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Wiring an SPDT switch to manually turn on backup camera. Need help.

5K views 3 replies 2 participants last post by  fastbee 
#1 ·
So i decided to undertake this journey with a great wiring diagram, test light, and some general electronics knowledge. The issue i found is that i cannot determine which wire on the Radio C3 connector tells the display to switch over to camera view.

What i do know:
Pins 3&4 are the actual image from the camera.
The camera is constantly powered on, but something (tipm is my guess from researching) switches the radio to display the feed.
Pin 6, video signal 1, is not the signalling wire.
None of the pins in the C3 connector provide a testable current to switch the display to the camera feed.
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I could keep aimlessly cutting the wires until i find the one, but my concern is that if none of the wires apply a 12v current to trigger the change, would i eventually fry the unit by applying one (if i found the one that causes the display change).

Any info would be appreciated.
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The SPDT switch will be wired in (after cutting the signalling wire) with the lead going to the radio as the common pole, the other end will be on the NC pole for factory reverse signalling, and the NO pole will be a fused Aux Acc 12v wire for on demand camera.


FYI - getting the bezel off is a breeze with the split bench. Happy to disclose if needed.

Sent from my DROID RAZR MAXX using AutoGuide.Com Free App
 
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#2 ·
There most likely is not a +12V or even a ground signal that controls the switching if the unit is stock. Most (if not all) of the external controls for the stock radio are via the CAN BUS system...no voltages to check or introduce. The system works via different resistances that are introduced either by switches or the corresponding computer controller for that system. I don't have a clue what that resistance value would be. Also, be very careful with that test light...if it doesn't say that it is a "computer safe" test light, you could cause even more problems for yourself by damaging the sensitive circuits involved in these newer vehicles.
 
#3 ·
So then what i need to find out then (if i understand the can bus system) is which wire triggers the change in display, and the appropriate resistance. Then i would be able to snip that wire, place the end going to the radio on the common pole, split the other end and have the original wire go to the NC pole, and have the other split with inline resistors to the NO pole.

I guess then my only concern is that the manual switch may force the reverse lights on, or bug out some other electronics.
 

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#4 ·
No...typically no cutting of anything is involved, just hooking up resistors and relays to wiring. The CAN BUS uses a two wire system that is multiplexed throughout the truck. The easiest way is to get a CAN BUS interface, but I don't know if it would provide input for video switching. When I've installed alarms or remote starts in Dodge/Chrysler vehicles I've either used interfaces or had to use resistors of a given values on wires that serve certain functions (2.7k resistor is needed to make parking lights come on in some vehicles). One thing you might try is activating your reverse lights with the proper signal...might make video switch over. I think the reverse lights are typically just a +12V signal or use the proper resistance value to make them activate. Sites like Car Alarm, Car Stereo, Mobile Video, and Cruise Control Info for Installers might be a little better place to pose this type of question.
 
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