Auto wiring questions

[OdiN]

Alright....I have some stuff I need to wire up. I'm good with electronics - I can solder and run wires and all that sort of stuff. I have just not done much with auto eletrical so I'm not familiar with how to properly do things, so maybe some of you can help.

I'm working on a light bar for my Xterra.

The lights came as a set 2 boxes of 2 lights. There is a relay included.

To wire these up - what am I going to need to do?

I want to run all 4 off of a single switch. I believe the included relay should handle all 4 as it's a 40A relay, and these are 55W lights. Ohms law puts that at about 4.5A per light, total well under 40A (Assuming 12V, could be a bit higher, but should be enough room to work with). Then I run power from the battery to the relay and from there to the lights. and from the relay to a switch on the dash? I don't know what each position on the relay is for.

Also - can I just use one positive and one negative wire and have all of the lights connect into that single line?

I'm assuming it's similar to a computer as it's DC power.

The lights came with a wiring harness that the relay plugs into on the end. It does have a fuse in-line on the power wire. However, it's only a 15A fuse. The other thing is it wants me to hook these up with the actual headlights - I don't want to do that as I want them on a seperate switch, and this part is what confuses me about what does what on the relay.

Also the wire looks to be 14 gauge which I'm not sure is enough for all of the lights.

Any tips? I guess mainly it's getting the switch and relay to work how I want.

 

[franksta]

If you do run a single power and ground wire just make sure they can handle the total current load.

I never understood the weird post numberings on the relays I've seen so I went without. Fused link to the battery --> switch under the dash --> lights --> ground, has been working fine for me for 7 years or so. I think the relay is the better (safer) way to go if you can figure it out.

 

[Zenmervolt]

Answers to your relay questions:

http://www.bcae1.com/relays.htm

ZV

 

[OdiN]

Originally posted by: franksta
If you do run a single power and ground wire just make sure they can handle the total current load.

I never understood the weird post numberings on the relays I've seen so I went without. Fused link to the battery --> switch under the dash --> lights --> ground, has been working fine for me for 7 years or so. I think the relay is the better (safer) way to go if you can figure it out.

Well the wires will be running 4 lights, each light is 55W (12-14V from battery) so that puts it at 18-22A. I'm not sure if 14 gauge is okay or if I should go to 12 gauge wire.

I want to keep the lines running power to the lights from running up around the dash electronics. That and the in-dash switch isn't built to run that much power through it.

 

[bruceb]

Odin, if that is a standard bosch auto plug in type relay (1/4" male tabs on it)
then here is the hookup:

Relay Coil is on Terminals #85 & #86 .. either one can go to the chassis Ground of the car

Relay Contact Common: Terminal #30

Relay Contact Normally Closed: Terminal #87A (when the coil is Not Operated)

Relay Contact Normally Open: Terminal #87

Basically you want the High Current from the Battery to go to Terminal #30
and a wire from Terminal #87 goes to the Fog Lamps

You will wire a switch such that it provides +12V to the coil on the terminal you
did not use for the coil ground. The supply for the switch can be from almost
anywhere in the car, but a good method is to tie into the Parking or Dash Lamps
circuits. That way, the fog lamps can not be on without the taillamps being on which
is a law in some states. Do not forget to fuse the wire from the Battery to the relay.
And I would suggest 12 Ga wire which should be more than enough for 4 55W lamps.

 

[OdiN]

Ok so here is what I am getting:

#85 -> Chassis Ground

Battery -> Fuse -> #30

#87 -> Positive to Lights

Battery -> Fuse -> In-Dash Switch

In-Dash Switch -> #86

In-Dash Switch -> Chassis Ground

Ground on Lights -> Chassis Ground

These aren't fog lights so they need to be on a completely separate circuit. They are off-road lights and are illegal to be used on roads with normal traffic.

So does this look right?

What rating of fuses should I use?

For the battery to switch a small one should work, right? 2A?

 

[Colt45]

Originally posted by: OdiN
Ok so here is what I am getting:

#85 -> Chassis Ground

Battery -> Fuse -> #30 - 10GA

#87 -> Positive to Lights 10GA

ign switch -> Fuse -> In-Dash Switch --- if you want it to kill the lights with the car off, otherwise battery..

In-Dash Switch -> #86

//In-Dash Switch -> Chassis Ground ---- only if switch is illuminated

Ground on Lights -> Chassis Ground - 10GA

These aren't fog lights so they need to be on a completely separate circuit. They are off-road lights and are illegal to be used on roads with normal traffic.

So does this look right?

What rating of fuses should I use?

For the battery to switch a small one should work, right? 2A?

Yeah, 1A is plenty for the switch, go 30A for the bulbs... 40 if it pops.

 

[OdiN]

I want the switch to operate the lights at any time - whether the car is on or off. So I don't want to do anything with the ignition switch.

Oh and yeah the switch has a light on it.

 

[bruceb]

Switch to the relay only needs a 1 AMP fuse .. maybe less as relay coils
do not pull a lot of current. If you have a Lamp in the switch then there are
a few possibilities

1): The lamp is partially wired internally in the switch... If so the not connected
lead of the lamp goes to Ground and the other terminal (which would have the
lamp & one switch terminal) would go to the relay. The switch terminal all by
itself would go the +12V source

2): The lamp is completely seperate within the switch, wiring wise. In that case
run a Ground to one Lamp lead and connect the other Lamp lead to the wire going
to the Relay.

For fuses, use a 20AMP on the main wire from the Battery to relay .. This is calculated
at 55W running at 11VDC, which it will drop to, if the car is not running .. so 5AMPS per Lamp = 20AMP
You can also add 4 5AMP fuses one to each lamp for extra protection. That will also keep other lamps
working if one them causes a short.

 

[Colt45]

Originally posted by: bruceb


For fuses, use a 20AMP on the main wire from the Battery to relay .. This is calculated
at 55W running at 11VDC, which it will drop to, if the car is not running .. so 5AMPS per Lamp = 20AMP
You can also add 4 5AMP fuses one to each lamp for extra protection. That will also keep other lamps
working if one them causes a short.

20A with the bulbs hot! They'll pull a lot more on turn-on, and it will probably pop a 20A fuse unless it's a slow-blow. So I think 30A is more reasonable.

 

[bruceb]

30Amp is probably overkill .. Try it with 20A and see if it pops ... likely not
as that was calculated at 55W at 11V = 5A per lamp .. at 12V it becomes 4.5A
and if the car is running, even less. So at most, a 25A fuse would do.