Relay and Switch Box Install - : Jeep Wrangler JK Forum
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post #1 of 1 Old 04-24-2010, 12:43 PM Thread Starter
Berlin's Avatar
Join Date: Jan 2009
Location: Rockledge, FL
Age: 46
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Relay and Switch Box Install

I know there have been others of these that have done but thought I would share mine. This is very much SPOD inspired as you can tell from the placement of the items in the jeep.

Tools: Wire terminal crimp tool, wire stripper and cutter, solder station (optional), dremmel tool, drill

Durakool 40/60 amp SPDT relays (DG85B-8011-76-1012-DR),
Relay sockets (DZ85AB-5-WH2),
Contra II Rocker switches (V6D2GHNB-AAC00-000),
Enclosure 3.5" x 3.5"x 6.3" including feet needed for mounting (1554K2GYSL),
Radio Shack project enclosure (5 x 2.5 x 2),
1/2 inch grommets,
L brackets for mounting,
7ft 3/8 in flex tube used for running fan wires and switch wires) from Lowe's,
5ft 1in flex tube (for battery cable) from Lowe's,
Many male and female Red, Blue, and Yellow disconnect terminals,
16-18 AWG Wire(red and black, if using relay sockets) for coil,
10-12 AWG Wire(2 or 3 different colors) for load,
22 gauge (again, 2 or 3 different colors) for switch box,
white and black electrical tape
Red and Black Battery cable (6ft)
Screw down terminal (made by Marathon, but I am going to replace)
250 amp Fuse and holder (FPC2G)
Fuse Holders and Fuses (as needed)

I bought some of the harder to find items from I typically tried to go for stuff that was on sale if it worked for me. Some from Lowe's and then the hobby box from Radio Shack. Probably around $150 for what I spent on it.

Relay Notes: I bought SPDT relays, so they have the Normally Closed contact (contact 87a). This worked out well for my initial purpose, a fan cut-off. Also note that they have a suppression diode built in across the coils. If you don't have relays with the diodes, you need them across your coil (contacts 85,86). One other thing, be sure to look at the data sheet on your relays, mine had the polarity of the coil reversed compared to what I have seen in the past!

The Relay Box

1. Decide how you are mounting the relays in the enclosure. Remember to leave enough room for the wires to run out. Drill holes to mount them.
2. If using seperate relay mounts, make sure you have the correct terminals (they are special). Crimp them to wire and feed them into the relay socket. There will be 3 power wires (10-12 AWG) and then 2 control lines (16-18 AWG). There is a special tool needed for this, be sure you know what you are doing if you go this route, I borrowed from work to get it done this way.
2a. If connecting straight to the relay, using insulated female disconnect crimp terminals (the kind you find at Radio Shack or Lowe's) and then crimp to the wires.
3. Drill holes in the box where you wish to run wires through. I used 1/2 inch diameter holes and grommets for these. This worked out fine for the control wires on one side and 2 load wires on the other but I will need to drill out more as I add more stuff.
4. Mount relays with wires connected and run the other wire ends out the holes you drilled. I didn't run them all out right away, just the ones I needed. If using a fuse for your application, cut the wire short, crimp a disconnect to both the wire and fuse holder wire and connect them. Then run another wire out the relay box from the fuse holder and crimp a disconnect to it.
5. Now is a good time to label what you have done. I used different color electrical tape for marking each wire (85,86,30,87,87a) and then put this in an excel spreadsheet that I can go back to.
6. Crimp on disconnects to the other end of the wires.
7. Attach the feet (seperate item for the enclosure I got) to the bottom of the relay box.
8. To mount the relay box in the engine bay, I got a couple of L brackets from Lowes and cut them to size to use on existing screws as shown in pictures below. Test fit and determine how you are going to mount the relay box to the brackets. Drill holes in the brackets to fit.
9. Mount relay box to the brackets.

Close Up of where it mounted.

The Switch box

1. The Radio Shack enclosure I got has a aluminum lid that can be bent. This was useful for getting a template for the curve of the windsheild header in the jeep cabin. One thing to keep in mind is the angle you want the switches to sit at. Use the template to mark the curve to cut on the box. See pic below.

2. Cut a hole in the bottom of the box to fit the switches you bought. One thing I wish I had done here was to have seperate openings for each switch instead of one big one, which means I might have needed a longer box to do it right. What I ended up needing to do was glue the switches down to keep them from moving. This worked fine.
3. Cut the curve for fitting to the windsheild header using a dremmel or similiar tool.
4. Test fit the box against the header and determine where to drill the holes in the header. Once again, the lid can be helpful.
5. Remove the windsheild header (it just pops out IIRC) and drill holes in the windsheild header.
6. Insert switches into box.
7. Cut wire needed. The wire is run from the center of the header across to the drivers side, then down into the compartment by the driver and through the firewall about halfway down the engine bay. Make sure you have enough slack. I needed 9 wires (2 per switch and 1 common to all, I used 3 position switches).
8. Attach wires to switches using female disconnects or by soldering.
9. Attach switch box to header using screws that came with the box.
10. Partially attach header back.
11. Run wires by loop along the center and then along the windsheild header. Push down along drivers side and then push wires through to engine bay using a coat hanger or something similiar.

12. Push the header back in fully. Here's what it looks like.

13. Run wires down to where the box will sit and cut to size. Make sure you have wires labeled. Wrap flex tube around the wires in the engine

Put it together

1. Attach terminal block close to relay box. I used velco along with a tie strap. I'm going to do something else for this, just haven't decided and I was able to get this one from work.
2. The battery cable I used had lugs on both sides. Cut the lugs of off one end and cover with electrical tape. Then run it along the back of the engine bay from the battery to the terminal block. Run the 12V cable through the 250 amp fuse. Don't connect lugs to battery yet (or take
fuse out of holder).
3. Wrap cable with flextube from battery to the terminal block and tie down and secure flextube.
4. Take electrical tape off wire and cut both to size so that they will fit in terminal block. Strip about 1/2 inch off cover of each wire and then insert them in terminal block. Connect lugs to battery.
5. Now take the common wire from the switch box and connect to 12V side of the terminal block after stripping the wire. Connect desired positive relay coil wires to switch wires. Connect negetive relay coil wires to ground. (You can choose to use ground for switch common and then use negetive relay coils for switch wires and connect positive relay coils to 12V)

Here's a pic of how I ran the fan wires back towards the box for my cut off. The wire to the fan goes to relay connection 30, with the other wire coming back going to relay connection 87a. When the coil is engaged it will switch to connection 87 thus turning off the fan.

Final Pic of Cabin and engine bay.

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