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BMW 3-Series (E90 E92) Forum > BMW E90/E92/E93 3-series General Forums > Regional Forums > UK > Unable to find a ground connection in the boot



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      07-15-2020, 10:19 AM   #1
billabong02
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Unable to find a ground connection in the boot

Hi,

I'm trying to set up a back up camera on my E90. I've tested the camera via a 12v adaptor while connecting the video rca to my tv and it's all good, I see an image.

I've removed the trunk liner on the right side where the battery is to try find a ground connection but I'm unable get a connection anywhere while using the positive end of the adaptor. I get no image, nothing.

When I try connecting directly to the negative terminal of the battery, the camera starts to display static.

Does anyone know the best place to get a decent ground connection anywhere in the trunk?

And also, how do we test for a stable ground connection?? are there any tools I can use?

Thanks
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      07-15-2020, 10:24 AM   #2
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Drill a hole in the trunk floor? Ground to the negative battery cable, trunk latch, or any connector with a ground.

If you don't know how to check for a ground you should not be doing any wiring honestly until you understand the basics and at least have a voltage meter.
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      07-15-2020, 10:27 AM   #3
Emilime75
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Why are you using the positive from the adapter if you're testing with the car battery? Try both positive and ground directly to the battery.
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      07-15-2020, 11:04 AM   #4
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Quote:
Originally Posted by Emilime75 View Post
Why are you using the positive from the adapter if you're testing with the car battery? Try both positive and ground directly to the battery.
This might sound like a stupid question but is the car battery also 12volts?

I'm no expert, just a guy attempting some DIY.
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      07-15-2020, 11:05 AM   #5
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Quote:
Originally Posted by 9krpmrx8 View Post
Drill a hole in the trunk floor? Ground to the negative battery cable, trunk latch, or any connector with a ground.

If you don't know how to check for a ground you should not be doing any wiring honestly until you understand the basics and at least have a voltage meter.
I'm trying to learn the basics, this is my first DIY.
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      07-15-2020, 11:42 AM   #6
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Quote:
Originally Posted by billabong02 View Post
This might sound like a stupid question but is the car battery also 12volts?

I'm no expert, just a guy attempting some DIY.
Yes, it is 12v.

What will you connect the video from the camera to?
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      07-15-2020, 02:37 PM   #7
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Quote:
Originally Posted by Emilime75 View Post
Yes, it is 12v.

What will you connect the video from the camera to?
Thanks, that worked! I used the long rca cable to connect the camera to my TV.
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      07-15-2020, 03:02 PM   #8
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I meant in the car. Are you installing a TV in the car?
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      07-15-2020, 04:01 PM   #9
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Quote:
Originally Posted by Emilime75 View Post
I meant in the car. Are you installing a TV in the car?
No lol, I won't be able to fit a 40 inch TV in my car. I just hooked up the back up camera rca cable to it for a quick test to see if the camera works. I'm trying to link up a back up camera to my iDrive.
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      07-15-2020, 04:27 PM   #10
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So I’m surprised using the actual ground from the battery gave static but try the left side for a ground point. I’m sure there’s one that side.

So you can use the positive direct from battery and find a different earth point.

Does the camera not come with install instructions?
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      07-15-2020, 04:31 PM   #11
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Oh I just thought is there no where on the bootlid to earth it? I’m sure there is as the idea too with any component is to have a short run for the earth.
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      07-15-2020, 04:57 PM   #12
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You're going to have to do a lot of research on how to get a back up cam to display on your iDrive. You'll need an interface module between them and will need to do some wiring.

No offense, but the fact that you didn't even know that a car's electrical system is 12v leads me to believe this is way over your head. It's cool if you want to learn, but it won't be nearly as easy as you may think.
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      07-16-2020, 03:04 AM   #13
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Quote:
Originally Posted by Emilime75 View Post
You're going to have to do a lot of research on how to get a back up cam to display on your iDrive. You'll need an interface module between them and will need to do some wiring.

No offense, but the fact that you didn't even know that a car's electrical system is 12v leads me to believe this is way over your head. It's cool if you want to learn, but it won't be nearly as easy as you may think.
I'm using this DIY thread and bought everything I need:

hhttps://www.e90post.com/forums/show....php?t=1005301

- Posi taps and locks to avoid cutting and splicing
- The emulator
- The camera
- The K-Dcan cable for coding

I absolutely have no doubt that this will be a tough undertaking but I need a project for my sanity and I'm pretty optimistic I can get this done, I'm halfway there. Tell you what, if I manage to get it to work, I'll write my own guide to help people.

Last edited by billabong02; 07-16-2020 at 03:24 AM..
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      07-16-2020, 03:06 AM   #14
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Quote:
Originally Posted by RajB View Post
So I’m surprised using the actual ground from the battery gave static but try the left side for a ground point. I’m sure there’s one that side.

So you can use the positive direct from battery and find a different earth point.

Does the camera not come with install instructions?
What I was doing initially was completely wrong and wasn't closing the circuit because I was using the positive on the 12 adaptor and negative from the car battery. That's prolly why there was static...

Also, its a Chinese back up camera and it didn't come with instructions.

Last edited by billabong02; 07-16-2020 at 03:31 AM..
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      07-16-2020, 03:08 AM   #15
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Quote:
Originally Posted by RajB View Post
Oh I just thought is there no where on the bootlid to earth it? I’m sure there is as the idea too with any component is to have a short run for the earth.
I've managed to ground the camera, basically the whole body of the car is ground which I didn't know. I've wired my ground wire to one of the screws behind the boot liner where I've installed the camera that fits into the boot handle.
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      07-16-2020, 04:06 AM   #16
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Car battery may only be 12v but has a lot of amps!! take care with wiring and make sure you have a suitable rated fuse on the live lines.

and yes, body is the ground/negative. Is the case on nearly all cars.
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      07-16-2020, 08:12 AM   #17
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Quote:
Originally Posted by billabong02 View Post
I'm using this DIY thread and bought everything I need:

hhttps://www.e90post.com/forums/show....php?t=1005301

- Posi taps and locks to avoid cutting and splicing
- The emulator
- The camera
- The K-Dcan cable for coding

I absolutely have no doubt that this will be a tough undertaking but I need a project for my sanity and I'm pretty optimistic I can get this done, I'm halfway there. Tell you what, if I manage to get it to work, I'll write my own guide to help people.
Good, you're on the right path, then. Take your time with it and ask questions if you encounter something you don't understand. There's plenty of people on this forum that can help.
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      07-16-2020, 10:20 AM   #18
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Quote:
Originally Posted by Emilime75 View Post
Good, you're on the right path, then. Take your time with it and ask questions if you encounter something you don't understand. There's plenty of people on this forum that can help.
Thanks Emilime75, appreciate it!
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