Peculiar rear view camera problem 2012 Passat - only works with engine off

[carnut11]

I have a peculiar problem with an aftermarket wireless reversing camera setup on my 2012 TD Passat. The camera works and gives a clear view when the engine is off. As soon as I start the engine, the rear view monitor picture shuts down.

The camera is powered by the reversing light wiring and needs 9v-30v to work. With the engine off and reverse gear selected, I measured 11.6v across the reversing light. With the engine going, I measured 11.9v across the reversing light.


So, the camera is getting power as needed but the monitor only works when the engine is off??


Totally baffled at this stage so suggestions welcome.

The kit was from Jaycar – Nextech QM3842

[MIG]

Is this a wireless unit? have you tried moving the screen closer to the camera and seeing if it still drops out?

Also, are you taking power and ground from the lights with your power feed? Or just power?

[carnut11]

Yes, wireless with a claimed 80m range. Both power and ground from reversing light. As it works with engine off, I suspect some form of electrical interference on the power line with the engine going. Being a diesel though I would expect less noise on the power line.

[MIG]

Try using better ground; the boot area has a few on either side. Just use the reverse light for power. Maybe temporarily test running the power from the cigarette lighter port to see if you get the same issue.

[kamold]

The 12v there is generally very noisy and needs a good filter to give a good clean feed. That should hopefully stabilize it for you.

[DV52]

@carnut11: As previously indicated, the voltage supply for the exterior lights is heavily embedded with a what's known as a "Pulse Width Modulation" (PWM) signal.

This means that for each external lamp, the normal DC (Direct Current) Battery volts is switched ON/OFF rapidly (switching rate is about 100 times per second). PWM is used to dim the lights when needed.

Anyhow - sometimes modern electrical gadgets get confused by the PWM waveform that's embedded in the 12 Volt power supply.

An easy fix if this happens is to buy an Electrolytic Capacitor and connect it across the power supply pins of the gadget (the best place for connection is as close as possible to the gadget) - this has the effect of filtering-out the PWM signal.

The exact specifications for the capacitor aren't that important - but it needs to have a DC voltage rating higher than Battery Volts. So I suggest that you select a capacitor with a rating either 16VDC, or 25VDC. I also suggest a rating in the range 680uf - 1000uf (for the sake of a quoting number)

Also, be aware that electrolytic capacitors are polarized - which means that they have a positive and negative lead. In the picture below, the (short) wire nearest the white band with "-" patch is the negative lead. So connect this wire to the negative power supply terminal on your camera. Of course, connect the other (long) wire to the positive power supply terminal on the camera

As I said, easy fix and the capacitor should cost about 50c - so very inexpensive solution too !!

Don

[adey88]

I had a similar issue, although not an ideal solution I used the built in cigarette lighter socket in the boot as a power source. Not sure if that's even an option for you.

Sent from my SM-G998B using Tapatalk

[carnut11]

Thanks kamold and Don. A filter capacitor did the trick. It is great t have a working reversing camera. Even though the Passat has great proximity sensors they don't cover every possibility.