TOW BAR ELECTRICS

I was very interested in the report of Mr LeWorthy's about "That wonderful thirteen pin plug?", especially as I was about to take delivery of a new XC70 and already entertained serious doubts about the height of the tow ball (and had pestered the Sales Manager and the Service Manager accordingly) because of the XC70's higher than usual ground clearance.

I therefore printed Dennis LeWorthy's and Brian Ingle's comments, and took them to show to the dealer. Apparently this is how they do it anyway, including connecting pin 11 to earth, and the checks that I have made since taking delivery all prove to be OK.

One thing did puzzle me about Dennis LeWorthy's report. Having gone to so much trouble checking the plugs and tracing connections, why not go the whole hog? Remove the 7N and 7S plugs and use the 13 pin plug from the adaptor instead. After all, that's how the adaptor is supplied, with 2 sets of wires into one plug. Doing so would not only make for easier and more certain connection using only the 13 pin plug into the 13 pin socket (it doesn't get waggled about when being connected and disconnected, and has a surer grip) but also eliminate the problems of what to do with the excess wire and where to put the 12N and 12S plug and socket connections when towing. It would also remove a certain amount of unnecessary wiring, the presence of which serves only to increase electrical resistance.

Am I missing something? I know it looks a bit tricky to wire the plug with so many connections in such a small space, but someone managed it when the adaptor was wired and I expect the rest of us could do it if we tried.

I intend to re-plug my own caravan in this way, unless someone points out a problem that I have overlooked. I shall keep an eye on this forum for a while!

What do you think, Mr LeWorthy? Am I heading for trouble?

Michael Blyton

[Bob]

Dennis is away for a few days but I will ask him to look at your post when he gets back.

There should be no problem in fitting a 13 pin plug to your caravan cabling. You can buy these plugs from most caravan dealers for around £10 rather than using the plug from the adaptor lead supplied (just in case you need to tow something else).

I intend to do this myself eventually, but have not yet got round to it. In the meantime, I have been using the adaptor lead without any problems. You just have to be carefull and wrap the excess cable around the jockey wheel to prevent it dragging on the ground. If you do use the Volvo adaptor lead remember to change two of the wires as shown in my previous comment (and Dennis LeWorthys comments) unless you are lucky and it comes wired correct.

Remember these comments only apply to post 1998 caravans although there are some models that were changed earlier than that.

It would be interesting to know if your garage is connecting pin 11 to earth off their own bat, or following a Volvo instruction. The Volvo wiring diagram showed to me by my garage clearly said "pin 11 not connected"

On a separate note, the D5 engine has performed very well on towing.

Brian Ingle