XC70 -Intermittent Trailer Indicator Fault

[The Stimulator]

New to this towing game, but with a 2015 XC70 D5 AWD thought we’d give it a go. The vehicle is fitted with a dealer fit Volvo tow bar, and electrics. Our caravan has LED rear light clusters.

For the first 500 miles or so all was fine, but we have now started getting intermittent Right Trailer Indicator Fault messages and the indicators flash on that side at double speed. Checking the indicators, every bulb is working in the LED array, as are all the car indicators.

I have tried cleaning the car and caravan 13 pin connector, but this fault returns. If the car had a wiring adaptor that wasn’t designed for LED bulbs I would expect this fault indication to be present all the time. Is that a false assumption on my part?

[Ian21401]

On some of my previous cars the indicators flashed at double speed when a bulb on that side had failed. On later cars, and I think on my current Volvo, when an indicator bulb failed the remaining bulbs did not flash but stayed on as a steady light.
Are all the lights working when you have the message displayed and they are at double speed?
Are there any “repeater” lights on the side of the caravan which you may not have noticed and which may have an intermittent fault?
Or there is a poor connection or earth somewhere in the caravan’s right hand indicator wiring.

[The Stimulator]

Hi Ian,

Thanks for the reply.

All the right side indicators flash at double speed, although all are working. Not seen a repeater indicator on the side of the van but will have another check.

Crawling under the van, the connections all look well sealed, not sure I have the confidence to go removing the sealant, so it may be a caravan mechanics job 🙂. Certainly to get to the actual light bar at the back needs more bodywork removing than I really want to do.

Iain

[Ian21401]

By “all the right side indicators” I presume that includes the car’s indicators.
Was the car fitted with the dealer fitted towing electrics in your ownership or by a previous owner and is it possible that there is an intermittent fault with the trailer wiring that is inside the car.?
Are the caravan LED rear lights original fitment or an after market add on?

[The Stimulator]

Originally Posted by Ian21401

By “all the right side indicators” I presume that includes the car’s indicators.
Was the car fitted with the dealer fitted towing electrics in your ownership or by a previous owner and is it possible that there is an intermittent fault with the trailer wiring that is inside the car.?
Are the caravan LED rear lights original fitment or an after market add on?

Morning Ian,

Yes, it’s the car indicators as well, they are all working.

The dealer fit Volvo tow bar/loom was fitted before I got the car. I did have a look at the wiring yesterday, and again it is so well sealed I’m loathe to unwrap it at the moment, but will look to get it checked when the car is in for a service.

The caravan, a 2021 Adria Adora comes with full LED lights as standard, and hidden screws to get access to them. The lights all work.

I suspect much of this is going to need checking by someone with skills beyond mine (basically finding connections on the loom and spraying with WD40 Electrical Connection Cleaner)

Thanks again for replying

Iain

[apersson850]

In a 2015, the TRailer Module is prepared for LED on the trailer from the beginning. That was introduced in 2013.

Turn indicator monitoring starts as soon as you connect the trailer. That's sensed by seeing that the rear lights draw some current.
The TRM will then start probing the turn indicators and the brake light on the trailer, even when it's not in use. If a fault (no connection) is found, a message will show up. If you then use the turn indicators, they'll flash faster.

In your case the TRM senses an impedance too high for it to believe that the turn indicators work properly. Obviously they do. Most common problem is the connection between socket and plug. Second inside the plug. Less common somewhere in internal connections on the trailer.
If it's possible to reach the wiring to the turn indicator somewhere, like in a connection box, you can try connecting an extra bulb there, in parallel. If it works, and the error goes away, you know the connection is good up to that lamp. Can help isolating where the issue is located.

[Clan]

Originally Posted by The Stimulator

New to this towing game, but with a 2015 XC70 D5 AWD thought we’d give it a go. The vehicle is fitted with a dealer fit Volvo tow bar, and electrics. Our caravan has LED rear light clusters.

For the first 500 miles or so all was fine, but we have now started getting intermittent Right Trailer Indicator Fault messages and the indicators flash on that side at double speed. Checking the indicators, every bulb is working in the LED array, as are all the car indicators.

I have tried cleaning the car and caravan 13 pin connector, but this fault returns. If the car had a wiring adaptor that wasn’t designed for LED bulbs I would expect this fault indication to be present all the time. Is that a false assumption on my part?

As it was working ok at first I would think the problem is with the caravan .. LED lights on cars which are poor quality , that is those that did not come with the car from the factory are very poor and often have a short life , You cant beat bulbs .

[apersson850]

LEDs beat bulbs every day in the week, but that doesn't matter here. It's not a fault on the car he's looking for.

[Snackbar]

Did you manage to get this resolved…I’ve also encountered exactly the same issue and am aware of a couple of others who have the same issue.
When checking the electrics on the socket it would appear that the Pin for the fridge earth has been getting hot as the socket on the car around that Pin ha started to melt.

[apersson850]

If connected correctly to a 13-pin socket, the 12 V supply to the fridge should not use the same earth as the indicator lights.