My 2017 has a retrofitted towbar that appears to be coded correctly. Fogs are disabled when the trailer is attached, parking sensors off etc, bulb warnings work......

 

Problem is I've noticed that sometimes the cruise control works when towing and sometimes not. It always works fine with no trailer electrics fitted.

 

Now..sometimes when towing I get a bulb out warning for a few seconds even though everythig is working when I leave home and also when I get to my destination, its a boat trailer with removeable trailer board and the lighting board gets shaken up pretty violently over bumps which I think is the cause of this. I now think that once there is a bulb out warning the cruise is disabled until the car is restarted. Has anyone else observed this behavior?

 

If this is the case I'll look at getting a newer trailer board using LEDs but then I also wonder if this will cause the car to go haywire due to the low current draw.

Hi,

Before buying a new lighting board, I would start checking the current one.

May be there’s a weak cable somewhere making a false contact or a shortcut. I would also check the plugs of the trailer which could be partially rusted, leadind to the same symptoms as above. I think this may be a common issue on boat trailers since operated in moist / salt conditions.

I assume there are 2 plugs on your boat trailer (1 for the hook / 1 for the lighting board)

 

These could be the root causes of all what you’re facing.

Ive totally rebuilt the lighting board before but it still gives the same problems almost straight away. I even replaced the plastic plugs with metal as these don't wear in the same way. They just get battered being taken off and back on every outing and the mounting poles way out past the back of the boat mean there is loads of vibration. My feeling of moving to LED avoids much of these problems as they will be more vibration resistant but its likely the CANBUS wouldn't like them due to the low currents drawn. 

 

I guess my main question is if anyone has had their cruise control disabled by a bulb out on the trailer?

Hi

I can't comment about cruise control when towing, as I never use it. However, when towing our caravan with my 2016 Estate, I do periodically get a bulb out warning for an indicator, even though all is working normally (checked as soon as possible after the warning).

Cheers

Paul R T

Sometimes the trailer raises a warning because its both rear lights are connected to the same pin of the tow bar plug. Then, as the bulb failure detection system sees no current on one of the two rear light pins, it triggers a warning.

May be worth to check.

It's in the manual, cruise control is disabled if the car believes any of the lights (bulbs) to be inoperative.

 

Your occasional blown bulb warning is the clue here, there's a fault somewhere in the wiring.