Fitting a tow bar tomorrow - advice required

[Bobby Dazzler]

????? How does that work when the ball is attached?

Perhaps Brian didn’t know it could be coded, and so having a removable towbar would avoid the reversing sensor issue when the towbar is not in use.

 

[Bobby Dazzler]

Where is this button located?

It could be different on your car but I have a button on the centre console on one of my cars, which disables the parking sensors temporarily.

 

[m80]

It could be different on your car but I have a button on the centre console on one of my cars, which disables the parking sensors temporarily.

Or like me, he is happy to turn the sensors off on the rare occasions he is towing, and the reverse sensors play up, when in reverse.

For my simple 7 pin I use one of these for testing,
can be useful for testing the plugged in whatever also.

7Pin Trailer Socket Tester Electrical Tow Bar Wiring Circuit Light Test Tool | eBay

This tester has one side to connect the 7-pins plug of a trailer and another side to connect the 7-pins socket of a car. This tester indicates quickly if a failure concerns the wiring of the car or the wiring of the trailer.

www.ebay.co.uk

I've no experience but

13 Pin Towing Trailer Towing Caravan Light Wiring Circuit Tester Plug Socket 12V | eBay

This adapter is a lighting and cable tester for trailers and towing vehicles. To do this, you simply have to insert the tester into the socket or plug to be tested, press the test button and a clear diagnosis is made via the LED display.

www.ebay.co.uk

 

[Petrol Pete]

So , post #20

The 7 pin socket is part of the MOT if you have a tow bar with or without ball fitted. Only not tested if the tow bar bracket has been modified not to accept a tow ball .

 

[BTB 500]

If the electrics are coded to integrate with the car electrics, there is no need to switch anything off. Where is this button located?

AFAIK a switch to temporarily disable Parktronic (for whatever reason) is standard fit ... certainly both our 2007 W639 and 2019 W205 have this.

You have not replied to my question in post#6. It would be good to know how a detachable towbar disables the rear sensors.

I just read that comment as meaning that when removed there's no potential for the towbar itself to trigger the rear sensors (although I think this is unlikely to happen anyway).

 

[JHS]

Perhaps Brian didn’t know it could be coded, and so having a removable towbar would avoid the reversing sensor issue when the towbar is not in use.

But having a removable tow ball will not in itself disable the sensors, which he implied.
In any case, the OP has a towbar with sensors disabled when the rack electrics are connected, so job done.

Of more concern is the MOT requirement. Every day is a school day.

 

[JHS]

It could be different on your car but I have a button on the centre console on one of my cars, which disables the parking sensors temporarily.

I have such a button but mine seems to disable the self parking function. The blue P on the display is extinguished.
I will have to check when the car returns this afternoon.

Edit to add: It seems that the button disables both Parktronic and Parking Pilot.

 

[BTB 500]

I have such a button but mine seems to disable the self parking function. The blue P on the display is extinguished.
I will have to check when the car returns this afternoon.

Active Park Assist will use the Parktronic sensors, so it makes sense that deactivating them would turn it off as well.

 

[JHS]

Active Park Assist will use the Parktronic sensors, so it makes sense that deactivating them would turn it off as well.

Just found that out.

 

[Bobby Dazzler]

But having a removable tow ball will not in itself disable the sensors, which he implied.
In any case, the OP has a towbar with sensors disabled when the rack electrics are connected, so job done.

Of more concern is the MOT requirement. Every day is a school day.

It’s easy to read two different perspectives from the same written words, often influenced by our own beliefs, experiences, and unconscious bias, and can be the source for disagreements.

Get a Brink, Westfalia or Thule one. Westafalia are the OEM ones. Get a detachable one so it doesn't set off your parking sensors. Make sure you get a 13 pin plug fitted. PF Jones in Manchester are very good. Supply and fit.

Because “detachable” was the focus of the sentence I interpreted it as meaning that detaching the towbar was what would prevent the sensors detecting an obstacle, rather than the sensors detecting a detachable towbar and then disabling the sensors.

 

[Margaret]

Thanks for all replies. I haven’t attached the bar yet but will do before the weekend. Just looking at buying a rack for 3 bikes. Need something easy to put on and remove. Is Thule the easiest ? They are quite expensive. Should I just head to Halfords ?

 

[br1anuk]

It could be different on your car but I have a button on the centre console on one of my cars, which disables the parking sensors temporarily.

That's the button that I was referring to. You would use that when the bicycle carrier was fitted to the vehicle so that the car could not detect the cycle carrier and give a false warning that you had inadvertently reversed into a solid object such as a wall or another vehicle. When the detachable towball is removed then there is no need to press said button to disable the rear parking sensors as they should only then detect objects which they are designed to detect such as walls, cars, pedestrians etc. If you need anymore information regarding the use of your vehicle please refer to the owners manual or seek professional advice regarding this subject.
I am not a trained Mercedes mechanic and my advice my not be right every time.

 

[ALFAitalia]

7 pin electrics are not part of the mot test, on a 13 pin socket it only needs testing if the ball is attached

Nope....the only time they are not tested is if the bar is rendered permanently unusable. Ball removed is not enough.
"If a tow ball or pin isn’t fitted at the time of test – because it’s detachable, it’s been unbolted or otherwise removed – but the attachment brackets are still in place, the brackets and towing electrics will still be assessed unless they have been deliberately rendered unfit for further use."

7 and 13 pins are tested....for a short while 13 pin sockets where not tested as the test device the stations were supplied did not work!! Wiring condition...IE exposed and damaged wires are also checked.

 

[ChrisHGTV]

Thule RideOn 9403 3-Bike Towbar Mounted Bike Rack706697.​

The above rack or similiar is what I am hoping to purchase. Tow bar is now fitted. All seems ok with the car. I’m told parking sensors will deactivate when rack connected to electrics. Looking forward to a day out with the bikes.

It might be worth having a look at Westfalia as well. I have a BC60 which is brilliant. You can get an extension for a third bike, and it folds so easy storage in the boot or garage etc. I did loads of research and went for the Westfalia. I think I actually got mine direct from them, they have 10% off at the moment. I’ve also got a Westfalia detachable tow bar and it automatically disables the reversing wotnots. All in very impressed with the setup. With the Westfalia you can also get a box that goes on it which seems pretty cool.

 

[Smiley]

I have had a couple of different makes of towbar cycle carriers and now have the Thule 3 bike carrier. They are expensive but they are better made and fit to the car better / more easily. The cheaper ones had irritating faults / design flaws - I can't remember what they were now but sufficiently irritating for me to buy the Thule. There is a good secondhand market for Thule when you no longer want it.

 

[Smiley]

Just to add I never had a Westfalia.

 

[ChrisHGTV]

Thanks for all replies. I haven’t attached the bar yet but will do before the weekend. Just looking at buying a rack for 3 bikes. Need something easy to put on and remove. Is Thule the easiest ? They are quite expensive. Should I just head to Halfords ?

Have a look at/chat with these folk
Bike carriers and bike racks | The Roof Box Company

They do all sorts. I was going to go for an Atera but then found the Westfalia which for me seemed the best for the money. It’s easy to put on, especially as it folds. It comes pre-adjusted and you just plonk it on the ball and lower the lever. Take the key out and job done. Quality is very good. Maybe not as fancy looking as Thule but feels more robust.

 

[ChrisHGTV]

Have a look at/chat with these folk
Bike carriers and bike racks | The Roof Box Company

They do all sorts. I was going to go for an Atera but then found the Westfalia which for me seemed the best for the money. It’s easy to put on, especially as it folds. It comes pre-adjusted and you just plonk it on the ball and lower the lever. Take the key out and job done. Quality is very good. Maybe not as fancy looking as Thule but feels more robust.

I should say it tilts as well so you can still get in the boot with the bikes loaded. Useful feature worth looking out for.

 

[Wolfie1]

Nope....the only time they are not tested is if the bar is rendered permanently unusable. Ball removed is not enough.
"If a tow ball or pin isn’t fitted at the time of test – because it’s detachable, it’s been unbolted or otherwise removed – but the attachment brackets are still in place, the brackets and towing electrics will still be assessed unless they have been deliberately rendered unfit for further use."

7 and 13 pins are tested....for a short while 13 pin sockets where not tested as the test device the stations were supplied did not work!! Wiring condition...IE exposed and damaged wires are also checked.

Nope....the only time they are not tested is if the bar is rendered permanently unusable. Ball removed is not enough.
"If a tow ball or pin isn’t fitted at the time of test – because it’s detachable, it’s been unbolted or otherwise removed – but the attachment brackets are still in place, the brackets and towing electrics will still be assessed unless they have been deliberately rendered unfit for further use."

7 and 13 pins are tested....for a short while 13 pin sockets where not tested as the test device the stations were supplied did not work!! Wiring condition...IE exposed and damaged wires are also checked.

dont know why its twice, whereas technically yes you are correct, the tester wont know if the ball has simply been detached or is completely unusable so best to air on the side of caution with that 1 and not test as that can open a can of worms, a lot of the vehicles we test at work have towbars and this is the route we go with it

 

[Bellow]

I have a factory fitted 'tow package' which is a tow bar (accepts Reese) but without the ball and, wiring (tucked underneath within bodywork) which is not connected to a socket.
Should I be getting failed at MOT for the lack of a functioning socket when there is a tow bar there?