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I know this is an old thread but i'm doing the same thing and also found both reverse light wires are hot whenever the key is on. Adding the relay is not only simple but it works great. Thank you to the op for clearing this up. It is great info.
They only appear hot because it is a switched earth circuit - as are all the external lights on the Escape/Tribute AFAIK. So when OFF and you test for volts both side of the lamp you'll find 12V as the lamp isn't lit so no voltage drop across it. In short both sides are live but only fed from the live side...and yep a relay sorts out the switching you need for supplying reversing cams etc.
Found a possible solution elsewhere. It is for a camera and head unit, but will hopefully be the same principle!!!!
I figured it out if this can helps others that have a 2002 Mazda Tribute (or in general, a ground activated reverse trigger) needing to connect your Soundstream head unit or any unit that does not allow you change the polarity of the trigger from within the radios software) to work correctly with a backup camera, here is tail light relay wiring set of instructions and relay diagram that I pulled together from various sources. The backup display now works as designed in my vehicle.
The 2002 Mazda Tribute/Escape's reverse lamps work on a "ground activated circuit".
This means that the black and pink stripe Wire from the reverse bulb actually has 12V there at all time with the ignition switch in the run position, until the transmission sensor grounds this circuit when put in reverse gear).
So if you connect your camera red Wire directly to this wire, the backup camera will work backwards, displaying the camera image in all positions except reverse. The radio will also not function, staying in backup camera mode all the time.
Some head units have a function allowing you to reverse the trigger via its setup function, but if it doesn't you will need to use a relay.
Relay used in the below example: Amazon: Absolute RLS125 12-VCD Automotive Relay SPDT 30/40A & (optional): Absolute SRS105 5-Pin 12 VDC Relay Socket Interlocking Style:
Coil side of the relay:
o Connect a Power source to the coil side of the relay (pin #86 on relay, and Power source is orange /yellow stripe on reverse light which has 12v when Car is on ACC)- (ACC = power when key on)
o Then connect the other side of the coil side of the relay to the BK/PK wire pin # 85 to black/pink stripe of reverse light (which has 12v when Car is on but 0v when in reverse).
Then on the switch side of the relay:
o Connect the same 12v ACC power source to the switch side of the relay #87 (you will connect the same orange/yellow when car is on). Basically #87 & 86 are connected to the same 12v ACC constant power.
o Connect the other side of the relay switch (pin #30) to the reverse camera power (red) and the Soundstream head unit "cam control" trigger wire.
o Then connect the ground side of the camera to ground. The radio also needs to be grounded per the installation instructions that came with the radio.
So, now when you go into reverse gear, power is supplied to the coil (Pin #86) and then ground is supplied to the other side of the coil (pin #85) via the Black/Pink wire.
This creates a magnetic field which then pulls the switch side of the relay closed (Pin 87 connects to pin 30) and this allows power to flow to the camera and head unit 'cam control' trigger wire.
Thanks,I'm lost,could you show a diagram of connections,
Thanks,I'm lost,could you show a diagram of connections,
I made this diagram, plus an alternate one which keeps the camera powered all the time while the car is on (in case your head unit lets you access the rear camera without being in reverse for example), but won't switch to the camera and lock the screen unless you're in reverse (utilising the relay).
ORIGINAL:
ALWAYS POWERED/AVAILABLE WHILE CAR IS ON:
(Don't use with cameras that have their own LEDS unless you're fine with the LEDS always being on while driving. This would be distracting to other drivers!)
THANK YOU SO MUCH!! Thanks to everyone who contributed to this post. I had the same issues described above connecting an iBeam camera to a Pioneer head unit in my 2002 Mazda Tribute. The head unit allowed for me to change the polarity from Ground to Battery, but at best all it did was allow me to go to the camera during reverse and see behind me, but it would not work to send the reverse signal to notify the unit to turn the camera on (until I installed the relay!).
Since I had no idea what I was doing and it took me awhile to figure out what these numbers and diagrams meant, I wanted to post a picture of what my setup looked like after following the diagram. I also purchased a 40 amp 12V SPDT relay from Autozone, not the absolute one mentioned above and it worked fine. I tapped my backup light to the orange yellow and fed the red wire from the camera to the 30 pin. I simply zip tied the relay into the light and now everything works great!
Thank you everyone for contributing to this post, it actually helped me solving this issue. I could not understand why the reverse positive was continuously on. By the way any relay SPDT will do the job.
10-23-2018, 03:37 PM
