Bizarre Rear Camera Issue

[lothian]

I'm t'shooting a Chinaseum-brand $30 license plate mounted rear camera. Yup... one of those POS things. The thing was presented to me as functional-with-a-caveat, and just one day prior everything was working as expected.

The Problem:
The Kenwood headunit automatically displays rear camera video when the car is shifted into reverse only when the trunk lid is open. When the trunk lid is closed, the headunit display goes black; iow, rear camera video cuts in and out when the trunk lid is moved up and down. This headunit has a "CAM" button to manually toggle display of the rear camera video when the car is in reverse, but video displays on the screen regardless of trunk lid position!

I discovered a broken solder splice within the black video cable at a flex point under the trunk lid. The video cable conceals three individual miniscule conductors. I delicately re-soldered each splice, wrapped each splice in heat shrink tubing (HST), wrapped the bundle in HST, then put the repair where it would never again be affected by trunk lid movement.

My careful repair promptly made the problem worse.

The New Problem:
The headunit doesn't automatically display rear camera video when the car is shifted into reverse regardless of trunk lid position; however, just as before I made my repair, the headunit displays rear camera video when the "CAM" button to manually toggled while the car is in reverse! I'm stumped.

I have no idea how to t'shoot this problem at this point. My limited understanding of these POS Chinaseum-brand $30 license plate mounted rear cameras is that switching is done at the headunit where 12vDC is detected via the "Reverse" conductor (within the headunit harness) that originates waaaaay back in the trunk from the reverse light.

I've checked--and re-checked--all conductors and splices.
What do I need to do?

Click to read more...

 

[hispls 5,000+ posts]

switching is done at the headunit where 12vDC is detected via the "Reverse" conductor (within the headunit harness) that originates waaaaay back in the trunk from the reverse light.

Often that sort of thing needs a ground signal (Parking brake does). How many wires come out from the backup camera?

Assuming your repair of the cable worked you probably just need to find a better source for your reverse signal. I'd try to isolate that and manually feed it the signal to see if you can get the camera to pop up on screen.

 

[lothian]

Picture is worth a thousand words. Here's the whole shebang, all laid out prior to installation. The answer to your question appears within.

The splice I repaired was in the video cable (top image).

I connected the red wire from the power cable (middle image) to the red wire from the video cable (top image) to a tap connector attached to the 12v conductor for the car's reverse lamp. I connected the black wire from the power cable (middle image) to a tap connector attached to the ground conductor for the car's reverse lamp. I connected the red wire from the other end of the video cable (top image) to the wire at the headunit labeled "Reverse". This is the extent of the power wiring for this camera, and everything worked as expected prior to the issue with failed splice.

Also, I don't think there's a "reverse signal" in this setup. I'm no electronics engineer, but to the eyeballs of this layperson, straight 12vDC juice flows directly into the "Reverse" wire at the headunit from the car's reverse lamp conductor via the red conductor within the video cable (top image). I presume when the headunit senses 12v on this wire (when the car is shifted into reverse) it switches the display to show the camera input signal. Again... it works (the display shows what the camera sees) when we press the "CAM" button on the headunit while the car is in reverse, but won't automatically switch to show the camera like it did before I made the repair.

 

[winkychevelle 10+ year member]

View attachment 41913
Picture is worth a thousand words. Here's the whole shebang, all laid out prior to installation. The answer to your question appears within.

The splice I repaired was in the video cable (top image).

I connected the red wire from the power cable (middle image) to the red wire from the video cable (top image) to a tap connector attached to the 12v conductor for the car's reverse lamp. I connected the black wire from the power cable (middle image) to a tap connector attached to the ground conductor for the car's reverse lamp. I connected the red wire from the other end of the video cable (top image) to the wire at the headunit labeled "Reverse". This is the extent of the power wiring for this camera, and everything worked as expected prior to the issue with failed splice.

Also, I don't think there's a "reverse signal" in this setup. I'm no electronics engineer, but to the eyeballs of this layperson, straight 12vDC juice flows directly into the "Reverse" wire at the headunit from the car's reverse lamp conductor via the red conductor within the video cable (top image). I presume when the headunit senses 12v on this wire (when the car is shifted into reverse) it switches the display to show the camera input signal. Again... it works (the display shows what the camera sees) when we press the "CAM" button on the headunit while the car is in reverse, but won't automatically switch to show the camera like it did before I made the repair.

The reverse switch wire is on the head unit itself. You would need to tap a reverse signal (possibly from the same place you tapped the red power wire) at the back of the radio. Assuming it's an aftermarket radio.

 

[Deiimos]

First I would measure the voltage at the reverse wire on the head unit, while the car is in reverse. According to a Kenwood manual, it likely does see the 12v+ from the reverse lights to trigger the head unit, so should be constant 12v+ while in reverse. I think most head units use a 12v+ signal from the reverse lights.

Perhaps a quick test if not good at measuring voltages, would be to manually send 12v+ directly to the head units reverse wire to make sure it triggers properly and switching the display. If it does work when force feeding 12v to that wire, then the reverse wiring where it taps into the reverse lighting is wrong somewhere. At this point I would run a new wire from the reverse lights to the head unit and not bother with the built in wire on the RCA cable.

 

[1aespinoza 10+ year member]

The reverse switch wire is on the head unit itself. You would need to tap a reverse signal (possibly from the same place you tapped the red power wire) at the back of the radio. Assuming it's an aftermarket radio.

The repair failed.