Journey electrical question

Adding a backup camera to a 2017 Journey. Sounded pretty simple. Got everything hooked up but not working properly. Tapped into backup light wiring to power camera when shifted to reverse. Image on screen blinks but does not work. I put a volt meter on the + & - wires going to the bulb & getting fluctuating readings between 11 & 12 volts. If I hook the camera wires to a 12v battery everything works. Seems like I am not getting a strong 12v from the bulb wiring. Any ideas?

You might move the meter upstream till you reach the connection that has a steady 12V then check/clean the connections downstream from that point to hit the bad one. Confirm a good ground path also.

When I installed the back up camera on my 2012 Ram I had to have the dealer update the computer to recognize it correctly.

Aftermarket or factory system? Some of the aftermarket ones have switches on the box that gets installed behind the screen that need to be switched depending on system.

Aftermarket. Did not see any switches. Connection is about 2 feet from bulb. I removed the bulb & attached wires to the bulb contacts to test & same issue. Looks like inside structure of hatch is plastic or fiberglass so can't ground to it so as a test I grounded to a bolt on hinge but did not change anything. I am thinking it has something to do with the body control module because the voltage seems to fluctuate??

You could try using a relay. Use the "back-up" signal to enable the relay's coil (85 or 86 (with a good ground on 86 or 85)). Fused battery feed to contact supply (30), then the other contact (87) out to your camera's +12V input.

Will try and let you know. Thanks