Fitting Rear Parking Sensors to the A3 8V

[dch222]

Fitting Rear Parking Sensors to the A3 8V Body. 

Unimpressed by a quote from the Audi dealer of £600 to fit rear parking sensors to my 2016 A3 I decided to try and fit my own, although at the age of 72 I wasn’t as keen as I might have been a few years earlier. 

It turned out to be not too bad although I made a few mistakes which meant it took longer than it should have. You can avoid them by reading on.   

I bought a kit widely available on eBay for £12.99 not expecting too much, but on receipt everything looked fine. I tried it out indoors first up against a wall with a 12v power supply and couldn’t really fault it except that the sensors were black and my bumper is white. 

I was wary about spray painting them – afraid that the paint might clog up the transducers so did it very gingerly by holding them upside-down and spraying lightly from underneath from as far away as possible so the paint only just reached its target – several light coats rather than one deluge. 

So, no more dithering about, I had to get down to fitting them.  Photos can be found here:- - https://www.dropbox.com/sh/v0svck6jk7iavzj/AACtPnpyqSIeA7n8oVCHbGxNa?dl=0

I thought the fitting of the sensors and routing of the wires would be the tricky part but actually that was quite easy – the electrical connection to the reversing light cable was fiddlier.   

I tackled the electrics first because if I couldn’t achieve that and had to give up I wouldn’t want four holes left in my bumper.

The kit has to power up when reverse is selected so the task is to find which wire to the light clusters is the positive to the reversing light(s).

Mistake No 1 (and the stupidest). I removed the left hand light cluster (viewed from the back of the car) to sort out which of the three wires went to the reversing light.  Answer – none of them because the reversing lights are on the clusters on the boot lid which is a shame as it makes the job more difficult. 

The wiring harnesses from the car into the boot-lid can be seen on each side at the top near the hinges, but this is not a place that can be tapped into, I had to get access to the loom further down,  to the side of the boot. When the doors into the side panel storage pockets on each side of the boot are removed, the harnesses can be seen but they are near the top and access isn’t good.  I wanted to remove the whole trim to the left of the boot but could find no on-line advice on how to do this, and Haynes haven’t got around to writing a manual for the 8V yet it seems. 

I decided to have a look at the other side and on removing the little door saw that access was better as the loom extended lower into the orifice (always wanted to use that word in a non-biological sense) so I set to work to find which of the 20 or so wires in the loom was the one for the reversing light. There must be one there as there are reversing lights on both sides.  Wrong! That was Mistake No 2. 

My method for locating the correct wire was to stick a pin or sewing needle through the insulation of each one in turn to hit the metal strands inside and see which one had about 12V on it when reverse was selected (with ignition on), and DIDN’T have 12V when reverse was not selected.

This requires a couple of crocodile clips and leads and a volt-meter although a 12V bulb would do. One croc clip connects to the needle that you are shoving into the wire and the other to the car chassis (earth). Luckily there are earth points right next to the looms. 

Having done this to all the wires in the right had loom and drawn a blank I was forced to use the left hand loom where I eventually found the correct wire. On my car it was the green one with a red stripe.   

It was then a matter of cutting it and using a “chocolate block” to join it again and link in the red wire from the sensor control box power lead.  This I found very awkward due to the location but it may have been easier if I wasn’t left handed. 

I decided to locate the control box in the left hand storage pocket so the wires from the sensors would need to come in at that side of the car. There are two easy routes so no drilling involved. One is via the ventilation escape flap which is at the bottom of the pocket towards the rear of the car and the other is via a hole with a rubber sealing grommet which is probably there for this purpose on models which already have sensors fitted. This is at the bottom of the pocket towards the side of the car behind some packing. I replaced the grommet with a fancy cable gland but this is not really necessary. You could just make a hole in the existing gland which is removable. 

Before taking the plunge and drilling the holes in the bumper it is necessary to decide where to fit them. Jacking up one side of the car and lying underneath and looking back into the bumper you can see that there are some obstacles which need to be avoided but on the whole it is quite clear and there are even some handy supports that the cable can be laid in.

The instructions specify a height of 60 to 80cms but I found this to be too high (they would have been pointing upwards) so fitted them lower at 56cms. 

I decided that the best locations were 24cms and 66cms each side of the centre line of the bumper (but check this first in case there are variations).  I fixed masking tape vertically down over the bumper from the boot catch to mark the centre line and drew a cross on it at the vertical height a wanted the centres of the sensors to be.  Then it was a case of measuring left and right to make four more crosses on bits of masking tape where the holes were to be drilled. 

Good practice dictated that I drill small pilot holes before attacking the bumper with the hole-saw provided with the kit, so I zipped along the bumper with a cordless drill – 1... 2… 3… 4… 5… sh*t!    Mistake No 3 (maybe more stupid than the first one). Don’t drill a hole through the centre marker otherwise you will have to block it up with a self- tapping screw and paint it the same colour as the bumper. 

From here on it is fairly easy although awkward lying under the car and feeding the wiring along the inside of the bumper using the existing brackets etc to hide it behind and maybe the occasional tie-wrap.

It doesn’t really matter which order the sensors are plugged in to the control box.

I fitted the bleeper onto the top of the control box using the sticky pad provided and find that even though it is inside the storage pocket  and masked by the boot tray I can still hear it with the radio on, although if you listen at high volume you might need to locate it elsewhere. It is quite loud.

 

So, very satisfactory. The only minor complaint I have about the kit is that the power wire is rather thin with only a few strands of wire inside. This is all that is needed from the current carrying point of view but it does make it flimsy for connecting up. 

Tip.   You know how when you buy something and a few years down the line it goes wrong and you can’t get replacement parts because the company no longer exists or they have upgraded it and the bits are no longer compatible with what you have got?

Well at £12.99 just buy a second kit so you will have a complete set of spare parts.   

 

[CoventryAudi]

Theres a genuine after market rear sensor kit ive seen available on eBay for about £92. Holes to be drilled - crosshairs already marked on inside of rear bumper. 

Where are you located? Not too difficult to remove the rear bumper you will need a 10 mm socket (deep socket made by laser tools)

Torx bits for the screws in the arches

Dont forget to remove the clusters first and a black plastic locking wedge on either side

[dch222]

Thanks Mathew but I have already fitted my sensors - that was how I was able to compile the post!

I found I didn't need to remove the bumper but if anyone prefers to do that there is a good video on YouTube at the link below for the A3 8V body and the S3.