New XC60 with Volvo towbar - no Fridge connection

[Yet another Mike]

We have had our MY2017 XC60 just over a week. We had the detatchable towbar fitted as a factory option. I just got round to checking the towbar and electrics with our caravan.

As a minor point the towbar comes with the ball painted black - not good for a modern tow-hitch with stabiliser pads. The paint would contaminate them very quickly. That was easy to sort with about 15 minutes work with wet and dry abrasive.

Then the electrics. The road lights are all correct. The permanent 12V feed on pin 9 is fine, as are the earth connections on pins 11 and 13. BUT, there is no 12V supply for the fridge on pin 10 when the engine is running.

I wasn't surprised because I had exactly the same problem about 10 years ago when we bought our previous XC90; and a friend who has a Honda CR-V had the same problem when it was bought new last year.

It does seem to be a regular problem with modern cars. I suspect there are many people driving around towing their caravans assuming the fridge is being powered as they drive along and it isn't. Not much of a problem for a few hours drive in this country, but potentially a big problem if you are undertaking long distance drives in the Summer on the Continent.

Anyway I shall present the problem to our dealer on Monday and no doubt it will be sorted in due course, hopefully using the full 2.5mm thick cable called for by the standard specification.

Posted as a warning to other people with new towbars fitted - if you care about your caravan fridge being powered as you travel, do check (or have checked) the 12 Volt supply on pin 10 and associated earth on pin 11.

[Billggski]

This is a regular issue, the cabling needs to be stronger than usual because of the length of the connection, and the fridge can flatten the battery, so special set up is required.
The caravan and motorhome club say....
A common concern of owners is the precise point at which the ignition-controlled circuit goes live. At one time, access to an appropriate connection on the vehicle alternator made it straightforward to ensure this point was only once the engine was actually running, and not just when the ignition was turned to on. Modern engine bay and alternator designs limit such access considerably, often making a direct connection to the alternator impractical. Some wiring kits just use a connection to an ‘ignition-on only’ power supply. These successfully prevent the fridge flattening the car battery while parked, but do not protect against the situation where the car battery is already flat and the engine attempts to start from the caravan one. However, the Club has no reports from members of such problems occurring in practice. Wiring kits using a voltage sensing switch (sometimes called a ‘smart’ relay) address this issue (if correctly set up), as their sensitivity means they can detect the difference between the nominally 12V supply from the car battery (usually ~12.5V), and the nominally 12V output of the alternator (usually ~14V). Such systems only switch the caravan battery into circuit once the alternator is outputting power – ie the engine is turning.

[Ian21401]

I may be missing something here as I am old school so far as vehicle electrics are concerned.
Back in the 70's I wired my old Marina with a twin output relay mounted in the engine compartment with main feed direct from the alternator and a dash mounted switch to control the relay.
I wired my 940 in 2012 with a smart relay for the battery and fridge via the 12S socket. The feed to the smart relay is via large gauge (40amp) wiring (with a 17amp line fuse) direct from the battery +ve. and 17amp wiring from the relay to earth. This seems to work well.
I'm particularly interested in this subject as my daughter has recently acquired a 2011 XC70 and is currently investigating tow hitch suppliers and fitters. The local main Volvo dealer is quoting just short of £800 against various other sources (e.g.Witter) at £479. She had a Witter hitch with twin 12N & 12S sockets fitted by a local Witter approved fitter to her previous V50 but the battery and fridge supplies from the !2S failed shortly before she sold the car on.
I understand that the smart relay monitors the voltage it is receiving and switches in when the engine is running but where is it receiving this 13.0+ volts from and through what wiring?

[Whyman]

Thanks for the post, as a result of this I have checked my XC60 and guess what no supply for the fridge.

Towbar and electrics were fitted over 3 years ago when I bought the car and probably never worked from day one. Checked with a multimeter and no output even with the engine running even after about 10 minutes. I would have expected a voltage sensitive relay to have clicked over, by then, if it was going to.

There is a grey wire going to pin 10 in the 13 pin socket but I have not checked if it is connected to anything. The Volvo electrics installation guide says there is a supply for the fridge and the only fuse fitted in position 4 is OK and pin 9 is a permanent Live.

Any ideas on what I should be looking for?

If I find nothing does anyone have a recommendation on a voltage sensitive relay?

[Clan]

Originally Posted by Whyman

Thanks for the post, as a result of this I have checked my XC60 and guess what no supply for the fridge.

Towbar and electrics were fitted over 3 years ago when I bought the car and probably never worked from day one. Checked with a multimeter and no output even with the engine running even after about 10 minutes. I would have expected a voltage sensitive relay to have clicked over, by then, if it was going to.

There is a grey wire going to pin 10 in the 13 pin socket but I have not checked if it is connected to anything. The Volvo electrics installation guide says there is a supply for the fridge and the only fuse fitted in position 4 is OK and pin 9 is a permanent Live.

Any ideas on what I should be looking for?

If I find nothing does anyone have a recommendation on a voltage sensitive relay?

Volvo have never wired the Fridge connection historically for what ever reason . With the models from 2005 with trailer module it is all controlled by the software in the trailer module as to which pin does what from information going around the main network system .. It doesn't mention the word fridge anywhere in the installation instructions . Pin 10 is labelled as 12v with ign on however .. This could be country related .If you want a fridge feed you could use a voltage operated relay but be careful of overloading the main Trailer module Thick Red input wire ( How much current does a Caravan Fridge draw ? ) You would also need a genuine direct ignition supply as a signal to work the relay , not that easy to find on modern cars !

[Yet another Mike]

Good news (as far as I am concerned). Spoke with the dealers today and they promised to ring me back. They rang back within 5 minutes armed with their senior technician. Apparently this is a commonly reported spurious fault.

These things are more intelligent than I am. The "system" looks for a fridge to be connected and if it detects one it will provide the 12 volts. If not - and a multimeter will not do the job - it does not provide the power!

The only way to check is to plug your caravan in, run the engine and see if the fridge shows any signs of having power (which would depend upon the model).

Sorry to spread alarm unduly.

Mike

[pagan8c]

I spoke to Volvo Customer services today and was sent a message back sying that the Towbar 13 pin connection will power the fridge . I have the factory fit semi electric towbar on my XC90 but as I only got it on Friday have not connected it or towed my caravan yet. I am waiting to get a few miles on before putting the van on the back.

[Whyman]

Thanks for the update guys. I was sort of coming to think that this may be the case as the wiring instructions clearly shows pin 10'as being an ignition controlled 12v supply for the fridge

I will connect then van tomorrow and see if the fridge bursts into life. Will report back tomorrow.

[Whyman]

Plugged the van in today.

With it switched to battery but engine not running there was an alarm sound, the battery symbol on the fridge flashed and there was also and triangular warning symbol flashing red. As soon as I started the car all was well.

The battery symbol was steady, no warning sound and the flashing warning symbol had gone out clearly showing that there was 12v power to the fridge once the engine was running. I did not keep it running long enough to feel the fridge get cold.

[Ian21401]

So Yet another Mike has established that the Volvo clever electronics detect the fridge connection and deliver power accordingly. I presume that this is the "trailer module" which is acting as a "very" smart relay.
Does it also detect that there is a battery fitted in the caravan and send a charging current to it?
I'm led to believe that the is a "trailer plug" somewhere in the rear of the car. Is this the "trailer module" or is it what the trailer module must be connected to?
If the trailer module is not already in situ and is installed as part of the hitch fitting, are independent fitters able to source said module as a "Bosch" or similar part or is it only available from Volvo at some inflated price?

Thanks for your update Whyman. Re your comment about not waiting to feel the fridge get cold. My understanding is that when running on 12volt the fridge will only maintain whatever temperature it was at when the 12v was switched on which is why it is advisable to run the fridge on gas or 240v long enough to cool it to the desired temperature prior to towing.