Installation instructions or wiring diagram for towbar cable

[Kebnekaise]

I'm looking for the official Volvo installation instructions or wiring diagram for a towbar cable harness (7-pin Type 12N p/n 1188 229-7) for a 1991 945.
Some troglodyte used scotch lock to install the wiring directly on the tail lights in a very amateurish way and now I'm experiencing many problems when towing a trailer, from a brightly lit bulb malfunction indicator to a dimly lit instrument cluster. Errors only when trailer or bike rack is plugged in.
I'm so fed up with it and I'm planning to instal the cables as per Volvo's official instructions and go from there if there are still problems.
So is there someone out there who can help me with the instructions or diagram for a 1991 945 (not pre wired) 7-pin trailer connector Type 12N?

Oh and now we're here which relays (p/n?) do I need for the indicator light in the instrument panel and rear fog light disconnect-relay?

[Laird Scooby]

First question is have you checked, double-checked and triple-checked it doesn't already have the pre-wired towbar connectors?

Assuming you have, you need to run a length of 7-core cable from the towbar to the fusebox.

In the fusebox you'll find the BFU - Bulb Failure Unit and you'll need to connect into the feed side of that before the power goes through the unit to the lights.

Not sure which flasher relay you'll need but it needs to have an output for a warning light to power the dash mounted trailer indicator warning light.

Can't think of the answer on the rear fog cut-out just now - brain fog - but it would be a wise move to renew the existing 12N socket and also check the earths around the tail lights in the car and the earth connection in the socket. Many lighting related problems on cars with towbars tend to come from poor wiring in the socket and/or dampness, corrosion etc.

I'll try and remember about the rear fog cut out, long time since i've done one!

[Ian21401]

Some younger 900’s had a dedicated connection in the rear but my 1992 940 doesn’t have that.
I followed the instructions of gpl1968 and fitted a 7way bypass relay and a smart relay.
Have a look at the thread entitled “Towing Electrics on 1992 940 ( again, sorry )”

[Kebnekaise]

Thanks for the answers Dave and Ian.

Haven't thought of that to directly tap on the BFU, I go for that trick.
I'm aware of the earthing problems and I already have a new 12N socket. When al is in working order I will fill up the connector with silicone sealant.
The relays are just for fun but it's always nice to know how it's done.

I checked for the pre-wired towbar connector but I can't find any and will read the mentioned article.

Oh and if there's someone out there with a pdf of the official Volvo instructions, I am open to suggestions.

Niels

[Laird Scooby]

Is this the thread you mean Ian?

https://www.volvoforums.org.uk/showt...trics+1992+940

[Laird Scooby]

Originally Posted by Kebnekaise

When al is in working order I will fill up the connector with silicone sealant.

Niels

Niels - better to use silicone grease and also put some in the actual contact pins of the socket so they are also water-proofed and the plug slides in and out easier.

Silicone grease is waterproof but won't go solid like silicone sealant meaning you canremove things in future for repair/maintenance if necessary.

I've tried finding installation instructions for the electrics to no avail except for pre-wired kits and those have dedicated instructions. This pdf diagram for the 95MY 940 might be helpful, the lighting circuits didn't change much over the years so should point you in the right direction :

http://www.myvolvolibrary.info/Tech_...ction-3-39.pdf

Good luck with it!

[Ian21401]

Originally Posted by Laird Scooby

Is this the thread you mean Ian?

https://www.volvoforums.org.uk/showt...trics+1992+940

Thanks for that. There is another one somewhere by gpl1968 (he deserves all the credit ) which is where I found my info. and blatantly copied it.
I haven’t had time to try that “linky stuff” yet as I’ve been busy with those shocks and boring household stuff. (shopping, cooking and cleaning and stuff.)

Neil’s,
What Dave says about silicone grease instead of something which sets. I’ve brushed Waxoyl into mine and on the pins etc. and it has worked for me.

[Laird Scooby]

Originally Posted by Ian21401

Thanks for that. There is another one somewhere by gpl1968 (he deserves all the credit ) which is where I found my info. and blatantly copied it.
I haven’t had time to try that “linky stuff” yet as I’ve been busy with those shocks and boring household stuff. (shopping, cooking and cleaning and stuff.)

Neil’s,
What Dave says about silicone grease instead of something which sets. I’ve brushed Waxoyl into mine and on the pins etc. and it has worked for me.

Waxoyl can be more of an insulator Ian, the silicone grease is very much like dielectric grease, a good insulator and water proof but will allow current to pass happily if the contacts are good and tight enough.
Waxoyl will be fine for protecting the screw terminals in the back though and the mounting bolts.

[Ian21401]

Yes Dave, I thought that originally but I’d done the terminals etc. and just gave it a try and it seems to work. That was back in the 80’s on my Marina when we acquired our first caravan and l just continued to do it.

[Kebnekaise]

Ok guy's, after reading Dave and Ian's articles and studying the 95MY 940 (How have I missed that one?) and a good night sleep I came up with the following plan and drew attached image (click for pdf). The turn signals and rear fog light are not switched over the BFU so I think it is save to tap them directly from the tail light. Off to the shop for some length of cable, silicone grease and handful of piggy-back spade connectors.