k4ylr

So electrical is a little out of my wheel house but I think I've got enough overhead to safely run this set up but I want to have it double-checked.

2 x 18W (1.3A) LED floods
2 x 25W (1.5A) LED spots

Can I safely wire these to a switched relay circuit that's 16GA rated for 16A? They relay is 30A fused on a 40A 4-pin relay.

I planned to gang them in pairs (25+18) to balance the load off the DT connector rather than 25/25 and 18/18. and run the pair of connectors to a dual output harness terminated at a single rocker for the entire set of 4 lights.

25W light for reference

18W for reference

Harness for reference

By my napkin math I have more than enough head room with the lights drawing ±76W @ 13.6V and a current draw of ±6A for the circuit and each LED light leg would ask for 38W @ 2.8A.

peligro113

You will have a total load of 6 amps for the lights, you only need 18 AWG for that load, but if you are using a 30 amp fuse for the relay I would use 16 AWG from the battery to the relay. The 40 amp relay is overkill for a 6 amp load but it will work. I would however run a separate smaller fuse for the lights, like a 7 amp fuse. There are TWO power circuits, control and power meaning ideally two fuses.

It doesn't matter how you separate the lights if you are using one relay, the amperage is still the same 6 amps.

The route should look like this:
power>30 amp fuse>relay>7 amp fuse>load

One thing I am 100% sure of though, is that you can't use a suppressor as a wiring harness.

Waynerd

I have asked similar lately. I'm running two 100w and two 50w. I have been told they will work fine with factory alternator specs. Lights are drawing between 25 and 30 amps total. Using 1 relay per light and a single switch for each pair.
Not sure if you mean running all 4 lights through one relay? Even if so you are well below the max rating of the fuse and the relay. Myself I would use a lesser amp fuse. And by my math you would be at 86watts total. 43 watts per pair. About 6.32 amps total draw and half of that per pair respectively.
I must state that I'm far from an expert. I'm not sure exactly how much to overrate a fuse but I would assume you don't want a 30 amp fuse when you're only pulling 6.32 to start with. I would think 10-15 would suffice.

peligro113

Fuse rating

How To Calculate The Fuse Rating
Using the guideline that the fuse is rated at 125% of the normal operating current.

Power (Watts) = Current (Amps) x Voltage (Volts)

Therefore:

Current = Power/Voltage

Therefore:

Fuse rating = (Power/Voltage) x 125%
OR, put another way:

Fuse rating = (Power/Voltage) x 1.25
OR, put another way:

Fuse rating = (watts/volts) x 1.25

bad_idea

I agree with these guys, use a smaller fuse. The fuse is there to protect the wiring, not the load (lights in this case). Whatever the maximum amp rating a wire can handle safely is what your fuse must be. Otherwise, if there is an issue somewhere (short, malfunction in lights, relay fails, etc) then the wiring will melt before the fuse pops. Been there, done that. Had to rewire a Camaro because of that.

k4ylr

Thanks for the info fellas. The harness is an all-inclusive set up from the shop but I'll look at swapping the fuse out for a smaller one between the battery and relay and getting another in line between the relay and lights.

Now I have to figure out how to epoxy my metal trim clips back on to the a-pillar trim since they broke right hell off.

peligro113

No keep the 30 amp fuse to protect the relay, add a fuse from the relay to the lights.