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Discussion Starter · #1 ·
Hi,
Had to tow this beast of a trailer yesterday (see pic below).

I only realized late in the game that I had this crazy “euro” 7-pin wiring harness that was not compatible with any adapters at any stores anywhere!!!

I called the dealer on the off-chance that they might have something in stock. The bit I needed was $200 so I was kind of happy no one did have it in stock. The bad news is that I was still stuck towing using hand signals! So here I am at the sailing regatta 3hrs from home and I still need to tow these damned things back. Just wondering if there is an easy way to cut into wiring to install a “normal” flat 4-pin harness.

Has anyone come across this? VIDA would probably help to confirm which wire is which but of course I don’t have that on hand either. Guy at dealership couldn’t understand why an adapter would cost so much and he was concerned that there might be fancy electronics involved to covert the signals. I’m not convinced.




2002 V70XC, 2003 V40, 2004 S60, 2010 V70
 

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So the car has 7 pin and the trailer has 4 pin?
 

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Discussion Starter · #3 ·
Correct But it’s not your typical spade type seven pin connecter it’s a combination of male and female connectors.


2002 V70XC, 2003 V40, 2004 S60, 2010 V70
 

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Discussion Starter · #4 ·
Alright, I think I’ve got it straightened out. I purchased a kit called “4-way tail light converter” from princess auto part #8465841 and traced all the 7-pin connectors and spliced to the adapter. If anyone else encounters this here was the wiring breakdown for my 02 V70XC:


Male harness connectors:
Black ground
Green left turn
Green white right turn
Grey 12v switched parking light
White 12v switched
Yellow - brake light




2002 V70XC, 2003 V40, 2004 S60, 2010 V70
 

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This is the diagram for 2002 V70.

The white is a parking light feed along with the gray.
They are split left and right hand side.

The switched 12v positive is blue on pin 1.
You may need to fit a fuse in position 15 in the rear fuse box.
 

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I haven't had a car or truck in the last 30 years that hasn't run the 7 pin connector as pictured, then again all my trailers have amber direction indicators / turn signal lights and dedicated brake lights!
 

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Discussion Starter · #7 ·
I haven't had a car or truck in the last 30 years that hasn't run the 7 pin connector as pictured, then again all my trailers have amber direction indicators / turn signal lights and dedicated brake lights!
Interesting - are you sure yours weren’t 7 pin flat connector? I did some more research and the seven pin on mine is a euro standard called “multicon west”. Not common at all in NA.


2002 V70XC, 2003 V40, 2004 S60, 2010 V70
 

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Interesting thread, I have only had my 2007 XC70 a few months and one thing I want to add to it is a hitch and wiring to pull a small trailer with motorcycle or sail boat.
Maybe the real "odd" item around the world may be the US / Canada flat 4 wiring for only the most basic running lights, brake lights, and turn signals?
I know that on my other trucks that use a brake controller also have 7 connections, including 12v running to the plug / trailer to work with electric brakes.
I wonder if the 7 pin as shown is the ROW (rest of world) standard wiring and also incorporates trailer brakes??
Does the dealer have the mating trailer side plug available and from there you could tie into the 3 wires needed (+ ground) for the flat 4? Or possibly source from the internet if common for the ROW. I need to dig into the trailer hitch project, and from what I understand the dealer does have a harness that plugs into the car harness with no splicing to give you the plug for the trailer, I now wonder what is supplied?
If anyone has added the hitch and dealer wiring option please chime in or send me a PM.

Best Regards
 

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Down under in Australia, most states now have a rule about using a 7 pin connector, there is 3 automotive types and another type only used on semi tractors. There is the one you pictured, the 7 pin continental type, a flat type, which can also come in 12 pin configuration normally used when your camper requires accessory powers etc and there is a small utilux 7 pin connector. I use the same one as you showed, pins 1-7 left turn, reverse, ground, right turn, electric brakes, stop, brake, the use of pin 2&5 are pretty much optional, many using pin 2 as a power pass through. The advantage of the 7 over the 4, is that when you turn, and brake both brake lights are on solid.
 

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This is a wiring diagram to convert 7 to 4 pin assuming that the trailer brake lights are the turn signals.
 

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Discussion Starter · #11 ·
Interesting thread, I have only had my 2007 XC70 a few months and one thing I want to add to it is a hitch and wiring to pull a small trailer with motorcycle or sail boat.
Maybe the real "odd" item around the world may be the US / Canada flat 4 wiring for only the most basic running lights, brake lights, and turn signals?
I know that on my other trucks that use a brake controller also have 7 connections, including 12v running to the plug / trailer to work with electric brakes.
I wonder if the 7 pin as shown is the ROW (rest of world) standard wiring and also incorporates trailer brakes??
Does the dealer have the mating trailer side plug available and from there you could tie into the 3 wires needed (+ ground) for the flat 4? Or possibly source from the internet if common for the ROW. I need to dig into the trailer hitch project, and from what I understand the dealer does have a harness that plugs into the car harness with no splicing to give you the plug for the trailer, I now wonder what is supplied?
If anyone has added the hitch and dealer wiring option please chime in or send me a PM.

Best Regards
I think you are right in that 4 pin flat is an NA thing for utility trailers, small boat trailers, small storage trailers, etc. Any larger trailer uses 7 pin but NOT the 7 pin type that was found on the back of my volvo. Even the dealership said, yeah not sure why volvo chose that connector for earlier P2’s. It didn’t make any sense. Thanks to all for the info. In the end I disconnected the 7 pin altogether and wired in a 4 pin flat type. Honestly with the very, very modest tow limit of 1100 lb, I won’t be towing anything requiring any thing more sophisticated. It has got me thinking about a transmission cooler though...


2002 V70XC, 2003 V40, 2004 S60, 2010 V70
 

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As in the picture of the 7 pin on the XC70, what is the numbering sequence? We have 4 f.male 3 male plugs. I saw Rogers copy of the factory layout which is pretty clear but the side bar go to 12 although the wiring is pretty clear. I assume the plug its self is numbered.

Thanks for posting!
 

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Discussion Starter · #13 ·
As in the picture of the 7 pin on the XC70, what is the numbering sequence? We have 4 f.male 3 male plugs. I saw Rogers copy of the factory layout which is pretty clear but the side bar go to 12 although the wiring is pretty clear. I assume the plug its self is numbered.

Thanks for posting!
Pretty sure it’s the first diagram in figure below. Just search for “7 pin multicon”




2002 V70XC, 2003 V40, 2004 S60, 2010 V70
 

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That diagram is different to what we have on the same 7 pin plug as used here in Australia for over 50 years, ours are
Pin 1 yellow, left turn
Pin 2 black, reverse lights or +ve pass through
Pin 3 white, ground
Pin 4 green, right turn
Pin 5 blue, electric trailer brake control
Pin 6 red, brake lights
Pin 7 brown, tail lights

These are the standard colors on any
trailer, here, unfortunately, vehicle manufacturers don't normally stick to the code colors unless they have a pre made trailer socket harness that is sold as an accessory.
 

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As in the picture of the 7 pin on the XC70, what is the numbering sequence? We have 4 f.male 3 male plugs. I saw Rogers copy of the factory layout which is pretty clear but the side bar go to 12 although the wiring is pretty clear. I assume the plug its self is numbered.

Thanks for posting!
Yes the numbers are for the pins in the plug in the boot.
Volvo do or did do, several different harnesses that had different sockets at the tow bar end that went back to the plug in the boot.
 
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