I tow my 2019 Troll 540 with either a 2016 435d BMW or with a 2020 V60. The BMW is fitted incandescent bulbs, the V60 has LEDs.

Last year I did 1,500 miles in the BMW across Europe and back without any issues. Last week I went on a round-trip of 250 miles and started getting multiple intermittent bulb failure messages for each of the "trailer lights" on the van. The messages came and went, apparently at random. I have never seen the issue with the V60; neither last year nor this year.

So I stopped the car to check and found that some of the van lights were actually not working. I then switched-off the ignition, disconnected and reconnected the electrical connection between the car and the van and found the lights worked without issue for a short while (10 mins) before the random bulb-failure messages started appearing again, albeit with a lower frequency.

Since getting home I have thoroughly cleaned the car's connector socket and carried out lighting tests on the driveway. All worked and no alarms have appeared...yet!

I have read that cars using the CANBUS system for management and which are equipped with incandescent bulbs (like the BMW) can throw out bulb failure alarms if connected to a trailer/van with LED bulbs. This is reportedly because when the CANBUS system performs a routine bulb check, it is looking for an incandescent bulb electrical load which is significantly higher than the load generated by an LED bulb. Hence the system thinks it has a failed bulb when it tests an LED circuit..

I know that it is possible to buy adapters to address the issue but they are costly and some of the feedback suggests that they often don't work. (Carpoint 0440140 Canbus LED Adaptor 13-Pin on Amazon £58)

My reason for posting is to ask:
1) Has anyone else seen the bulb failure messages issue and resolved it - especially if towing with a BMW?
2) Can anyone suggest a reason why the bulb failure messages have only just started appearing? (this is the 3rd year of towing with the BMW)
3) Has anyone ever bought one of the LED trailer light adapters and did it work?

Cheers

could put led bulbs in eriba, although would still spark the warning

under the floor, the older eribas there is a box with wires for lights in, check to see if connections gone green causing a higher resistance, clean there is a spray minds gone blank on name.

my lower front lights the connections needed cleaning behind the capless 501 bulbs.

the car brain remembers faults see if can get them cleared,

Belated closure of this issue. I disassemble and reassembled the plug on the van and the socket on the BMW (not for the first time) and problem solved! Phew!

It's funny how these apparently random problems come up. My Volvo V40 has all LED lights at the rear, except for the brake light and reversing light bulbs. When I had the towing module "activated" by Volvo back in March, it seemed to upset something in the Canbus - as a result, every day or so, the car would blow the right hand rear brake light bulb. I have solved that issue by putting in an LED brake light bulb. Just that one bulb. Now it doesn't blow any more.... If I put an LED bulb in the left hand side it then stops the radio working every time you brake... At the moment all is OK, so I'm leaving it as is...

Not sure if it's relevant, but when I had a Touareg, I had all sorts of intermittent issues which were finally resolved when the dealer found that the towing electrics had been set in the vehicle's firmware to US rather than UK - all went away when it was set correctly.

Never got an answer as to why it should make a difference.

Might be worth getting whoever services your BMW to plug their diagnostic kit in and looking at the towing configuration which could have been reset during a service.

John

Honda CV cut out with blown fuse every time reverse was actioned, fault was due to led bulbs fitted in reversing lights?

Not as interesting as above problems but on our recent tour to Scotland the bulb fail light lit up on our Kodiaq towing our 540. it turned out to be the passenger side indicator. As I am really organised I carry a spare but as I have a failing memory I couldn't remember the safe place I had put it in................!

Hence a visit to Halfords in Inverness and the purchase of two new bulbs. Got under the van and fitted it - quick check and everything was working again. However on journey down to Pitlochry the warning light came on again. Same process again put the other spare in and everything was working fine. Drove down to Strathclyde Country Park & double checked everything was still working. Got to Gretna Green Service area next day & everything OK. However drove out onto the Southbound roundabout where there was a massive pothole that I couldn't avoid and straight away the warning light was on again.

It appears clear now that the terrible state of our roads with potholes was the cause of the problem - the thumps were knocking the bulb slightly out of the fitting and hence the warning light.

When I got home again I got under the Troll and reconnected the bulb and hey presto, back on it came. The van had to go in to our service engineer for something else so I asked him to have a look and everything was working OK.

I wonder what the response of the police might have been if they had pulled me over for no indicator working as I turned left...............?

Our good old roads yet again...........

MikeT