To relay or diode, that is the question. Well, firstly you need to know what role each component will play in a circuit.

A diode is meant to conduct power in one direction and has the ability to allow currents to flow through or not depending on the direction.

Relays are switches that open and close contact points to other circuits basically controlling a circuit by a low power signal or to control multiple circuits with one signal.

So, if youre looking to add lights to a trailer or boat and be able to manually control them or have them come on automatically when youre in reverse, this diagram uses a relay:

Oznium offers a relay thatd work: https://www.oznium.com/wire-12v-and-relays/relay40

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## Extra Information

rpaxton

Here is my project: I am wiring a set of courtesy lights to a boat trailer. I want these lights to come on when the truck is in reverse and also be able to activate them with a manual switch in the cab. My concern with this setup is that most automatic transmissions are shifted electrically now, and I dont want to back feed the circuit and shift the tranny into reverse when I am not behind the wheel.

My questions is would it be easier / better to use relays wiring this circuit or diodes? Can anyone suggest a wiring diagram for this circuit?

Thanks in advance! Rodger

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Phil Oznium Owner

A diode would likely work (youd have to make sure you get a large enough one to handle the current). Or heres a nice diagram for you which shows how to do it with a relay.

Im assuming the stock reverse light circuit it positive switched (with a constantly connected ground wire).

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Comments (1)

Tony - May 14, 2020

How do you determine the size of the diode needed? Im trying to accomplish this however when I turn my switch on the reverse lights also come on even though I have a diode in place with the banded side facing the radios reverse trigger wire. Im using a 2 1 amp diode. On the banded side I spliced ties the two together going to the reverse trigger and on the other end (2 legs) one of my switch wires connected and the other leg is the camera/reverse light wire coming from the rear of the car. If I do it this way when I flip my switch the radios reverse trigger goes into camera mode but doesnt show an image since the camera isnt getting power. Any help is appreciated.