Switched reverse lights
I am going to add LED reverse (under trailer and bumper)lights, powered from the RV, switched through a relay from the tow vehicle 7 pin. This will turn the reverse lights on when the tow vehicle is i...
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Get a 12v automotive relay and hook pins 85 and 86 to the reverse wire from the tow vehicle and ground. It doesn't matter which pin goes to which wire.
Hook pins 30 and 87 to the battery and the light. It doesn't matter which pin goes to which wire. Do not use pin 87a.
Hook a ground wire from the light to the frame. Your backup lights will now work from the tow vehicle reverse pin, but still be powered by the TT's battery.
Now, take a 12v switch and hook its pins to the relay wires number 30 and 87. It doesn't matter which pin goes to which wire. Now, you can turn on the TT backup lights with the switch without the tow vehicle even connected.
This will allow no backfeed. The two hot wire sources are never connected.
Now THIS ^^^^^^^^^^^ will allow backfeed.
Hook pins 30 and 87 to the battery and the light. It doesn't matter which pin goes to which wire. Do not use pin 87a.
Hook a ground wire from the light to the frame. Your backup lights will now work from the tow vehicle reverse pin, but still be powered by the TT's battery.
Now, take a 12v switch and hook its pins to the relay wires number 30 and 87. It doesn't matter which pin goes to which wire. Now, you can turn on the TT backup lights with the switch without the tow vehicle even connected.
This will allow no backfeed. The two hot wire sources are never connected.
Lakeland Bob wrote:
When I mounted backup lights on my RV (and my boat trailer and utility trailer) I simply connected their positive wire of the LED back up lights to the 7 pin (center pin) of the 7 wire trailer connector.
On the RV I went to the junction box under the trailer, located the purple wire and spliced them together. Since the 7th pin was not being used and was cut short, I had to redo all the wiring to get a longer pigtail, no big deal.
As for the relay, why? Put the switch between the house battery and the positive wire to the lights, and don't use it while connected to the TV.
Or just use a jumper wire from the #7 pin (center) to the #4 pin and remove it when done.
Now THIS ^^^^^^^^^^^ will allow backfeed.
