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Scott, Master Mechanic
Category: Australia Car
Satisfied Customers: 251
Experience:  30 yrs experience with Aussie, Japanese & British cars
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X5: I Have a problem with trailer wiring. I connected a new

Customer Question

I Have a problem with trailer wiring. I connected a new caravan to my 2001 X5 4.4 ltr V8 all lights worked fine initially, 3 hrs into trip I lost all lights. Thought it might be a fuse or earth problem, these wre found to be all functioning correct. Fuses in right rear side panel checked ok. unplugged caravan and connected to another wagon (Subaru) all lights worked fine on caravan. This indicated problem is with X5 system.
Question is there a control circuit which needs to be modified or an adaptor which needs to be fitted to allow more current draw to drive more lights on caravan.
Submitted: 2 years ago.
Category: Australia Car
Expert:  Scott replied 2 years ago.
Hi there,
Sounds like you're on the right track. Indeed, it probably needs a relay in the lighting circuit. Many vehicle lighting systems are equipped with circuit breakers as opposed to fuses, allowing the light system to reset itself after the short or extra load has been removed. It's not a complex or expensive mod to fit the relay, but you will need to establish a suitable power source before the switched light circuit.
Avoiding further issues here - I would take it to an auto electrician for fit up of the relay..
I hope this helps. Feel free with any further questions here..
Customer: replied 2 years ago.
HI Scott, thanks for your prompt reply
I was looking for a more definitive BMW X5 reason, ie what module, how to bypass etc. your reply is more a generic answer with probables but no actual facts.
the symptoms of each lighting cct failing at the X5 trailer coupling ie stop light, tail/ park light and left and right turn is somewhat unusual, putting a relay in the tail light/park system has the highest current draw which would make sense but What is controlling this fuctionality in the X5 system. This must be a common issue for BMW X5's
Can you or your colleagues shed any more light (no pun intended)
Thanks TC
Expert:  Scott replied 2 years ago.
Hi again,
OK sorry I've misread the original question. Yes indeed if it's all trailer circuits it's a different issue. I thought you were talking lighting circuit, as in parking lights for whatever reason.
There's a primary control relay in there for the lighting. I've asked around & can't find anything up front other than being pointed to youtube installation tutorials for X5, which can be informative.
I may opt out now, given I can't help with specific data..