850 Tow electrics problem

[Brucie24]

Hello all,

I have just replaced the N socket in readiness for holiday but have found that the right side light is inop. I have checked the socket connections and all is in order however have found no power is reaching the pin 5 (brown).

Now my problem is on lifting the carpet etc have found a mass of cable and scotch blocks. Have checked for voltage at scotch block fitted to brown cable and nothing there.

As I don't know if this ever worked I now need to know exactly which cable should be spliced into. At the moment it is a violet/white going to rear right cluster but no voltage is present.

Any ideas would be very gratefully received as we are supposed to leave in the very early hours of Saturday morning.

Thanks

[Clan]

from memory , violet/white is rear fog light try turning that on and see if the tail light works , if so its been wrongly connected of course ...

[Brucie24]

Originally Posted by Clan

from memory , violet/white is rear fog light try turning that on and see if the tail light works , if so its been wrongly connected of course ...

Tow fog light wire (blue) is connected to a violet/white cable which goes to lower left light cluster. Fog light on the light board works so assume that is connected correctly. Just went out to double check.....fog light on board works but vehicle ones don't

Am starting to panic now

[Clan]

The Trailer lights are going direct to the car lights ? Oh dear , they must go to the FRONT or input side of the bulb fail unit which is tucked under the chassis rail ledge on the left side . The extra load could have damaged the rear bulb fail unit ... But the car tail light is still working? probe the violet / white wire see if it is live ... it must be if the right tail light is working and thats the correct wire .
You say the brown wire AND the blue wire connect to a Violet/white? all very confusing ....
scotch locks are rubbish so ditch them and solder all the connections

[Brucie24]

Originally Posted by Clan

The Trailer lights are going direct to the car lights ? Oh dear , they must go to the FRONT or input side of the bulb fail unit which is tucked under the chassis rail ledge on the left side . The extra load could have damaged the rear bulb fail unit ... But the car tail light is still working? probe the violet / white wire see if it is live ... it must be if the right tail light is working and thats the correct wire .
You say the brown wire AND the blue wire connect to a Violet/white? all very confusing ....
scotch locks are rubbish so ditch them and solder all the connections

Okay we progress....

To answer above first, yes all four tail lights (2 ea side lower cluster) are working. LH tow tail light also working. All the scotch locks are left hand side by rear bulb fail unit and yes replacing them all will be first job tomorrow morning I hate them and never use them! Indicators and brake lights also working fine on both vehicle and tow.

You got me thinking about v/w wire, there are two connected to left cluster and one on right cluster, neither car fogs working but tow fog does. So... disconnected right v/w from brown and added to blue already connected with v/w from lhs cluster. This resulted in RH car fog working and tow fog working, a step forward but does not explain why LH car fog still not working (have checked lamp). I can live with this set up for now and worry about the LH fog on return from hols.

That leaves the question as to where to splice in the RH tow side light (Brown wire). I suspect if I link it to the spot where LH (Black wire) is connected (white/grey wire coming from term 6 of rear light control unit) power consuption would be too high.

Any ideas?

Thank you very much for your input so far it really is appreciated.

[Clan]

I thought V/W was fog light
it comes up from switch at the front , goes to left rear fog light , then loops over to the right fog light , hence two wires at the left light and one at the right .. also hence why the left fog light doesnt work , it's not meant to t here is usualy a blank in there to stop you fitting a bulb .. the 12N socket should have a fog light cut out switch in it if it's to volvo specification to turn the car fog lamps out when you have the caravan on the back ...

so all you need now is to find the right tail light feed which comes from the front and goes into the INPUT side of the bulb fail unit and connect brown wire to this ... if you connect the brown wire to left tail light wire it's going to overload the bulb fail unit ...

[Brucie24]

Originally Posted by Clan

I thought V/W was fog light
it comes up from switch at the front , goes to left rear fog light , then loops over to the right fog light , hence two wires at the left light and one at the right .. also hence why the left fog light doesnt work , it's not meant to t here is usualy a blank in there to stop you fitting a bulb .. the 12N socket should have a fog light cut out switch in it if it's to volvo specification to turn the car fog lamps out when you have the caravan on the back ...

so all you need now is to find the right tail light feed which comes from the front and goes into the INPUT side of the bulb fail unit and connect brown wire to this ... if you connect the brown wire to left tail light wire it's going to overload the bulb fail unit ...

The left rear fog does have a lamp in as it also works as a tail light (no blank) but is not working, what I don't understand is the way things were the right fog couldn't (and didn't) have worked either.... I swear it used to + how did it ever pass an mot??? No cut out switch in the old 12N socket that am aware of and new skt is a standard one.

Now, as you say, to find the right tail feed. Do you know of anywhere I can access a diagram of the inputs to the bulb fail light unit?

Thanks again

[Brucie24]

Finally....

Sorted the car fog lights to work as should. Turns out the left tow side light was connected to the wrong side of the bulb fail unit so removed that and connected it to the input side of BFU and also the RH to the input side.

Whilst I was at it replaced all the scotch locks with proper splices and tidies up the looms. All working tickity boo now

Off at 2am this sat morn so Sunny (positive waves) Cornwall here we come.

Thanks so much for your input Clan it was a great help.

[Clan]

Glad all is well ! The rear fog light is not a MOT testable item ..
Have you got the stop lamps wired into the input of the BFU too ?
I hope the holiday is good i used to live in Helston :-)

[Brucie24]

Have just got back from two weeks in heaven now back to grind stone.

I did wire the stop lights to the input as well (they weren't). All worked well.

Thanks again for your help

Best Regards
Bruce