Question for the MOT examiners.

[Ian21401]

How much of the tow hitch and associated wiring needs to be removed to negate the requirement to test the hitch and wiring at MOT?
Would removing the tow ball and wiring socket and tucking the wiring back into the body of the car suffice?

[Laird Scooby]

Originally Posted by Ian21401

How much of the tow hitch and associated wiring needs to be removed to negate the requirement to test the hitch and wiring at MOT?
Would removing the tow ball and wiring socket and tucking the wiring back into the body of the car suffice?

I might be wrong Ian but i'm fairly sure that if it's a 7-pin socket, they don't test the electrics, leaving just the main metalwork of the tow hitch. As long as that is sound (surface rust is ok but you may get an advisory for surface rust) then it shouldn't be a problem.

What is your actual concern on this?

[Ian21401]

Hello Dave and thank you.
My daughter’s XC70 has a 13 pin tow bar socket. It has been used for a few years without my problems, most recently lost autumn to return her caravan to the storage site. . She has a service plan with our local Volvo dealer which she bought when she bought the car. That plan includes an MOT as part of the annual service. The service was done yesterday and the car failed the MOT as the towing electrics were not working at all. So the tester as kindly issued a “FAIL” “Dangerous Fault, vehicle not to be used until repaired and updated DVLA accordingly. At present we cannot trace the fault so she cannot legally use the vehicle, even though it’s previous MOT does not expire until 23rd Feb.

[Laird Scooby]

Originally Posted by Ian21401

Hello Dave and thank you.
My daughter’s XC70 has a 13 pin tow bar socket. It has been used for a few years without my problems, most recently lost autumn to return her caravan to the storage site. . She has a service plan with our local Volvo dealer which she bought when she bought the car. That plan includes an MOT as part of the annual service. The service was done yesterday and the car failed the MOT as the towing electrics were not working at all. So the tester as kindly issued a “FAIL” “Dangerous Fault, vehicle not to be used until repaired and updated DVLA accordingly. At present we cannot trace the fault so she cannot legally use the vehicle, even though it’s previous MOT does not expire until 23rd Feb.

In that case Ian, i'm stumped i'm afraid. I know the 13-pin system has a lot more on it and that could cause problems elsewhere but the service plan should give some sort of cover for testing/fixing the towing socket i would have thought. The other thing that comes to mind is whether their socket tester is working correctly.

Have they done any software updates as part of the servicing? It's possible the CANBus system no longer recognises the tow socket if so - also if that is the case, it would be their fault for not correctly updating the software to include the tow socket, especially as it was working last time it was used.

[Auto Addict]

Originally Posted by Laird Scooby

I might be wrong Ian but i'm fairly sure that if it's a 7-pin socket, they don't test the electrics, leaving just the main metalwork of the tow hitch. As long as that is sound (surface rust is ok but you may get an advisory for surface rust) then it shouldn't be a problem.

You're NOT wrong. It's only the 13-pin socket that get tested for full electrical functionality. The physical, metal part of the tow bar get checked for secure attachment so any surface rust shouldn't be a problem as long as the tow bar is securely attached to the vehicle and not likely to fall off.

[Ian21401]

Thank you Dave and Auto Addict.
My previous understanding was that the MOT electrical functionality only applied to 13 pin sockets.
My humble opinion is that if the tow ball and electrical socket are removed, leaving only the actual tow bar (flange type) attached to the car and the wiring is withdrawn back into the vehicle bodywork so that it is not visible then there is no way that it would be apparent whether a 13 pin or 7 pin system had been, or ever was, fitted.
My daughter does not agree, stating that “if it is fitted it must work”.
My argument is that removing said items means that it is not fitted. Additionally, as the fittings are not there then there is no way that a trailer could be attached.
My reason for considering this action is so that a valid MOT can be obtained ASAP whilst the obvious fault is traced and rectified prior to the system being restored.
My daughter is a self employed pet sitter/carer and in normal times uses the car to carry her tools of the trade and travel between clients. Due to the present crisis her services are no longer required by the majority of her clients and her income has plummeted. As luck would have it she has one twice daily call each day this week due to the client being admitted to hospital for a follow up procedure. Fortunately I am able to transport her as required so all is not lost.
I have had an initial investigation of the car today. It appears that all three earths (pins 3, 11 and 13 ) are good and the permanently live pin 9 is live but there is nothing from any of the other pins. I am aware that the wiring is connected into the rear electrical centre on the left side of the load area, but as I did not fit it I do not know any details. In addition, when the electrics were originally fitted we were advised that it was not necessary to update any software. It appears that that was correct as the system has worked correctly for a few years until now.
I suspect that there is a fuse somewhere which may have failed and I will next be trying to locate the wiring connection into the electrical centre.

[Laird Scooby]

Your daughter is right Ian in that if it's fitted, it must work.

However, you are also right as if it's not fitted it can't be tested and if it can't be tested, it can't be failed.

What i would advise is to remove the actual ball hitch, try and find where the cable comes into the rear cabin and see if it simply plugs in - if it does (you may find there are two plugs on it, one male and one female, chances are wherever they plug into the loom when unplugged those two loom plugs will mate with each other) unplug it and check the functions of the rest of the lights.

Then try to find a way to remove it without damage to either the loom or the car.
That should enable the car to be tested and passed, then you/your daughter have a year to sort out whether it will work again, whether she still wants/needs it on the car etc.

Also time to investigate whether Volvo have done a software update on a routine service and forgotten to tell the car the tow hitch is fitted. Also if it's had a flat battery in between whiles it may have "forgotten" as well.
While it may not need a software update for the tow hitch to work, it might still need to be told it has a tow hitch. That's why i'm suggesting it's possibly had a software update during a service and the person doing it may have forgotten to remind it that it has a towbar.

[Auto Addict]

Originally Posted by Ian21401

Thank you Dave and Auto Addict.
My previous understanding was that the MOT electrical functionality only applied to 13 pin sockets.
My humble opinion is that if the tow ball and electrical socket are removed, leaving only the actual tow bar (flange type) attached to the car and the wiring is withdrawn back into the vehicle bodywork so that it is not visible then there is no way that it would be apparent whether a 13 pin or 7 pin system had been, or ever was, fitted.
My daughter does not agree, stating that “if it is fitted it must work”.

That idea would work just fine if you took the said vehicle for it's original MOT test with the tow ball already removed and the wiring securely hidden away as then the MOT tested will have nothing to test other then the security of the tow bar frame attachment to the vehicle. As the saying goes "Can't see... Can't test". I guess you could try your luck with your idea... although the MOT tester who is going to do your (one and only) free re-test will know what you did is to simply get an MOT pass. It all depends on how friendly and understanding the said MOT centre / tester are.

[Ian21401]

The car was first regd. in 2011, probably built in 2010.
I’m beginning to think that my initial reaction of removing said items is not a good idea. The FAIL is now a matter of history and is recorded and the car, minus the tow ball etc. would need to be tested at a different test centre and we would still need to trace and correct the problem eventually.
Re the software. It is my understanding that part of the service plan is a software check and update if necessary. The dealership is always reluctant to inform us as to precisely what service work has been done and we have to request the details.
No mention has yet been made of any software interrogation or updating at this service, however, dealership did advise us that the seat belt recall had been dealt with but did not elaborate as to what, if anything, had actually been done. I’m wondering whether, even if there was no actual software update done, if as part of the seat belt issue, the software was accessed and or updated and this has affected the tow bar electrics in some way, as Dave has suggested. It does seem to be a remarkable coincidence that the electrics worked a short while ago and following a service they have failed. I will have to consult with daughter with a view to contacting the dealer regarding this.

[37 RUBY]

Have you tried plugging a trailer in to check it really doesn't function.

I ask because I've had a similar scenario just prior to the latest draconian MOT rule changes.

The MOT centre whom I have been using for 15+ years plugged their testing equipment in and got nothing....which was strange as two days previous we'd towed our caravan to the workshop for service and Mrs37RUBY had checked trailer lights as we always do.
I went away thinking urgent repair was needed but when I plugged a trailer board I had, into the 13pin all was working.

It appeared that the test equipment was not compatible with the intelligent Volvo towing electrics. I took the car back with trailer board and demonstrated all was working.

Just worth a try. I also periodically clean out the socket with electrical cleaner and tighten the terminals as you only need half a turn of screw back and you lose connection. Awful things 13pin connectors.

....and for reference, here's the current MOT online section covering towing electric....https://www.gov.uk/guidance/mot-insp...ical-equipment

There is even a section with regards Canbus vs testing equipment functionality.