Need help: 2 reverse cameras to one monitor

Need some help. Couldn't find a similar post or search result on google to help me. Also if this is in the wrong section, moderator please put where appropriate.

So I have a 2008 Sport Tacoma. Pretty familiar with basic wiring. But here is my problem. I have an aftermarket 5in stand alone monitor (not part of the radio console). I already connected an aftermarket reverse came. The monitor and reverse camera are both powered by the reverse power light. So it remains off until I shift in reverse.

I added reverse camera to the front now. I thought I would just be able to use an add a circuit to my fuse block then to a switch. Also since it on the fuse it would only be able to switch on when my truck is on. I then connected a power cable from the ACC part of the switch to the front camera and monitor. That way when I power on the switch it powers the front camera and monitor.

Since I'm using the monitor for both the reverse and front camera, the monitor already has a power wire from the reverse light as mentioned. So I basically created a "Y" wire with two sources of power into the monitor. I figured since the wire from the reverse light is only on when I shift into reverse it would be an issue have another source of power from a switch.

I tested it out and it seemed to work. However I only tested with the ignition to the ON position and not when the truck was actually started. When I started my truck and turned on the switch to the front camera, the power wire that went into the monitor backtracked and went into the reverse wire making the R (reverse) on the dash light up while at the same time i was in Park. Also it triggered my check engine light.

Any ideas on how to make this work. I basically want to be able to have one monitor for a reverse cam and a front cam. I want the monitor and reverse cam to turn on when I shift into reverse and turn off when I am not in reverse. Then I also want the same monitor and the front camera to turn on when I flip a switch. Any ideas on how to do this without backtracking power to my reverse wire?

I know this was long winded, but any help will be greatly appreciated. there has to be a switch or wiring diagram out there to do this.

thanks in advance.

 

2 cameras on 1 input.

 

2 power sources with no backfeeding of the power using 2 diodes.

 

Thanks. I saw this item. I think I would still need some switch or relay so that power won't backtrack to my reverse wire when my front cam is on.

 

Thanks. I'll look into this. I never thought of this method. I knew there had to be something out there to prevent the backtrack of power, just didn't know what it was called. I'll definitely look into this method.