R170 SLK Reversing sensor installation

wiltsandy

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2001 230K SLK
Fitted a set of reversing sensors today so thought I'd post a 'how I did it' as others may find it useful.

Took about 4hrs to complete at a steady pace and was very straightforward.

The sensor kit came from Ebay for less than £20 all in and the sensors were pre-painted silver. I wasn't sure how good the colour match would be but it's nigh on perfect.

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The contents:
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I didn't want to drill the bumper so decided that the sensors would go in the three trim pieces. I also thought, wrongly, that there might be spaces behind this trim that the sensors would fit into but once the trim pieces were off it was clear that there weren't! It also meant that because I couldn't see behind the bumper to see what structure was there, it would have to come off.

Removing the trim. I used a plastic food spatula and small screwdriver to lever it out without damaging the paintwork.
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Trim pieces removed:
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wiltsandy

wiltsandy

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Part 2

Removing the bumper was straightforward, if a little fiddly. There are two studs in the rear box section which have to be undone:
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There is also a bolt inside each wing that has to be removed. These were really fiddly, especially the one behind the roof pump as there's not much room to get your hand in far enough to reach the bolt. You can just see it in the photo behind the pipe with the two red marks on it.
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One more nut and bolt through the front of each side of the bumper have to come out. These are accessed from the wheel arch. I didn't take any photos of these but they're easy to find.

Finally, the four plastic fixings, two each side, underneath the bumper have to be removed:
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Pull the centre out and then the fixing can be removed.

Once all the fixings are out the bumper can be removed. Slide it straight backwards as it slides in a fitting on each side. Don't expect it to come away from the car though as the radio aerial lead will still be attached.
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Bumper off:
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wiltsandy

wiltsandy

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Part 3

With the bumper off I could see how it was put together and it was clear that by fitting the sensors in the trim they would miss the aerial that was laid in the bumper. I put the trim pieces back in the bumper and slaved the bumper back on the car so that I could measure up.

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It's not easy to see the marks in the photo but the dimensions I settled on were 50mm from the trim join outwards toward the corners and then from these marks, 430mm back to the center of the bumper. Height wise, they were 30mm up from the bottom of the trim.

Pilot holes were then drilled at each mark with the bumper still on the car, before removing the trim pieces once again to drill the full size holes.

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I also test fitted a sensor at this stage:
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At the pilot hole positions in the bumper I drilled a slightly larger hole so that I could be sure that the sensors would fit easily without getting caught up. The sensor hole is 21mm and I used a 25mm holesaw for these.

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As the corner holes were where the large corner infill pieces are, these had to be trimmed with a knife to make room for the sensor body stiking through through the bumper. Trimming was just a matter of trial and error but quite a bit had to come off:

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The sensors were then fitted and the leads routed to the passenger side of the bumper as I decided to feed them through the empty grommet next to the aerial lead:
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wiltsandy

wiltsandy

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2001 230K SLK
  • Thread Starter
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Part 4

Now onto the control unit and buzzer.

The control unit was fitted with the supplied sticky pad to the inside of the passenger wing structure, out of the way of the roof mechanism:

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As there's no display with this kit (I didn't want one) there's only the buzzer to mount. I haven't fully decided where I'm going to fit it yet so for the time being it's stuck just below the first aid kit:

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The control unit needs an earth and live feed from the reversing light circuit. For the earth I simply put a ring terminal on the lead and fitted it to one of the studs that holds the rear light cluster on. The reversing light circuit is the bottom wire that goes into the multi-plug on the passenger side so I tapped into that. I think the cable colour was grey/pink but as I tested it with a DVM to find it I didn't pay much attention to the colours.

Finally, put everything back together and admire your work!:

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They work very well and give plenty of warning when reversing towards an object. I tested it against a panel fence and also against a toolbox on the ground. With the toolbox in front of the fence it picked this up first so I'm confident that that it will work well in car parks etc.

The quality of the kit is very good and the paint match excellent so in my opinion they're a very worthwhile investment!
 


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