FL2 Trailer Lights Sense Unit - senseless?

Towbar electrics used to work fine (2 years ago) but on testing with two different trailer setups today .. nothing.
Went right back to the Trailer Control Unit (the box behind the trim) that takes CANBUS in and then drives the appropriate conenctions down to the trailer socket.

Question: Does anybody know what lights/connections on the trailer it needs sense before it starts working?
It certainly doesn't see the trailer lights as connected (no indicator failure tell tail on the dash, or disabling reversing sensors)

So my guess is that unless the Control Unit senses a trailer connected it Doesn't drive power to the trailer lights. SInce none are currently being driven .. but the 12v supply in is good. hence the question

If for some reason the ECU was re-programmed without the trailer option, would any of the trailer lights work?

Thks

Andy

I vaguely recall that some sockets are fitted with a microswitch which activates when the plug is inserted. this then provides the relevant information that something is connected.

I have seen in the past that this microswitch was used to cut out the vehicle foglights when trailer/caravan connected to avoid back glare in the rear view mirror

That was the 'traditional' way of doing things. Now I believe the magic Trailer Control Module detects current flowing (or not) and advertises the fact over the CANBUS. So that the little trailer dash indicator illuminates and the reversing module is disabled along with the rear fog lights.

Every year the same thing for me but is usualy the trailer connectors see below but I did have a connector that is in the boot come apart after the rear lights had been worked on.


Check for good earth on pin 3


If its the"N" or "S" type check for corroded connections back and front they a very prone to water ingress 13 pin Euro are only slightly better.

Also check for faulty pins and sockets caused by pulling the connectors up and down to remove, the split pins close up and the sockets open up. I give them a squirt of wd40 before I put the cover on and then again just before I use the caravan.


I recommend the use of soft plastic covers for both the plugs and sockets as these help to keep them cleaner, available from caravan and trailer spares


'N' type

Yellow L/H indicator
Blue Fog light
White Earth
Green R/H indicator
Brown R/H tail / side light
Red Brake lights
Black L/H tial / side light

'S' Type

Yellow Reversing Light
Blue Ignition 12V supply
White Earth
Green Continuous 12V supply
Brown Spare
Red Fridge
Black Spare


13 pin euro

There are 3 different colours listed for all the different wires we are aware of, we do not garentee we cover all available wires.

Pin no Colour1 Colour 2 Colour 3 Function

Yellow Yellow Yellow L/H indicator
Blue Blue Blue Fog light
White White White Earth
Green Green Green R/H indicator
Brown Brown Brown R/H tail / side light
Red Red Red Brake lights
Black Black Black L/H tail / side light
Yellow Pink Pink Reversing light
Green Orange Purple Continuous 12V supply
Blue Grey Grey Fridge
Red White/Black Clear Earth for fridge
Brown White/blue Buff Coding ( if required) normally spare
White White/Red Black/red Earth for pin 9

Most new vehicles are not to simple to wire a towbar as the wiring systems are getting more complicated and a lot require relays to by pass parts orf the car wiring

All pins no.s start from 1 at top line