idigsnowboarding

I’ve got a ‘17 CS and am wondering if anyone knows how the +12V accessory pin on the trailer wiring is supposed to function on this car?

I recently rewired my trailer with a 7-pin plug so a wireless backup camera uses the +12V accessory wire. That worked great and it no longer has PWM interference issues (previously the camera rebooted every time I braked or used the right turn signal), but now the camera seems to stay on forever after turning off and locking the car. All other lights are off and function as expected.

I found one other post where someone said the Porsche computer decides for itself when to turn off this trailer accessory wire… but no other info. Does anyone have experience with trailer accessories staying on for hours after locking the car? Don’t really want to leave this plugged in over a cold night to find my car no longer starts in the morning.

drewcwsj

Do you have an OEM hitch? Check pin 3. This is running lights power. The car knows when the hitch is unplugged and probaby kills hitch power.

idigsnowboarding

I do have the OEM hitch. To be clear, everything is turning on fine; trailer running lights are on when my headlights are on and off when my headlights are off. I'd just expect the +12V power (black wire on SAE/RV 7-pin wiring standards) to eventually turn off (before the battery getting critically low), but it doesn't seem to. I left the trailer hooked up yesterday for about 5 hours (turned off & locked) and the trailer camera was still on when I came back to it. If that's normal operation, I'll just have to wire in a kill switch for it.

drewcwsj

If you leave the Cayenne hooked to a trailer overnight I would just unplug the cable. If your trailer battery is dead and you leave the car connected when not running you could run into an issue.

Basically the hitch is designed to power the running lights, trailer brakes and trailer jack. So you can tow a trailer with a dead battery or no battery. Use the battery disconnect to ensure the hitch isn't trying to charge the battery from the hitch. Oh and my trailer backup camera only turns on when the running lights are on. So turn the Cayenne lights from auto to off.

idigsnowboarding

Thanks for confirming! I didn't like having to turn on my headlights to power the camera or the interior lights on my trailer so I rewired both of those to the accessory wire instead of the running/clearance lights. I'll put in a kill switch so I can turn off the camera, but great reminder about the discharge protection switch! I'll have to check that out as another option.