Relay Question

[gallagher073]

Here is what I want to do:


I added two utility lights to my back rack


I want to wire them so the new utility lights come on automatically with the factory reverse lights.


but


I ALSO want to trigger the utility lights manually with a switch without the factory backup lights coming on.


The truck is a 2005 GMC Sierra


I'm not sure how to wire this with a 5 pin relay.


Any suggestions?

 

[Torpedo]

Pin 30 Unity pair


Pin 85 Ground


Pin 86 BU lights


Pin 87a Wire from your unity's only switch + good for 10 amps.


Pin 87 Fused + good for 10 amps.


Also a really good idea to place a 1004 diode across 85 and 86 with the line towards 86(+) to arrest field collapse to protect body computer.


The fused 10 amp wire can power your switch and the relay.


This is all provided your vehicle throws a hot to backup lights to switch them on. Most do.

 

[ERM]

Here is a better representation of what he is trying to say. Everything in the box outline are the internals of the relay.


Connect your lights to terminal 30 of the relay. Connect your appropriately rated switch to terminal 87A and AFTER your fuse. Connect your fused supply to terminal 87. Terminal 85 will be connected to ground and terminal 86 will be connected to your reverse lights.


The diode he is referencing is actually the 1N4004 diode, available at Radio Shack. If you're not sure how to connect the diode, you'll notice it is black with one end marked with a grey stripe. This is the side that connects to the 86 terminal and the other end to the 85 terminal. This diode will filter the current spikes generated by the magnet in the relay. Since your relay is connected to your reverse lights, you don't want the spikes back-feeding into your vehicle's electrical system.


Let us know if you have any other questions.


Tony

 

[MtnMan]

With apologies to ERM for horking your diagram, it can also be done with a regular 4-pin relay:

 

[ERM]

With apologies to ERM for horking your diagram, it can also be done with a regular 4-pin relay:

You can, but it's just easier using separate connectors, rather than joining the switch and light wire into one connector. If you ever have to take anything apart, you don't have to cut wires. Also, I was just giving a visual to Torpedo's text. Either way, both methods work.

 

[eng18ine]

this is why i love this site. everyone comes together to help one another.


this thread helped me do the same to my truck. thank you to all who helped!

 

[Torpedo]

Hey ERM, Thank you for cwarification on the diode number. Memory aint what I remember it once being. Good catch.


:thumbsup:

 

[gallagher073]

thanks for the input worked like a charm! :thumbsup: