This is not a project that you want to do when you’re crunched for time. I would budget an entire weekend. It took me a little longer because I chose to use a Dremel tool. While this is far from the fastest tool, it is very easy to control and gives you a very clean cut. Another time eater is the application of the Herculiner. To properly apply it, there is a lot of prep work then time to allow for drying between coats.

What you’ll need:

• Misc. Sockets
• Dremel
• Heavy Duty Reinforced Cutoff Wheel for Dremel
• Sander & Sandpaper
• Rivet Gun & Rivets
• Sharp Knife / Box Cutter
• Heavy \ Thick Gloves
• Eye Protection
• Face Shield
• Breather Mask
• Painter’s Tape
• Herculiner Kit
• Disposable Gloves
• Heavy Duty Zip-Ties
• Kids Play Toy Chair Optional

NOTE – You can substitute your favorite cutting tool in place of the Dremel

Before I started, I took a few pictures and modified them to play around with different configurations and make doubly sure I wanted to go through with this. Here are the pictures I modified in GIMP for testing:

stock – flares attached:

flares removed:

fenders trimmed:

flares trimmed and remounted:

OK, I like that, so it’s time to get down to business. I waited until I went home to visit my family to do this. They have a driveway and plenty of room to work and spread stuff out.

Remove anything that will be in our way. This includes the flares, plastic trim, and rockrails (because I’m Herc’ing the bottom fenders)

Position the flare where you want it. I did this to make sure where I had already planned to trim will work with the flare placement. If you look at the rear/bottom of the flare, you can see where I trimmed off the curved piece so it will sit flush for the mockup. Here is also where I found out that painter’s tape is the way to go. The regular masking tape left glue residue and pulled the paint off of my flares. The painter’s tape did not. It’s well worth the few extra pennies.

Take a very deep breath and/or a swig if your favorite beer, put on your eye/face/ear and hand protection and cut away. As you can see, it was easy to mark where to cut because I cut right where the fender does it first flare out.

If you are going to use a Dremel like I did, here are a few tips. First, get the heavy duty reinforced cutoff disks. I used about 1.5 disks per fender. Having them reinforced makes them last longer and if they do blow up on you, the reinforcing backing keeps them out of your face. Another trick is to not put much pressure on the material you are cutting. Score your cut line about 5 or 6 inches long to give you a good guide. Then slowly and lightly go back and forth over the same 5 or 6 inches until you are through. If you see black/brown smoke/dust, you’re pushing too hard and that dust is the wasted cutting disk you’re burning up.

Here’s another spot where the painter’s tape will help. It will help keep you from burning your good paint. The cutting tool will throw off a lot of sparks. If left unprotected, these sparks will mar your paint.

I ran into a small issue with the front fender. My first line wasn’t going to work.

This whould leave the sheet metal too close to the tires. So I rethought my line and recut it like this. Cutting it this way eliminates one of the fender mounting bolts, but I have yet to run into any issues. I kept the bolt just in case I need to use it.

Time to mark for the new flare mounting holes. I held the flare up to the fender. Then marked the first and last hole. Then put the flare back off to the side and held up the freshly trimmed fender up to it, lined up the first and last holes and marked the remaining holes. You will not use all of the original holes. A few are lost because of the spacing.

Temporarily remount the flare

Using more tape and an angle finder, I measured out a 30 degree line from the bottom outside edge of the fare upwards. The tape was marked with arrows on the cutting side just to make sure I didn’t do anything stupid:

The rear of the front flare was done in a similar fashion.

The flares are easily cut using a Dremel or even a sharp box cutter (pictures further down with finished pictures)
Now onto the rear…

Because the rear fenders have pinch seam welds that shouldn’t be cut out, I first trimmed up to the welds:

Then cut slits in between the welds. Followed that by laying a large bead of RTV behind the fender so it would seal up the crease created when I beat in the fender. You will also see I only cut and folded the front and back of the fender. I left the top alone because I wanted to remount my flare:

NOTE: you can also see that I redrilled the mounting holes up fractions of an inch higher. I would suggest against doing this. There isn’t enough extra clearance gained by doing this. Now when I permanently remove my flares and finish folding the top in, I’ll have to fill the holes in with weld to reseal them.

Now bolt the flares back into place. I decided to use heavy duty zip-ties instead. They are strong enough so far and are a lot easier to work with.

What you’ll need:

• Project Enclosure 8″ x 6″ x 3″ from RadioShack (model number is 270-1809)
• Drill with assorted drill bits
• Something to cut the plastic box with (rotary tool, box cutters, band/hack saw, etc)
• Ruler
• Metal Snips
• Rivet Gun & Rivets
• Metal File
• Clamps

Here’s the project box new from RadioShack

It comes with a lid, screws to hold the lid down, and a metal board/shelf. Keep the metal board because it will be used to make the wings that go under your sun visor clips. The lid won’t be used in this writeup.

I chose to make the box as large as possible. So the face will be the full 3″ tall. The back will be 1″ tall. The sides will be cut straight to intersect at the ends. I chose to make a mockup out of poster board just to make sure before I cut into the box. I’d suggest you do it as well to make sure you like the size and that it fits with your application.

I could have changed up the design a bit and cut it something like this:

or

One thing to remember – the height of the back face dictates the angle of the front face. Make the back shorter, and it will angle the front down more (like in the second alternative I showed above). Just make sure if you do this, that it won’t cause interference with the headliner and your switches/wiring.

OK, so now go out and check how your model fits:

I lucked out in two ways…

1. With a 3″ tall front and 1″ tall back, the bottom of the box is perfectly horizontal. I didn’t plan this, it was sheer luck!
2. The model shows that the straight cuts on the sides won’t have to be modified. It stays tucked up the the headliner nicely. If you place yours farther forwards or back, you might have to contour the sides to match your headliner.

You can also see how far out the box will be. For some with overhead consoles or the overhead IR keyless entry system, you might have to modify the deepness of the box like I demonstrated a few pictures up.

Alright, now to cut up the box. Transfer your dimensions/measurements on to the box:

Now cut it out

Because my Dremel has been taking a beating recently and the fact that it’s sound has probably been pissing off my neighbors (apt living), I wanted to try to cut it with something less noisy. And wanted to show people without special tools and workshop can also do it. Heck, I did this in my living room floor in my apt. So I tried a sharp box cutter. If you do this, BE CAREFUL. The cutter likes to slip away from you and try to chop off digits. I’d wear thick leather gloves and be super slow. It takes a few extra minutes, but it produces a sweet and clean cut…

While cutting it, I had a thick metal ruler clamped to the box to help me keep a nice straight line.

But then I just wanted the darn thing cut, so I cut the sides with my Dremel. But because it’s on the fritz, it will only run when set to 10,000 rpms. And at that speed, you don’t cut the plastic, it melts it.

No worries. I few minutes with a metal file cleans it right up.

Now go outside and test fit it…

Fits perfect!

So now we need to start figuring out how to keep the box up there. So we need to make wings to bolt up under the sunvisor clips. I took a scrap piece of poster board and slapped it up there. Then placed the box in its final position and traced the outline of the box and the clips:

Now we have a somwhat accurate representation of the layout that we can take inside with us.

We find out that the screw holes that hold the clips on are 9″ apart on center. And that the outter edge of the clips are 10″ apart. This will let us know how wide our wings need to be.

So if you do your math, the clips stick out approx 1″ from the sides of the box (10″ wide measurement on the clips minus the box that’s 8″ wide and divide by 2). So just to be safe, I made my wings 1.5″ wide. I chose a depth of 3″ to give it a good solid base and a good area for attaching the wings to the box.

Once you figure out the size of your wings, you need to see how far down you need to make the wings to into the box. Take your measurements, and that will give you those dimensions. I would make the inside edges a little shorter than they measure out so they don’t bottom out on you and keep the bend from sitting flush on the box.

I used that mockup piece to test fit it to the box to see if I had any bottoming out issues. Now transfer the completed dimensions onto the piece of metal that came with the box. I highlighted the lines because my original pencil lines didn’t show up well in the photo. Also, the middle line isn’t a cut line, but a bend line.

Get out some metal sheers and cut out two of them:

Because the metal is somewhat soft (I think it’s aluminum), it will be easy to cut and bend.

Speaking of bending, time to bend up the wings:

I didn’t use any jigs or bending tools for this. I simply layed them on the edge of my desk one at a time and bent them over the edge. MAKE SURE YOU BEND THEM CORRECTLY, YOU DON’T WANT TO END UP WITH TWO DRIVERS SIDE WINGS And once they are bent, it’s a good idea to mark them D for driver’s side and P for passenger’s side.

Now that they are bent up, it’s time to drill the holes/slots for the visor clips. But you don’t simply measure 1/2″ from the bend and mark your center line. You have to account for the thickness of the wall of the box because the wing will attach to the INSIDE of the box.

So hold the wing up inside the box tightly:

And mark your line

Now you can mark your centerline 1/2″ from that line. (Remember, the box is 8″ wide and the clips are 9″ apart. 9 – 8 = 1. Then divide the 1″ in half for each side to get 1/2″ on each side).

Onto the clip. The underside of the clip looks like:

So we need to account for all of the parts that don’t sit flush with the headliner.

First drill the holes for the two main protrusions:

Then drill some holes inside of those to make a slot:

Use the metal file to clean up the edges up and see if it fits:

Now I kinda missed a few steps here photographically, but I’ll do my best…

It’s now time to attatch your wings to the box. Position the wing where it belongs on the box. And as best as you can, trace on the outside where the wing sits on the inside wall. It doesn’t have to be exact, but close as you can get. This is your boundary for your holes that the rivits will be placed in.

Drill (into just the box) as many holes as you deem appropriate. I went with 3 on each side. Two in the front and 1 in the back. Should be pleanty. Now take your wing and clamp it back into position. Take a pencil and mark your holes. Then unclamp, drill your holes, and then rivit the wing into place. Do this for both sides.

Here’s how mine turned out:

Now cross your fingers and hope your measurements were good and go test fit the box:

Sweeeeeet. But I noticed that the edges of my wings were digging into my headliner more than I cared for:

No biggie. Just trim a little off of each edge:

The old gen II box next to new gen IV box:

You can see how much more room this one will have for the wiring. I like that.

Time to drill some holes for the switches and LEDs. Here’s where I lucked out AGAIN. I am running 7 switches. It just so happens that there are 7 reinforcing ribs that run along the face of the box! Sweet. I only have measure to center them vertically. Drill points marked in silver:

And after some drilling:

TADAAAAaaaaaa!!!

Things to think about…

• This was for a 1998 XJ with no overhead console to worry about. I’m sure other model years that have/do not have overhead consoles need a little tweaking from what I had to do.
• The roof lines might be slightly different.
• Different model years might have different clip designs so you may need to cut your holes in your wings differently
• Different model years might have a different distance between the clips you may need to account for.

After running this setup for a few months, I found my switches that came with the ARB goodies and decided I wanted to use these. And with this box, I would have more than enough room for them. The older versions of the switch boxes weren’t deep enough to use them. So I pulled the box out and made a few cuts: (you can also see the silver Hammered Finish paint I used)

It looked OK but something just didn’t flow right. So I went back and tweaked on the box some more. What I tweaked:

• Recut the box so it was 3″ tall in the front and tapered down to a point in the back instead of a 1″ face in the back.
• Added automotive door trim molding to the top. This really cleaned up the look.
• Used slots in the mounting wings so I could slide it closer to the windshield.
• Modified the mounting of the wings a bit.
• Found a place that sells matching Carling switches that match my ARB switches. They also have mounting panels that really clean up the look of the mounted switches

The modifications to the wings:

Finished product:

The 4 matching switches are made my the same company that ARB purchases theirs from; Carling Technologies. I ordered the extra switches from www.WaytekWire.com. The switches are inserted into mounting panels also made my Carling (also purchased from Waytek Wire. They really clean up the look of the install.
A couple of variants I have made for friends:

The wiring stayed pretty much the same. It has 3 wires coming into the box.

1. Power in for the switches
2. Ground for the switches
3. CAT-5 ethernet cable to connect to the relay box.

So I figured I’d make it in 2 pieces – make the wings separate from the box itself.

After making the 2 side pieces and the 1 main box portion, it would be super easy to rivet together.

This time I waited until I went home to visit the family because my dad has a decent shop setup I could use. It works better than my living room floor

And because I wanted to make the bends as sharp, even, and consistent as I could get them, I made a little bending jig. It was pretty simple to make. It consists of some scrap angle I had laying around and a few hinges. The strip of metal sitting on top gets clamped down to the sheet metal to keep the bend tight. It needs to be just shy of 8″ long so it can fit in between the outter tabs of the box.

OK, time to get to work. With this new design, I found I could make 2 switch boxes out of the same sheet my gen II box would only allow 1 box. Score!

Trace out the design and cut the sheet in 1/2. I stuck with the metal shears to cut the sheet.

Center punch the holes to be drilled then drill them out. I chose to once again drill holes in corners to help the bends come out cleaner:

Finish doing the cuts to create the tabs

Time to bend!

Now those are the bends I like to see! I would like to point out the “tabs” at the top of the front and back face. They are bend as far inward as possible. These bent in tabs greatly increase the rigidity of the front and rear panels.

Time to do the end panels/wings. Trace the pattern out, cut it to shape, and drill out the corners as well as the holes to start the wings mounting strips.

Final bend is MUCH easier now:

Now rivet the end panels to the box:

No, the design is almost exactly the same as my gen II box. But this gen III box accomplished the goal of being able to make them much easier as well as provide a cleaner finished look.

I actually never used this box in my XJ. Before I could paint, wire, and install it, I thought of a much easier way to make a box. Thus giving me my gen IV box.

I started out with the basic measurements from the switch box that I had purchased, and made a few modifications that I wanted in a switch box. So with a pair of scissors and some poster board, I made a few mockups:

After I found the design that gave me the best fit while still giving me the extra space for wiring, I drew up the plans so I could bend it out of a single piece of sheet metal:

Because, at the time of making this version, I lived in an apartment, I decided to rivet the box together over welding it closed.

Picked up a sheet of sheet metal from the local hardware store:

Forgive the next few pictures, but I had my camera on the wrong settings and I didn’t notice this until afterwards.

Trace out the pattern on the sheet:

Drill out the corners of the bends. I found that this keeps the sheet from cracking/tearing and it allows for tighter bends in the corners:

Next I used a pair of metal sheers to cut out the shape then used a rotary tool to cut out the slots in the wings:

Drilled out the 7 holes for the switches:

Then drilled out the holes for the LED indicator lights:

Next I drilled out the holes for the rivits:

I then proceeded to bend up the box. You can see in some of the pictures that I used heat to help the bending along. I was MacGyvering the bends using any hard object that I could clamp to the metal to give me a surface to bend against.

Just like a cooking show.. **POOF** Here was the first test fitting. If you look at the next 2 pictures, you can see why I decided to use slots in the wings. It allows for a little bit of adjustment.

I then did all of the wiring and stuffed it all inside of the box. This setup doesn’t need the cutting of the headliner like my old one did:

And here’s the fully wired, painted, and installed box:

The switches were wired as following:

1. Master power – this needs to be on before any of the other switches will function
2. ARB air pump
3. ARB rear locker
4. ARB front locker
5. Roof rack mounted lights (outside 2)
6. Roof rack mounted lights (inside 2)
7. Bumper mounted fog lights

Here’s a simple wiring diagram of how it was wired

You will notice that I also wired mine up so the lockers couldn’t be engaged unless the pump was engaged. I figured this might help me from accidentally locking the lockers. The writeup for the Relay Box can be found here.

The switches controlled the following:

1. ARB Pump
2. ARB Rear Locker
3. ARB Front Locker
4. Bumper-mounted Fog Lights
5. Roof Rack Lights (outside 2)
6. Roof Rack Lights (inside 2)
7. Not used

The switches controlled the accessories through my relay box.
The only issue I had was with the switches I used. They were rather deep and required me to cut out part of my headliner to get the wiring to fit.

Pics (PLEASE excuse the hack wiring. I’ve since gotten better )

After 2 months of running this setup, I pulled it down to do some tweaking to it. Well when I pushed everything back up into the headliner, I got lucky … in a way. Because of the limited space, one of the signal wires touched the power in terminals, thus cutting on a pair of my roof rack lights. Lucky for me, the battery died before any real damage occurred:

That’s when I decided to go with a different switch box setup. The box I had bought was excellent, I just wanted/needed a little more space. The writeup on the gen II switch box can be found HERE.

What you’ll need:

• Plastic coated cable:

• 8 wire clamps:

• 2 Eye bolts (4″ was a little too long but worked fine):

• 4 snap hooks:

• 2 Extra bolts that fit your eye bolts if needed (you need 2 nuts total on each bolt and my bolts came with a nut each):

NOTE – you don’t have to buy packages of stuff like I did or else you will end up with extra stuff. But I was in Wal-Mart when I remembered to get the parts and Lowe’s was closed so I had to just get the Wal-Mart packages. And no, you won’t use anywhere near 30′ of the wire rope.

Now on to making the cables.

Figure out where you want your eye bolts to attach. Then disconnect your swaybar and push them up out of the way as far as possible. Then guess how much cable you’ll need to make a loop all the way around the swaybar & disco and back to where you want your hook to go. And to just be safe, add about 6-8 inches for error and securing the clips.

On my 98, there were holes already in the fender support bracket that I ended up using:

So far that spot works out well. And it didn’t involve removing the battery or airbox if I had mounted the bolt vertically.

Cut your cables:

Lay out your hardware:

Make your “loop” and secure with your cable clamps:

Repeat on the other side:

Whalla! You now have a nice and easy way to secure your swaybar and disco’s while offroad:

Oh yeah, repeat for the other side of the XJ.

I like having clips on both sides of the cable so I can throw them in the glove box instead of leaving them dangling under there. Especially during winter time. Others have also suggested it might be a little cleaner if the crimp wire holders were used over the clamps. If I ever find the need to remake these, I will probably use them.

The rack is 45″ wide and 60″ long. That size seems to fit the XJ roof nicely if you’re going for, what I consider, a full length roof rack.

The rack came with the “J100″ mounting brackets/bars. The J100 brackets bolt to the rack and clamp onto the factory roof rails. Some people experience problems with this setup when the factory rails separate from roof because of the weak connection between the rails and the roof. I have not had any issue with this setup. I have seen posts on the XJ boards about how Jeep changed the way in which they mounted the rails to the roof around 1997. They said they changed it to a stronger metal mount and went away from a plastic style mount. Surco does make a mounting system that uses the gutter rails rather than the roof rails.

Overall, I’m very pleased with the rack. It’s light-weight enough to were it’s easy for me to take the rack off by myself with little effort. However, it being a light-weight rack comes with some drawbacks. It’s not rated to carry as much weight as some of the other heavier metal racks are rated for. For me, this hasn’t been an issue. I try to keep all of the heavy stuff as low as possible to help with off-camber situations. I keep a shovel, ax, and hi-lift on there with no issues. Occasionally, I put my 32″x11.50″ spare tire up there for around town and long trip driving when I need the extra interior space. I’ve also used it to stand on while taking pictures with no ill effects.

Here are a few pictures from different angles taken the day I bought it:

I found that it really helps to have the factory cross rails under the unsupported ends of the tire. Without them, I found the rack would rattle and wobble when I hit bumps with the tire up top. The previous owner also added a piece of angle across the rack where the tire hits to add a little more extra support:

The original owner didn’t use the Surco light tabs. Instead, he just mounted them directly to the rack, bending the light’s joint 90 degrees so they pointed up. This worked, but didn’t allow me to fine tune the pointing direction left to right. But I sure as heck didn’t want to pay what Surco wanted for light tabs. Here’s my cheap fix:

Light Mount/Tabs

I went out to Lowe’s and picked up a 3′ stick of angle that had predrilled holes throughout it. Then bolted it to the front of the rack using the holes that were used originally to mount up each light:

I do not have any closeup pictures of the lights mounted, but they’re simply bolted down to the flat part of the angled metal. I really liked this mount because all of the predrilled holes allowed me to move the lights around with different spacing. It was also painted with Rust-Oleum Hammered Finish before the final install.
I also was too cheap to pay the high dollar price Surco wanted for the other accessory mounts, so I went about making my own as well. It wasn’t the cleanest solution, but I used materials I had laying around and they’ve worked great so far.

Shovel / Ax Mount:

I had a few small sections of angled metal that had predrilled holes that I decided would work for what I needed. The only difference between this angle and the angle used for my light bar was that these sections had holes/ovals that alternated orientation. But it still worked just fine.

Here are the angle brackets bolted to the rear side of the rack:

Same design/setup for the front:

Now for the shovel and ax. I simply used two small u-bolts from Lowe’s to secure them together. The wing nuts allow them to be taken apart without needing tools:

Then simply use a set of larger u-bolts to attach the ax to the rack mounts:

Hi-Lift Mount:

I basically mimicked the ax/shovel mount on the other side for my Hi-Lift mount:

(the rack was rotated from the above pictures so I could work on the other side)

Side-By-Side Comparison

Airflow on top, ARB on bottom:

Airflow on left, ARB on right:

Airflow on top, ARB on bottom:

Airflow on left, ARB on right:

Mounted / Installed pictures:

You can see how the Airflow snorkel does not interfere with the raised fender flares:

You can see how far down the ARB snorkel comes down on the body line here:

The other major difference is how each snorkel enters the engine bay. The Airflow snorkel runs directly into the engine bay near the brake booster, directly where the ABS equipment is/should be. This is why the Airflow is advertised to only work with NON-ABS equipped XJs. The ARB snorkel enters the outer fender skin and turns 90 degrees towards the front of the vehicle. It then loops down under the factory airbox and enters the engine bay there. This is why the 97 and newer XJs will require the removal of the washer fluid bottle.

I chose to mount my relay box in the back cargo area for two reasons.

1. I couldn’t find a place in the engine bay that would hold the box (I wanted the relays in a box to help shield them from the elements).
2. I already had a nice large-gauge wire run to the cargo area to power my amp (that got stolen months ago grrrrrrrrrrr).

Here is the hobby box I picked up from RadioShack. The two strips you see on the bottom are the fuzzy side of velcro. I wanted all of the contents of the box to stay firmly in place but I didn’t want anything too permanent. So I tried out the velcro.

Here is the power distribution block/fuse box I used to power the relays. I picked it up from Advanced Auto for a few bucks:

This is how I laid out the box. Everything is velcroed down. Unfortunately, because the relays aren’t very big and will get pulled from the tight wiring, using just velcro wouldn’t do. I’ll show you how I fixed this later. You’ll also notice that the fuse box only holds 6 terminals and I have 7 switches to run. So I picked up one of those inline fuse holders and attached it to the stud that attaches to the incoming power wire.

I then ran the power leads from the fuse block to the relays. I also went ahead and ran my daisy-chained ground wire to each. You can also see the above mentioned 7th fuse holder attached.

This is how I resolved my lose relay situation. I had a small piece of narrow aluminum flat stock laying around. Bent up the ends and later drilled holes to bolt it to the box. Now those relays aren’t going anywhere.

And much to my luck, the stock fit nicely in between the reinforcing ribs in the hobby box!

Brace yourself, but here is a picture of everything hackishly installed. I did all of the stuff up to this point a few weeks back and was very rushed. So I apologize…

I needed it in and running for an offroad trip. I didn’t even have time to bolt it to anything, install my relay retaining aluminum strap, or anything else. I also jerry-rigged the connection from the 4-guage wire to the fuse block. VERY HACKISHLY I might add.

In a weird coincidence, when I went to Wal-Mart to fill my prescriptions for pain meds after I separated my shoulder, I found these nice terminal connections that would solve my issue of how to connect that large-gauge wire to the fuse block terminal.

Butta! (this pic was just for demonstration of fitmant – I crimped and heat shrunk before installation)

Time to install the aluminum relay retainer:

Time to think about how to mount this up:

If you’re wondering why I put a nut and washer on before the box, it’s because I wanted to be able to remove the box without having to remove the interior panel.

After I did that, I took everything out of the hobby box and neatened and tidied everything up. I also drilled holes in the side of the box and installed grommets to run the wires through.

And here’s the finished result:

This is how I ran my wires to/from the box. In my ‘98, the panel has 6 rectangles cut in it (almost looks like for ventilation). Lucked out again. One less hole to cut.

Repacked everything back up and good to go!

This setup has worked well for all of my switch setups without needing to be modified at all. It has worked out flawlessly. I have plans though to replace it with a new setup. Since this project, my wiring skills have gotten better and I have a few more ideas of what I would like to do. There will be a full writeup on that when it gets completed.

Terminals 85 and 86 form the coil contacts. As current is passed through the coil, a magnetic field is produced, which actuates the switch contacts, causing terminals 30 and 87 to close. It is sometimes argued as to which terminal (85 or 86) should recieve the ground 12-volt power source. For the purpose of this writeup, all diagrams are labed with the signal current connected to the 85 terminal and the 86 terminal going to ground. It is recommended that you check the diagram that is printed on your specific relay.

There are a handfull of different relays out there. But for this writeup, I’ll only be concentrating on the three main types.

Single Pole Single Throw (SPST) Relay

This is the most simple relay used in most automotive applications. SPST relays have only 4 terminals (30, 85, 86, 87). When the relay is switched off, the coil is not energized. This allows a spring to pull the internal switch away from terminal 87, thus stopping the flow of current. When the relay is switched on, 12 volts pass between terminals 85 and 86 causing the coil to become energized. When the coil is energized, it becomes a magnet. This pulls on the internal switch and causes it to make contact with terminal 87, allowing current to pass through the relay and to your device you are powering.

(in the following diagram, the yellow line is fictional and is only there to represent the internal connections of the relay)

Single Pole Single Throw (SPST) Relay (with double outputs)

This relay is almost exactly like the standard SPST relay with a single output. Only this version has two output terminals. These relays have 5 terminals (30, 85, 86, 87, 87A). When the relay is switched off, the coil is not energized. This allows a spring to pull the internal switch away from terminal 87, thus stopping the flow of current. When the relay is switched on, 12 volts pass between terminals 85 and 86 causing the coil to become energized. When the coil is energized, it becomes a magnet. This pulls on the internal switch and causes it to make contact with terminal 87 and 87A, allowing current to pass through the relay and to your devices you are powering.

(in the following diagram, the yellow line is fictional and is only there to represent the internal connections of the relay)

Single Pole Double Throw (SPDT) Relay

These relays have 5 terminals (30, 85, 86, 87, 87A). When the relay is switched off, the coil is not energized. This allows a spring to pull the internal switch away from terminal 87 and onto terminal 87A, thus sending power to the 87A terminal. When the relay is switched on, 12 volts pass between terminals 85 and 86 causing the coil to become energized. When the coil is energized, it becomes a magnet. This pulls on the internal switch and causes it to make contact with terminal 87 and away from 87A. Now terminal 87 is receiving the power while 87A no longer does.

(in the following diagram, the yellow line is fictional and is only there to represent the internal connections of the relay)

Relay Links:

• the12volt.com
• wikipedia