I posted this over in the electrical section, but thought i might get faster/ more responses here.


So i want to put some Aux back up/ work lights on the underside of my hitch, and then maybe rig up a set to go in a stake pocket to act like a spot light for going to races and derbys, but that part is a different thread. What i am curious about is relays. i get the basic concept of run power to the switch and also to the relay and then the switch tells the relay to send power to the lights... correct? (of course an inline fuse in there somewhere) but i want to know how do i hook up to the relay? all of the relays that i see look like they should be plugged into a fuse box. Does that mean i should somehow run my wires to a fusebox to the leads for a new relay and then plug the relay in?? this kinda has me confused as electrical is by no means my strong point. thanks for any help.


also, where should an inline fuse go in this set up? between the battery and the relay, the batery and the switch, the switch and the relay, or the relay and the lights?

If it matters, the truck info is 97 f150 4.6 4x4 off road xlt and i dont have any lights picked out yet... something for 20 bucks at autozone that i can buy with my points (gotta love free!!)

 

Not sure how many or how powerful of lights you are talking about, but, it seems the simplest way would be a power switch block, with a fuse or auto reset circuit breaker, wired direct to the battery.

Most of the type I'm thinking of, have any number of fused switches, that would be wired with smaller gauge wire, direct to each of your light setups.

I know marine supply houses have them, probably Grainger for sure. They are quite small and could be mounted anywhere that you can conceal wires. Some of them have light up switches as well.

If you aren't related to Tim Allen, this should work pretty well.

Dave

 

To see what I'm talking about, go to www.jamestowndistributors.com. Select electrical switches/panels by BEP. First one should work fine.

Dave

 

You don't need a receptical to plug the relay into. Just use female terminals crimped and/or soldered to the wires you'll use. Then ty-rap the relay in place. A fuse should be placed as close to the power supply feeding #30 'switch' of the relay as possible and also #85 'coil' of the relay.

Here's my favorite site for electrical info; Single Pole Double Throw (SPDT), Single Pole Single Throw (SPST) Automotive Relays

 

thanks for the replies. i Believe that i have found the lights i am going to use. its a set of 20 dollar fog lights from autozone that are 55w each. what does this translate to in terms of what i need for a fuse? i plan on running at least 14 guage wire instead of the supplied 18 because of the length of the run.

a couple of other questions. . .
1. should i run 1 or two power wires the length of the truck, one for each light? or will one wire be fine for both lights?
2, i dont want to wast my battery by accident, so i want to run the switch off of a 12v key wire, and i want to use the one that works my amp and head unit because i plan to install my switch in the opening made by having an aftermarket head unit. is this to much draw for this circut? or will it be ok?

 

and just to clarify, right now, i am only running one set of two lights and one circut to power the set up.

 

is this the type of thing you are reffering too?

Ancor Illuminated Rocker Switch

 

You need to back up a step or so and look at the application in the light of proper sizing and hardware.
First thing is to settle on the max amount of current after you get all the lighting you want.
This determines the size of the main fuse to use as well as the fuse holder and wire size.
Next the fuse must go at the battery so you have the most protection from fire should a short occurr anywhere along the circuit.
Many lights of high brightness take about 55 watts each.
This means 13.6 volts x 4 amps = 55 watts. How many are you going to use at the same time determines the fuse size plus about 10% +/- for long term reliability.
Next the relay control must have contacts rated for the total current plus some spare capacity. Many auto type relays are rated for 20, 30 and 40 amps.
Next, the wire sizes needs to be large enough to carry the total max current draw for the length of the run from the battery to the rear area or voltage drop occurs along with wire heating.
Deside all the lighting you will want then fill in with the proper hardware and sizing.
Look at the use of LED lights where possible to ease the total current draw.
You may even need more than one feed and or branch sub fusing.
Relays are just used to pass high current through so switches do not have to take such high current loads overheat and fail.
For example, backup lighting needs a relay actuated by a tap off the regular backup lights to pass seperate power from a fused source at the battery. Relay 'coils' take little current.
As a former racer, we all use small gas generators of about 1200 watts or larger and be done with it and no wireing hassles.
Good luck.

 

hey bluegrass, thanks for the post. right now all i want to do, is to run a total of two lights at 55w each. (the other lights if they happen at all will be on a completely separat set up, not connected to this one)

so from this posting and the posting over in electronics i have gathered this information

1. stick a fuse as close to the battery as possible for maximum protection
2. use a relay to protect the switch (i kinda already had a feeling it was because switches aren't rated for high output)
3.all the switch really does is open and close the circut going through the relay from the battery to the lights.
4. the relay must be heavy enough (high enough amps) to not destroy itself from lots of current for prolonged periods of time
5. increas the thickness of the wire (smaller number) because of the length (the longer the run = more resitance= more heat= less power at the lights= greater chance of meltdown) and the heavier wire helps to fight this


With this knowledge i feel reasonably confident, i just need help filling in numbers. i seem to see a norm for this setup of a 30a relay, but i am unsure of the proper fuse size. Should i go with what comes with the lights, or should i use my own? also should i fuse the switch as well? and how big of a fuse would i need for this part? also, i have seen a similar project done with 14 gage wire (55w lights and they were run the length of the truck) is that heavy enough, or should i go down to 12?

Thanks i really apriciat the help

 

The current rateing of the relay is not critical as long as it is well over the max you need. Auto 30 amp is fine.
Mount the relay at the rear near the light area. Try to find a location that is protected from constant water splash off the tires.
I would use #12 wire.
Use the larger spade lug type fuse holder with rubber cap off the battery with a 10 amp fuse for 2 55 watt lamps.
The switch need only be half to 1 amp rateing to operate the relay winding.
Secure the wires with good ties so they are not being pulled on and from exhaust heat.
Do good grounds at the lights. Use good quality connectors and workmanship.
Hint: connect one side of the relay winding to the heavey feed then run only 'one' lead to the switch. From the switch run a lead to a nearby ground. This will complete the path to operate the relay once you operate the switch closing ground back to the relay.
My rocker switch is in the fuse panel cover making it easy to get at and work on and operate from the driver location.
Then if the fuse should blow, nothing works and you are fully protected.
Makes life a bit simpler.
Good luck.

 

so if i run it like you suggest i will end up with two wires running the length of the truck correct? both to the relay one from the battery and one from the switch. i am curious as to why you say to put the relay close to the rear near the lights? i am assuming safety? and also im not sure if there is such a thing on my truck as safe from water or mud.. Maybe inside a frame rail near the spare and then wrapped with electrical tape? this truck is not just a pavement pounder, but also a work truck, so things like snow, mud, gravel, and when it rains lots of water get thrown around down there. it almost makes me wonder if these lights would even be safe from shorting out down there.

 

Farmer, I see Bluegrass knows what he is talking about.

The mention of quality connectors and good workmanship is essential. Since the connections will be in the weather, suggest soldering the crimps with heatshrink to assure a mostly corrosion free connection. Over time corrosion and loose connections will be your worst enemy.

 

Good point i am no stranger to the soldering gun, but i will have to make sure to invest in some more shrink wrap. I also am going to try as best i can to limit my total number of connections.

 

The relay dosen't have to go in the rear.
The switch lead becomes shorter and only needs to be #16 wire size.
.
My install was for two backup lights auto actuated from the regular backup light circuit so the relay was placed near the lights.
The spare lights were for towing a large trailer at night and backing up so I could see at the sides.
I have aux front lights set up with the same type relay circuit.
They are setup to offer stock lights or aux at the operation of the switch.
The relay switches feeds between the stock running lights and Fogs.