Running a dash-cam off reverse cable

[xpfloyd]

can anyone tell me what cable is the reverse light live in the rear cluster? I want to wire up my reverse camera to only power on when I'm in reverse. At the back of the light there are 5 cables - green/black, black/white, brown, white/black, black/red

There isn't any exposed cable so I can't test

 

[Jp23]

Should be green/black on pin 2

I Made the connection inside vehicle less chance of problems at a later date

 

[xpfloyd]

Thanks. Where in the vehicle? Just further up the loom?

 

[Jp23]

Yes just inside behind rear of light

 

[xpfloyd]

Thanks again @Jp23

 

[Pauly]

You can pick it up in roof space, main loom runs along nearside front to back, i connected above rear wheel arch area

 

[xpfloyd]

I'm having a frustrating time here @Pauly . With ignition on and engine not started I can select reverse and the image appears on the screen. When I start my engine it lasts for a second or two then all I get is a black screen with interference.

I've got live to reverse light cable and earth to body chasis.

If I disconnect my live and earth to the camera and connect it to a cable that runs to the cigarette lighter it runs fine even with engine running so the issue is with the power feed somehow. Could it be poor earth through chasis?

Does anyone know what cable in pic above is earth?

I also used a short length of speaker cable for the bit that goes through the door flexi hose. Could that be the issue? I thought it would be fine as it's copper

 

[xpfloyd]

Ok removed the speaker cable and used the correct cable. Wire directly to cigarette socket and it works fine with engine running. Wire to green cable for power and brown cable for earth and it works when ignition is on but then cuts out when engine is started.

Confused.com

 

[xpfloyd]

Checked the power in the green cable with a voltmeter. It's live with reverse engaged. It stays live after engine is started and camera stops working, so the camera is getting power

 

[DaveyB]

Sorry matey can't help you, I am shi*e with vehicle electrics. Pauly has retrofitted the reverse camera to his van so should be the man to straighten this out for you.

 

[xpfloyd]

It's a complete puzzler @DaveyB , I'm using the exact same cable to switch between reverse live and cigarette socket live and it cuts out on the reverse live when the engine is started.

I'm now thinking I can wire it to an ignition live but was wanting to avoid the camera being powered up 100% of the time the ignition is on

Is there an ignition live I can tap into at the rear of the van?

 

[Pauly]

What camera have you got ?
Where are you connecting negative ?

 

[xpfloyd]

@Pauly Its a cheap ebay camera. It has 2 connectors on it - one for video and one for power. The power cable splits into positive and negative. I have connected the positive to the green wire on pin 2 behind my light cluster and have connected the earth cable to the brown wire on pin 4. The yellow rca video cable runs from the camera to my kenwood headunit. It has a red short length of cable coming out each yellow RCA connector and I dont know what they are for.

This setup works with ignition on and reverse gear selected. As soon as I start the engine it last about 2-3 seconds then I get a black screen with interference.

If I then disconnect the positive and negative from behind the cluster and connect it to a cable that runs to the cigarette lighter type socket it works fine with the engine running

 

[xpfloyd]

Further info I found on google. Someone on the VW Jetta forum had the same issue and wrote "issue was caused by using the reverse light wire to power the camera. VW uses PWS which causes the voltage to fluctuate. Changed to the reverse output from the PAC RP4-VW11 and it gave the camera stable power. I ended up using a relay to power the camera that's switched by the reverse output."

I wonder if these cheap 3rd party cameras are more sensitive to voltage fluctuations? That explains why it works with the live feed from the cigarette socket.

@Pauly - Can you advise what type of relay I would use if I wanted to run a live feed from my leisure battery to the relay and then to my camera and have it switched by the green live cable to the reverse light?

 

[xpfloyd]

Sorry for all the posts but I've had another thought. Could I run a cable from the camera to the rear of the head unit and splice it onto the reverse cable (the cable that tells the head unit reverse is selected). This would save tapping into the cable that powers the reverse bulb. In my head it seems like this would work but im not an auto spark as you have probably guessed by now!

 

[Pauly]

That would be a better way of doing it as opposed to installing a relay (which needs a feed from the front anyway), im not actually sure the headunit takes a reverse signal i think it senses over the canbus network not a physical switch live.
I would use the earth stud behind the rear interior panel for a negative (although you do have a negative in the tailgate if required but its a pain to get to) and if you are going to take a cable to the front of the van you can pick up a switch reverse feed from the PDC control unit mounted underneath your steering wheel, this is how factory cameras are wired although you will need a special crimp to insert the wire into the PDC control unit plug

 

[Absolut5]

Checked the power in the green cable with a voltmeter. It's live with reverse engaged. It stays live after engine is started and camera stops working, so the camera is getting power

It is the Bulb failure system causing the issue.. its best to run the camera off a ignition feed and just having the headunits reverse wire running off the green/black

 

[Pauly]

I take it back just looked at the wiring diagram for factory camera and it shows the reverse feed coming from the BCM not the PDC control unit.

 

[xpfloyd]

@Pauly @Absolut5 - Thanks both for your help. I just popped the head unit out and checked the "reverse" cable that feeds the headunit. It has 12v live when reverse is selected (The harness adaptor is from absolut5). Im now thinking I can just run a new cable from this reverse cable all the way back to the camera, that way it will only be live when reverse is selected but will mean I dont need to bother with the green live cable feeding the reverse bulb.

That sound ok?

 

[Jp23]

Probably better just powering camera via ignition positive and leaving reverse signal just for head unit