Parking Sensor fitting (Cobra R0394)

[monopoly]

Okay so here's my experience of installing flush-fitting parking sensors (Cobra R0394) to my Leon SE. The actual fitting took about 2-3 hours, but I spent a few evenings prior to that spraying them up to match.

Stuff I bought:

• Cobra R0394 flush sensor kit - (eBay ~£75)
• Paint kit - primer, paint and lacquer (Paints4U - £23)
• 17.5mm Q-Max metal punch (eBay - £12)

The punch is a lot easier than drilling the sensor holes. The instructions recommend a 17mm punch but I was unable to find one except for the "official" Cobra one which (surprise, surprise) is £30 more than a 17.5mm one which is widely available. I practiced on a few scrap bits of plastic and found 17.5mm to be a perfectly good, snug fit.

Wiring First:

Take a feed from the reverse signal wire which is part of a loom which runs up over the near side rear wheel arch, behind the plastic trim at the side of the rear seat. Removing that trim is a matter of pulling it inwards at the top end (towards the opposite door), then upwards from the bottom. There is a plastic nut hiding at the back of the rear seat bench which you can just about get to without removing the rear seat bench. Scraped knuckles!

Unwrap the loom and take the positive feed from the BLUE/BLACK wire. I scraped away some insulation, soldered my feed on and wrapped it up again, but you could use a Scotchlock connector. For the ground wire, there is a convenient ground point up inside the body on the way through to the boot. The Cobra kit comes with a ring terminal already on the wire so you can just remove the nut from the ground point, drop it on and replace the nut.

You'll also need to remove some trim in the boot:

• Lift out the boot floor and put aside
• Remove the large piece of plastic trim which covers the lock stay. It just pull upwards - you have to be brave!
• Remove the single torx screw in the plastic trim at the side. This should give you enough play to peel back the nearside carpet. In the void behind the carpet you should find spaces to stick the sensor ECU and Buzzer, and a convenient grommet through which you can bring in the sensor wires (pic below)

Sensors painted up and ready to go:

Removing the rear bumper:

This was the part I was most worried about but actually it was very easy.

• Remove the rear light units. This is covered in the manual and is very easy.
• Remove 6 torx screws from the underside edge of the bumper - just next to the exhaust silencer
• Remove 4 torx screws in each wheel arch. 3 rearward-facing at the back edge of the arch and one facing upwards. Bit awkward to get to without the wheel removed, but doable.
• Finally remove the four torx screws (2 per side) that were hiding under the light units. Note there is a single cross-head screw visible which does not need to be touched.

With all screws removed, carefully pull the bumper sides outwards from the wheel arch. It will come free and you can then pull it away from the body with minimal force. Don't pull it too far - you need to disconnect the number plate lights.

With the bumper removed, you'll find it is already marked up with crosshairs for the sensor positions - great!

Drill a 2mm hole at each point so you can locate them from the outside

From the outside, drill the holes out to 8mm to allow the punch bolt to pass through:

Use the punch to make the final-sized holes. Make sure the punch is cutting from the OUTSIDE! :

Finally use a sharp blade to tidy up any swarf on the inside of the hole.

Fit the sensors into the holes as per the Cobra instructions, making sure to clean and prep the bumper thoroughly.

Sensors stuck on and wiring tidied up:

Offer up the bumper to the car and pass the sensor wires up through the grommet on the nearside. Don't forget to reconnect the number plate lights!

Re-fit the bumper with one screw each side to test the sensors before replacing the remaining screws.

 

[Orbiter]

Great write-up, thanks for sharing your experience with this. The small sensors look very neat too; Btw, did you have to paint the edge of the holes you cut, or do the sensor's have some sort of collar that covers the raw edges of the holes?

 

[monopoly]

No, that's the main advantage of using a punch rather than a drill to make the holes. As it pulls its way through the plastic from the outside, it turns the edge of the hole inwards; only a tiny radius, but enough to hide any unpainted inner edge.

 

[dw911]

Great write up, thanks for taking the time to write it up.

Maybe stuff like this and all the other good write ups etc should have their own section or stickyed, as they tend to get lost in amongst all the other general posts

Or maybe be put into the FAQ section, which at the moment seems to be for the most part little more than a mini me mirror image of this section and serverly lacking in FAQ's

 

[Mr Pig]

This is really helpful info and definitely should be in a dedicated help section. Thank you.

 

[kevster184]

Great guide! I've taken what i need from this to fit my RVC, just to confirm the reverse positive feed is the BLUE/BLACK wire.

Where the Blue is the main colour and Black is the stripe?

I ask because the black in this colour format appears bolder type face...

 

[monopoly]

Sorry I can't remember which is the main colour - the bold type is not significant.

You'll probably find like I did that there's two blue/black wires in the loom passing over the wheel arch. God knows why they repeated them! One is the reverse signal, the other (I think) is the rear fog light. It was trial and error for me to get the right one.

Note that neither receive power when the boot is open!!

 

[kevster184]

Thanks for coming back. I went for the first one i found which i tested and works with reverse selected. Yes indeed the boot lid open cuts power to all lights on the lid....

Now when i start the engine the camera gets some kind of interference but its ok with ignition only. So problem solving....

 

[Mr Pig]

I have the official fitting instructions here for the approved after-market reversing sensors. One thing that might be on note is the fact that it says to put the car in neutral and disconnect the battery before doing this and to make sure it is in neutral before reconnecting the battery. Does it matter?

 

[monopoly]

I have the official fitting instructions here for the approved after-market reversing sensors. One thing that might be on note is the fact that it says to put the car in neutral and disconnect the battery before doing this and to make sure it is in neutral before reconnecting the battery. Does it matter?

Sounds like good practice to reduce the chances of shorting something out or blowing a fuse.

I was in neutral anyway, as a starting point before powering on the sensors.

Must admit I didn't disconnect the battery though, but was careful not to short anything.

 

[kevster184]

Just measured voltage from the blue/black wire. 11.6v with ignition on only, 11.4-11.6 variation wiith engine running. Will test another source.

If this is the issue i don't know where else to find a source for reverse bulb power only. (Camera says not to be on constantly or it overheats)

 

[monopoly]

Are you saying it's constant ~11.5v even when not in reverse?! If so, that's definitely different to mine.

You could go downstream and take the feed from the actual bulb unit in the boot lid. I think it was grey/white where it terminates. You'll have to take the boot lid trim off though and feed your cables down the rubber tube into the headlining..bit of a faff.

 

[kevster184]

Sorry no, only power when in reverse.
Tried an alternative, positive from cigerette lighter is 12.1v when in reverse and with engine running it increases to constant 13.6 ad you'd expect. Camera works perfectly!

You definitely had 12v? Camera doesn't like the lower variation but is ok at 11.6. Maybe park sensors were ok with this. How odd.

I'll keep thinking!

 

[kevster184]

Your right the grey/white is reverse bulb. Continuity from the wheel arch wire to this is ok, but also show continuity to the brown earth at bulb holder and a slight detection on the side/brake line.

I have LED rear lights. The reverse is a filament.

 

[kevster184]

You'll probably find like I did that there's two blue/black wires in the loom passing over the wheel arch.

Only one. Follow this through the loom that goes up to boot lid, blue/black matches the wire to the fog bulb?

Proper confused now

 

[kevster184]

Ended up with more help from thr RVC thread. Power from reverse feed is no good for RVC. Having to use a relay

 

[Mr Pig]

I've just fitted the Cobra kit to my car which is an ST. I thought I'd post a few tips specific to the ST as it differs slightly from the hatch.

The extra length of the bumper means more screws to remove from the underside, including two sneaky horizontal ones either side of the spare-wheel recess.

The sensors are supposed to be positioned so that the cable exits from them straight down. The centre two sensors don't have the clearance because of the number-plate recess so should have their cables pointed straight up instead.

The cables from the sensors to the grommet/hole where they enter the body are hanging in the breeze on the ST, there is no under-body cover on that side of the car. I recommend taping the cables together and after installation is complete you will still have access to them under bumper. There are a couple of convenient plastic flanges on the inside of the bumper. You can drill a couple of holes in them and cable-tie the sensor leads to them to keep them tidy. I used reusable ties because they'll need unclipped if you have to take the bumper off again.

Access inside the car is quite easy. The upper plastic trim panel, the one the blind slides in, is held on with two Torx screws, one under the seat release lever and one in the hole the blind fits into. Once removed the panel just pulls outward from the back edge. By removing the two plastic trims on the floor at that side as well you can pull the upper plastic trim and the carpet out far enough to give you all the access you need.

The wiring loom comes over from the front of the left wheel-arch into the space at the rear so you can make your power connection at the rear of the arch. There are TWO blue/black wires in the loom! I found that both showed voltage when reverse was engaged but only one of them would fire up the sensors. Don't ask me why, you just have to try them both.

In this space behind the arch you will also find an earth bolt on the body near the top. Ideal for connection of the sensor earth strap.

There is a grille on the underside of the big plastic trim you've pulled off. If you put the sensor buzzer on the bodywork just above it you'll hear the buzzer through the grille.

A couple of other tips.

When fitting the sensors to the inside of the bumper you need to adjust the depth so that the faces of the sensors are flush with the surface of the bumper. Try to set them flush or slightly low. If you end up with them slightly proud of the bumper they are more noticeable when viewed from an angle.

When removing the tail lights from the wings, they do NOT pull straight back! They will come out if you pull them straight back but it's very hard to get them out and you might break the clips. The lights pull out at about 45-degreees away from the car and should pop off quite easily. Remember to take care as the light wiring cable is quite short.

The Cobra punch is 17mm but if you can find a 16mm one I think it would give a better finish. Not tried this but the sensors are not a tight fit in the hole. Also, on a white car the insides of the holes are visible. Not a deal-breaker but if you have the time to run a lick of paint around the insides of the holes it might give a cleaner look.

Hope this helps.

 

[Marouane55]

monopoly YOU MADE GOOD JOB

me too i will do the same thing in may car but i have a question before i start

the Placement of the + reverse light if you can post a picture for the cablage

thanks for helping

 

[Mr Pig]

the Placement of the + reverse light if you can post a picture for the cablage

Inside the left of the boot you will find the loom with all of the wires in it. Peel open the loom and look for the black and blue wires. I don't know why but my car has two and they both power up when you put the car into reverse. Oddly, one of them made the reversing sensors work and the other didn't. I can't understand what that would be, maybe I made a mistake when I tested them, but just wire the sensors to one of the blue/black wires and see if they work.

 

[Marouane55]

Thanks Mr pig for the responce and the help

For the rear cobra parking sensors NOW it's Ok

But i will instal also the front cobra f0394 , to wire it it's the same positive black_blue ?