiday in the Gambia. Taking the ‘ferry’ over the river there was a old snout nosed renault with a tandem tipper on the back. So as you do I asked the driver - must have been all of 18 - where he was going etc. said he was from N. Senegal and he was going to S. Senegal and it was quickest thru Gambia.Then the ferry docked and he said he had about 28 ton of gravel on board (on 4 axles!). Rather him than me I thought and then as he drove of the boat I noticed he had only ONE line twixt truck and trailer and yes it was the one for the tipper! Definately rather him than me.