Towbar Electrics

[Simon5030]

So, i fitted my towbar some time ago and decided to purchase a genuine wiring loom from Mr T.!
Wired it all in, tested it with a meter and all seemed to be functioning, its only when i came to tow that things started to look at bit sketchy!

Borrowed a special lead to test the socket with that puts the correct load on the electrics, everything worked except hazards and indicators, when you put the hazards on the test lead shows them both flashing but the brightness was at 50%, with the left indicator on the lead showed that that the left indicator came on at full power but also the right at 50%, exactly the same for right indicator.

Checked all the wiring several times, all the sockets are completely idiot proof, got someone else to check the socket wiring just in case i was cracking up

The only thing i was unsure about was in the manual there was a reference to what looked like an alternative configuration, i am assuming this related to a variant on the wiring?


I tried the various permutations but none seemed to help the problem relating to the indicators even though the picture is suggesting check hazards!
Checked all earthing points and continuity and everything was ok?????

The next thing i looked at was the little red box thing!

Assuming this allows the CANbus to communicate with the towing loom and lights? but beyond that i dont know

Any suggestions on this one?

Simon

 

[Towpack]

As your car uses Canbus there should be a Canbus bypass relay for the towing electrics. The relay in the pic could be it although there doesn't seem to be enough wires from it compared to others I've seen, typical 7 inputs and 7 outputs. AFAIK It just converts the Canbus signals from the cars loom to direct DC outputs to the trailer/caravan wiring which will be wired conventionally. If all the wiring connections check out OK it could be a faulty relay. You could try reversing the L+R indicator inputs to the relay and see if it moves the fault to the other side. If it doesn't than it must be the relay. JMO

 

[Rob Cowell]

Did the little red box come with your towbar electrics? This is interesting because I also have a 2005 120 (LC3) and I just spliced my cheapy, generic "loom" into the cables feeding the back lights. I was a bit unsure as to whether I should have used a Canbus relay. Worked fine for 3 years now and I tow a lot. No cables melted yet! Only 7 pin electrics. Are you on 13 pin?

 

[Simon5030]

Rob
Yes it comes with the full kit so it must be the right one!
I was going to splice originally but i dont like the little blue splicing connectors as they have been know to give me problems if they get a bit damp!
I find it strange that its only a problem on the indicators/hazards and the booklet keeps prompting you to check the hazards!

Simon

 

[Simon5030]

Towpack

Sorry i may have misled you, the problem is the same but just reversed on each indicator, ie left shows working and right on half light, right working and left on half light

 

[Towpack]

I don't have a Canbus controlled vehicle but, from what experience I've had with it on a friends car, there's no way just splicing in the tow bar wiring without a module as Rob has done would work correctly. On many modern vehicles the correct module is required and some recoding may be required. Are the lights on the 120 definitely Canbus controlled?

 

[Airhoguk]

Hi, 120 isn't CANBUS, just old school electrics. Has it actually been tested on a proper lighting board or caravan/trailer as the testers aren't particularly good and cause issues due to them being fitted with LED's and not appropriate wattage bulbs. Well documented when introduced as part of the MOT. Regarding the connection being removed from the installation manual this is only if you have fitted the bulb failure module referenced by the seperate part number so you need to leave the shorting block in if this module isn't fitted. Hope this helps.

 

[Simon5030]

Hi, 120 isn't CANBUS, just old school electrics. Has it actually been tested on a proper lighting board or caravan/trailer as the testers aren't particularly good and cause issues due to them being fitted with LED's and not appropriate wattage bulbs. Well documented when introduced as part of the MOT. Regarding the connection being removed from the installation manual this is only if you have fitted the bulb failure module referenced by the seperate part number so you need to leave the shorting block in if this module isn't fitted. Hope this helps.

Thats odd, my 2005 has got a hybrid ODB1, seems like a transitional system to ODB2. Fully agree with the trailer board thing V tester, i found the problem when i hooked up a trailer but thinking about it the tester did give a different result!
i think i will go back to a trailer board ( without LED bulbs!)

thanks