P2 Tow Hitch wiring harness

Post by **scot850** » 22 Jul 2023, 16:49

A buddy pulled a trailer hitch from an 06 XC70 for his car, but as he is only using it for a bicycle hitch, he did not need the harness. He gave that to me at the yard but I did not look at it. When I got it home, 2 of the wires were severed at the plug at the hitch end. One was fixable, but the other was pulled and broken at the molded plug. By chance I have a similar 4 pin plug that I have modified to use the plug cover from the original as well making a simple mod that allows the new plug to stay locked in the mount the plug sits in (the original is molded to fit into the molded bracket.

Wire colors are similar for 2/4 wires but I plan to solder the repair and heat shrink the cables so they should be inside the car.

Before I do this, while I do not use a hitch and won't on any of our AWD Volvo's (due to angle gear sympathy), does anyone use any other type of plug on their Volvo. I'm assuming as this as the Volvo harness controller unit you cannot use any other connector like the 5/7 way type some vehicles use. If this is the case I will go ahead and solder repair this cable as planned with the 4 pin cable as originally used.

I have no use for this but again hate to see something that can be repaired and someone may find a use for.

: Broken original hitch harness; PXL_20230719_214823529.jpg (302.12 KiB) Viewed 1319 times

: Replacement plug fitted; PXL_20230719_214814736.jpg (309.3 KiB) Viewed 1319 times

Even modified the original plug cover to re-use it as the replacement did not come with one.

When I disassembled the original plug holder (it is a clamshell with a hinge one end) it was full of dirt and allows dirt to fill up in there. I am thinking of filling the void with black silicon to A) further prevent the plug from possibly being pushed through the retaining clamp and B) to keep the crap out and prevent/reduce the chance of moisture entering the back of the plug. Good or bad idea?

Thanks,

Neil.

Neil.

Post by **scot850** » 23 Jul 2023, 15:38

Nobody with trailer hitch knowledge? If not, then I will just repair with the new part, bag and tag for a new owner at some point.

Decided to look up the original part. Wow, who knew there were 3 options with 4, 7 and 13 pin connectors.

The version I have is the basic one which has brake, turn and sidelight options. It does not have the rear fog-light, or back up options:

https://www.volvooftorontoparts.ca/prod ... e31ftbkgch

What I don't know is if you get all 3 in a kit or how they identify the different options. Looking further it looks like there are different plug ons that can convert to the other alternated. There is a covered over connector as part of the harness which I am presuming is the connector you can use for the 7 and 13 pin options.

Having looked at this now further, it looks like I have to repair it as original and upgrades can be bought (if available) and added on.

Neil.

Post by **scot850** » 23 Jul 2023, 19:41

The white wire is the ground. You can see it has a slight nick in the white wire sleeve near the plug. Weird thing is I have trimmed it back 2-3" from there and the wire is totally corroded!! I have traced it back up to a join maybe 18-24" in where it meet the main ground wire. I am thinking of removing the wire all the way up to there and running a new wire all the way to the plug.

Neil.

Post by **scot850** » 24 Jul 2023, 23:06

I removed about 18" of the ground wire and the wire was then 95% clean. Connected and heat shrunk all the wires and used large glue lined heat shrink tubes to overlap the cable harness. Now much better protected than originally made.

All wire buzz out nicely. The cable assembly is ready for a new home. Good thing this is the basis you need if you want 7 or 13 cable outlets which can be bought from Volvo separately and attached to the correct connector.

All is now good and I also understand how this is sold and the variants available.

Neil.

Post by **abscate** » 25 Jul 2023, 02:26

Now give me a price so I can finish my 2005 hitch install

Post by **scot850** » 25 Jul 2023, 16:06

I'll PM you on that! Does need a good home! And like I said, it can have a 7 and 13 pin adapter added if needed. I think Volvo still list them for sale. I just have to give the plug bracket a coat of paint and then it can go!

7-pin part # 30756530 - FCP shows it on back order for $100 US, Volvo of Toronto show it for sale at $100 CDN!

https://www.fcpeuro.com/products/volvo- ... o-30756530

13 pin part # 31285778 - Volvo of Toronto shows that for $150 CDN, FCP don't list this option.

Strange thing is it looks like they are added to the hitch controller replacing the whole harness and not adding onto the existing harness?

FCP shows the trailer controller as part # 30664974 - They show that for $130 US

https://www.fcpeuro.com/products/volvo- ... e-30664974

Volvo are weird.

Neil.

Post by **jonesg** » 25 Jul 2023, 20:07

I bought my trailer wiring adapter from etrailer, $70.
they all work pretty much the same, it uses optical isolating with separate power feed from battery so the trailer lights don't overload the volvo lighting system.
Optical isolation works by allowing signal to pass but no direct elec connection so voltage can't pass.

HUman neurons do the same via chemicals.

Post by **br0dy519** » 26 Jul 2023, 11:43

I bought mine from u-haul for $15. Spliced into the harness in the spare wheel well.

viewtopic.php?p=596390#p596390

Post by **scot850** » 26 Jul 2023, 19:10

I prefer not to muck around with factory wiring if possible. Way too many wiring issues over the years with poorly executed add-ons. When I was working at the Volvo dealer in parts for a while, it was surprising how many of the mechanics said they had had to repair harnesses and other electrical damage from poor wiring additions.

I was looking at adding a remote start to my wife's car of the time (now our son's) 06 XC70. I was warned in no uncertain terms not to use any aftermarket units due to the damage that some cars had received from doing this. This was not a fright tactic, and it was from a 40 year veteran Volvo shop foreman.

I have added a Viper remote start and immobilizer to mu 00 V70R, but the car had come with no remotes and already had a remote start that then failed. So far, 10 years later it is still ok, but the P80 is less complex the the P2.

Would I spend the money to buy a Volvo harness, probably not, but then I have no intention of fitting a hitch! If someone like Abscate wants this and is happy to have the item for a fraction of the original cost, then I am happy to help! Hate to see good parts crushed!

Neil.