Do I need a relay?

I posted this question within a reply, but bringing to the top level as I need some electrical help.

I just wired up my DiodeDynamics SSC2 LED lights at chase lights.

• I connected them via a 15amp add-a-fuse instead of directly to the battery, so I don't accidentally leave them on if the ignition is off.
• For now, I'm using the default 'rocker switch' that came with the diode dynamics wiring harness.
• This all works great. There's no relay at all on this circuit.

Here's my question:

• I would like to buy one of the backlit 'tall' tacoma switches either from CaliRaised or CH4X4.
• They are listed as 3amp switches.
• My question is if I need to add relays into the circuit to deal with this?
• My hypothesis is no, because upon looking at the DiodeDynamics SSC2 LED specifications, it lists the current as follows:
  • Power (watts): Main Beam: 7.7, Backlight: 0.7
  • Operating Voltage: 9-16V
  • Current (amps @ 12.8V): Main Beam: 0.6, Backlight: 0.06
• I would anticipate that I only need a relay if the amperage of the lights was greater than 3amps, which it doesn't appear to be.

Can someone confirm my assumption, or advise otherwise?

Thank you

 

On paper that seems fine. I am curious though if those LED lights have much of an inrush current, which could wear your switch contacts out prematurely.

Maybe @Diode Dynamics can chime in an enlighten us?

 

All the switch should do is turn the relay on and off. You should not run the full current of the circuit thru the switch itself.

There are aftermarket fuse blocks available if you are planning to add more accessories. Don't just wire stuff up without understanding what you're doing to the electrical system though, that's a good way to have reliability issues and fires.

Use a relay.

This isn't my favorite site, but below is a link to a very well done vid covering the install process of switches and relays:

Toyota Tacoma Daisy Chain Harness for "Push Style" Switches (tacomabeast.com)

I wired my switches up using those harnesses and relays connected to an Overland Equipped auxiliary fuse panel. If you're going to do things, do them right.





Link to my post when I added switches: https://www.tacomaworld.com/threads/drizzohs-21-off-road-build.748190/page-9#post-28364774

 

You will note that CH4x4 has a disclaimer that ALL switches must control a relay. In their FAQs they have a note that the most common problem they see is customers frying their switches because a relay is not used. I just wired up winch bumper lights and ditch lights this weekend, not a big deal if you do your research.

I don't wire positive from the battery through my switches, the only power my switches have are from the dash light circuit to power the lights. All my switches do is complete the circuit to ground. One side of the switch comes through the firewall from the relay, the other connects to the chassis ground behind the driver's kick panel.

85 - Coil Ground -- I wire this to one side of the switch (Green if you are using CH4x4 switches)
86 - Coil Trigger (POS) -- Wired to 30
87 Normally Open - Wired to the Load (Bumper or Ditch Lights or Whatever)
87a Normally Closed - Not Used here, just cap it
30 Common Connection to 87 and 87a -- Wired to your battery with a fuse or through an AUX fuse panel

Easy peasy. Only thing you need to do is figure out a spot to mount your relay. With ^ setup your lights or whatever load you connect will normally be off and when you push the switch it will complete the ground circuit, which will latch the relay coil and power your device. The relay handles the load and your switch does what it was built to do, be a switch.

Holler if you want pics and the diagram I drew up. It isn't the only way to wire up a relay, just the way I like to do it. You can have positive triggers as well.

 

Thank you for your replies. It seems I've split the room.

I saw the CH4X4 disclaimer as well, but I'm not really a fan of unnecessary complexity/wiring. I don't blame them for suggesting that, but I anticipate thats because many people are wiring up 60A lightbars, winches, airpumps, etc which draw higher amperage.
My understanding is that a relay protects the switch from damage by passing the higher amperage through the relay instead of the switch. While I can see this applying to most peripherals, the Diode Dynamics LED pods are pulling less than a single amp.

This is why I'm doubling down on the question.

 

I typically lean toward adding a relay because they will last longer than a low rated switch on most automotive loads.

But, an automotive relay pulls 150-200mA by itself, and requires additional wiring and connections that can be failure points. If the LEDs really only pull 600mA total and they don’t have a serious inrush (some LED drivers pull 100x the running current at startup), I would lean toward just having a switch for simplicity.


Does the switch from diode dynamics have any markings on it that indicate it’s ratings?

 

I'd still use a relay. Its a safety thing. Not just for nominal current, but it adds another barrier of protection against ground shorts.



Edit - same goes for fuse blocks. Heck, my block cost me 10 bucks. But it keeps the stuff organized, easy to troubleshoot, and well away from the stock electronics.

 

An alternative is to run a panel like the auxbeam that has the switch and relays built in if you would like to avoid wiring and mounting standard automotive relays in the engine bay. I shrug at your unnecessary complexity / wiring comment, but that is just a matter of perspective I guess. I used to fabricate 30 and 40 pin control cables and work on radios for a living so I jump at the opportunity to wire something with 5 pins.

All good in the hood.

 

To be honest, I didn't read every post above so there may be redundancy

There is some key missing information in your request....

how many lights did you actually install? The specs you provided are for a single light (per DD page).

While you currently have it set up to only have power to the lights while the truck is on... you must understand as voltage drops, amps will increase. Google/search for Watt's Law and that will provide an explanation of what I mean.

The 15amp fuse should actually be a smaller size fuse.... probably 5 amps if you only have 2 lights powered

I will always be in the camp of having a relay. You sort of need to plan for future lighting upgrades and/or replacements - within reason.