Technical Trailer stop lights

[mascot47]

Why do my trailer stop lights trip out my electrical system on my fiat ducato multijet. Can anyone help? It seems like there are too many bulbs on the circuit. It works fine when eliminating a bulb.

 

[puntodad19]

Sometimes trailer sockets and plugs can fill up with water and cause mayhem, not to mention corrosion and electrical "leakage"...

Has the system worked properly in the past, and is now playing up ?

Good tidy installation or a spaghetti special nightmare ?

 

[bugsymike]

Sometimes trailer sockets and plugs can fill up with water and cause mayhem, not to mention corrosion and electrical "leakage"...

Has the system worked properly in the past, and is now playing up ?

Good tidy installation or a spaghetti special nightmare ?

Also does the socket work with other trailers or a lighting board?
Has the van got the extra relay/circuit for the trailer for canbus systems?
I have found modern LED trailer boards are more forgiving on modern systems.

 

[Communicator]

Why do my trailer stop lights trip out my electrical system on my fiat ducato multijet. Can anyone help? It seems like there are too many bulbs on the circuit. It works fine when eliminating a bulb.

The lights are monitored by the BCM. If as suggested above by @bugsymike the is no repeat relay unit fitted, then when trailer is connected the BCM will detect excessive current and isolate the lights as deemed faulty.

 

[mascot47]

Why do my trailer stop lights trip out my electrical system on my fiat ducato multijet. Can anyone help? It seems like there are too many bulbs on the circuit. It works fine when eliminating a bulb.

 

[mascot47]

Thanks for the info. To my knowledge my vehicle has a canbus system. The lighting system on the trailer is brand new. The towbar came with plug and the wiring harness. It has been wired in to the vehicle correctly everything works except the stop lights. When I press the pedal the stop lights come on momentarily. I can hear a relay clicking on and off. I removed Obe bulb from the trailer brake lights and it all worked fine. So what do I need to add to the system and where does it go? Really appreciate any help

 

[The Panda Nut]

My experience is re check that trailer wiring first. Check the stop lights bulbs are correctly seated in the light units and eathing while you are there.. Any fault is most likely on the plug. Its so easy for this to be wrong and you cant see it for looking. Then recheck the towing relay earth to body. Brakes used to be left and right but are now a single wire for both. If the relay is clicking there is the possibility the relay has developed a fault. I find the sigle connector blocjks that come with the relays cause countless problems and dont use them. Even on can bus vehicles I would solder the relay connections. Maybe nipping the connector up with pliers might be all thats required assuming it how your is connected.

 

[Communicator]

Thanks for the info. To my knowledge my vehicle has a canbus system. The lighting system on the trailer is brand new. The towbar came with plug and the wiring harness. It has been wired in to the vehicle correctly everything works except the stop lights. When I press the pedal the stop lights come on momentarily. I can hear a relay clicking on and off. I removed Obe bulb from the trailer brake lights and it all worked fine. So what do I need to add to the system and where does it go? Really appreciate any help

Where is the supply for the trailer stop lights coming from?

 

[jackwhoo]

The towbar came with plug and the wiring harness. It has been wired in to the vehicle correctly everything works except the stop lights.

Who fitted the tow bar and wiring harness?
Was the harness a specific one that plugs into the fiat wiring harness and includes it's own bypass relay?

Did the harness come with a bypass relay ?