Reverse camera not working

**fcosenti** · 23-05-2014, 06:50 AM

Hi folks,

I have a Tiguan TDI 4motion 2012, and I have a very strange issue.

I usually purchase Chinese GPS units with reverse camera from eBay, since they are cheap and capable of being replaced with new models regularly. I had my mechanic successfully installing these $20 reverse cameras on a Toyota Hilux and Chrysler 300C, and they have been working for years without issues.

Now it comes the mystery - they do not work on the Tiguan. The camera gets wired to the reverse light, so it comes on automatically when reversing. When you turn just the battery on, camera works, image is perfect. As soon as the engine is started, picture appears, flickers then disappears. Camera turns off. A reverse camera that cannot be used while reversing - great.

I tried 2 cameras, wired and wireless, they both show the same identical issue. My mechanic connected a 12V battery to the same directly, and it works - but when taking power from the light (as designed), it works only with engine OFF.

What's wrong with the Tiguan? Is it a weird computer/CANBUS protection, detecting additional load on wire and doing something weird? How would I circumvent/fix the issue? Reverse lights are on, they do not flicker.

Has anyone successfully installed one of these cheap Chinese reverse cameras on a Tiguan, wired as described?

**Snail Style** · 23-05-2014, 07:06 AM

Reverse light is possibly duty cycled. So it only has a partial 12v signal. VW use a control unit which switches the voltage to the camera.

**fcosenti** · 23-05-2014, 07:24 AM

Originally Posted by Snail Style

Reverse light is possibly duty cycled. So it only has a partial 12v signal. VW use a control unit which switches the voltage to the camera.

So how would you fix this? How do I get a solid 12V signal while reversing? And why does it work when engine OFF?

**fcosenti** · 23-05-2014, 07:37 AM

I think I found my answer, and it sucks.

"The reverse signal in the Volkswagen Golf Plus, measured when the engine is not running, appears to be an actual 12V. On the face of it, there is nothing wrong with that. However, if the engine is running and reverse gear is engaged, the reverse signal appears to be duty cycle controlled! If this signal is used for a parking radar or reverse camera, for example, the customer could return with complaints that are difﬁcult to troubleshoot, even though everything appeared to be functioning properly during installation!It is only possible to determine whether or not a signal is duty cycle controlled by measuring the signal with an oscilloscope, which makes the pulses visible. If related functions in the car are operated (e.g. pressing the brake pedal) while the lighting signal is being measured for example, and the pulse width changes or the pulses disappear, you will know that a duty cycle control is being used. All of which brings us back to the old adage: to measure is to know!"

They really go to enormous lengths to sell their overpriced accessories. The nasty bit is that NON WORKING aftermarket ones are happily sold by unscrupulous people.

**tigger73** · 23-05-2014, 07:45 AM

I've installed a reverse camera into my Tig and there is a permanent feed off 12V power (I fed this off the accessories socket). It then uses the reverse light as a trigger signal only. That way you're not pulling extra current on the reverse lights circuit.

It possible that your car is detecting a fault on the lighting circuit due to excess power drain. Not sure whether there is a cut-out to protect things.

You can buy an OEM boot handle kit for around $200 landed from bold-sport: Bold-Sport.com :: OEM RGB Reverse Camera Kit for Tiguan, new passat B7, New jetta

I know I paid a bit less for a Chinese copy but I'd be confident that the bold-sport ones would work whereas the ebay knock-offs may be a bit hit and miss. Given that it's a reasonable job to put it in I'd probably pay a bit more for the OEM unit and not bother with stuffing around.

**tigger73** · 23-05-2014, 07:45 AM

I've installed a reverse camera into my Tig and there is a permanent feed off 12V power (I fed this off the accessories socket). It then uses the reverse light as a trigger signal only. That way you're not pulling extra current on the reverse lights circuit.

It possible that your car is detecting a fault on the lighting circuit due to excess power drain. Not sure whether there is a cut-out to protect things.

You can buy an OEM boot handle kit for around $200 landed from bold-sport: Bold-Sport.com :: OEM RGB Reverse Camera Kit for Tiguan, new passat B7, New jetta

I know I paid a bit less for a Chinese copy but I'd be confident that the bold-sport ones would work whereas the ebay knock-offs may be a bit hit and miss. Given that it's a reasonable job to put it in I'd probably pay a bit more for the OEM unit and not bother with stuffing around.

**fcosenti** · 23-05-2014, 09:13 AM

Originally Posted by tigger73

I've installed a reverse camera into my Tig and there is a permanent feed off 12V power (I fed this off the accessories socket). It then uses the reverse light as a trigger signal only. That way you're not pulling extra current on the reverse lights circuit.

It possible that your car is detecting a fault on the lighting circuit due to excess power drain. Not sure whether there is a cut-out to protect things.

You can buy an OEM boot handle kit for around $200 landed from bold-sport: Bold-Sport.com :: OEM RGB Reverse Camera Kit for Tiguan, new passat B7, New jetta

I know I paid a bit less for a Chinese copy but I'd be confident that the bold-sport ones would work whereas the ebay knock-offs may be a bit hit and miss. Given that it's a reasonable job to put it in I'd probably pay a bit more for the OEM unit and not bother with stuffing around.

I don't think it is a "protection" - the reverse light is duty cycle controlled. It means that the 12V go up and down, they are not constant and sufficient to power the camera. The proof is that camera works perfectly when engine is off and car put in reverse on battery power only. Do you have a diagram of how you installed the relay switch connected to the reverse light? Which type did you use? it looks like I do not have much choice, those "expensive" cameras all assume an in-dash screen rather than a floating GPS using a mini-jack as INPUT.

**tigger73** · 23-05-2014, 09:23 AM

Originally Posted by fcosenti

I don't think it is a "protection" - the reverse light is duty cycle controlled. It means that the 12V go up and down, they are not constant and sufficient to power the camera. The proof is that camera works perfectly when engine is off and car put in reverse on battery power only. Do you have a diagram of how you installed the relay switch connected to the reverse light? Which type did you use? it looks like I do not have much choice, those "expensive" cameras all assume an in-dash screen rather than a floating GPS using a mini-jack as INPUT.

Yes I have this connected to a RCD510. You can pick these up for $300-$400. You have to be careful to get the unit with RVC connector input.

Sorry I'm not sure the best way to resolve your issue without adding a relay/switch driven off the reverse light circuit and taking power from a constant 12V supply.

Sent from my iPhone using Tapatalk

**fcosenti** · 23-05-2014, 10:27 AM

No worries, I spoke to the mechanic and he said Monday will do what you did (take power from 12V socket, install relay on reverse light). Thanks for the advice, I learned something new today, "Duty cycle controlled" lights.