Using your existing relay box for adding electric accessories

Chris

Administrator
Staff Member
Ride of the Month Winner
Joined
Sep 28, 2015
Messages
70,949
Location
Florence, AZ
This write-up was performed on an XJ, but the concept (and a lot of the diagrams) should be very similar to a TJ.

The motive is to use the existing fuse holder and existing relay holders in the Power Distribution Center (PDC).

I got no ABS, so the whole top row (as shown on the diagram) is empty in mine.

There's also plenty of fuse spaces.

Go get a PDC at the junkyard that matches yours.

Relays are gone but the boxes are everywhere.

36838d1297028118t-pdc-voltage-leak-killing-battery-need-fuse-identification-help-plz-xj605940.jpg


Remove your positive terminal from the battery, and the feed to the PDC from it's main terminal.
There's 2 metal tabs to remove the PDC from the body (big screwdriver)
Then 6 tabs to remove the bottom cover.
That's all that's in mine, if you got a lot of options, power windows, power doors, all that, you probably are a little fuller in there.

23ada4fd.jpg


7a1a5039.jpg


32f279e4.jpg


Remove the cover from the bottom of the bus.
These are things you should start doing first on your junkyard PDC, so you get used to breaking the little tabs off, and realizing how you should have removed it without doing that.

97072c81.jpg


So looking down through the main fuse bar, you can see the empty holes have no metal terminal in them, you need to get the little connectors out of the JY PDC and put them in yours.
I should have taken the other fuses out for this pic so you can see what I mean.
Take a picture of your fuses & relays so you know where to put them back...

3e0856f7.jpg


This is the JY box, the bus (the main terminal in the PDC) has been removed. It's just plugged into every slot, so work it with a screwdriver out of there.

3217b7bc.jpg


Remove the bus plugs, the little metal inserts.
There's little slots in the front that catches a tab on the metal part, then it slides right out the bottom.
The first one isn't coming out easy, but start cutting the junkyard box open if you have to and when you get the first one out look at the little catch on the side of the bus plug. You have to hit that from the front, through the slot in the main housing.
Plug them up from the bottom, into your PDC.

b024e9e0.jpg


In both pictures I have the yellow fuse center plate in, but that has to come out to do all this, and if you break any of the little tabs, the yellow thing isn't going back in right.
So don't do that.

Also, look at the bus and the last fuse spot at the main terminal, where it plugs in is the opposite side, so consider that when you're putting your bus plugs in.

d5d923be.jpg


You need to get a good bit of the wiring pigtail when you get your junkyard box to reuse the wiring & connectors.
By now you've shredded your JY PDC.

b9d732f6.jpg


Plug those into the bottom of yours.
There's different wire sizes, pay attention to that for what size relays you're going to use, which you would figure out using the first chart.
I was able to add 3 new fused hot leads, and will be taking them straight to a new relay bank.

f389c6c6.jpg


Each row is independant of the box, and again with the little tabs that break super easy.
The yellow part comes off first, 2 tabs from the bottom.
Then the black part pushes through the bottom, with 2 tabs on each side of the top.
So I ditched the 2 large relay spots, for a row of the (4) 30a ones [4671168].
There's a little nub I had to chop off so the 4 bank fit where the 2 one was.

84a07078.jpg


5a5f9163.jpg


So since everything hot is right there, I'll do a ground trigger.

relay_diagram_01.gif


The 3 new hot leads are the 30s, tie each 85 to that to power the switch.

38c1afcb.jpg


The yellow/brown/green are my 3 86s to the cabin, the big reds are my 87's.
I'm only using 1 for now, to do my driving lights, the other 2 are for future.

fdea8a14.jpg


57eee8c8.jpg


So here's the new arrangement. New bank of 4 across the top. Only 3 of those are wired up, only 1 of those is in use.

3a920a35.jpg


All I have to do is plug in fuses & relays, and these two are 30A feeds.

da847d37.jpg


I also made an extra 60A fused lead with no relay, for a future inside relay box.
It's not hot until I plug a fuse in that last position.

c9a6d489.jpg


Testing out my switch at the battery.
The brown is the one I'm using, the yellow and green will switch the future relays.

76104575.jpg


And finally...

22e0c7e0.jpg
 
This site contains affiliate links for which Jeep Wrangler TJ Forum may be compensated.
Hey - thanks for this write-up. Yesterday I was having a weird problem with my TJ, and in the process I opened up my fuse box and noticed the end was "empty" where some relays (for things my Jeep doesn't have) were supposed to go. I'm gunna now have to look for one of the quad-relay holders (well, the whole box and harness) to slot in there in the future. I've got some LED pods that came with her that were wired up very improperly: Wired direct from the battery (no fuses), thru a small hole in the firewall (no grommet!) to the switches (no relays!). It was a fire waiting to happen, and once I noticed it, I unplugged it post-haste. What's scaring me now is how the after-market radio is wired in (I'm hoping they used a harness adapter, but after seeing the lights, I'm not so certain). I ultimately need to piggyback off the wiring there (or use a fuse tap from the inner box) to power/control a VFD clock from a Camry I picked up (the clock on the radio is too dim to see in the daytime).
 
  • Like
Reactions: Chris
Hey!

I understand there is a bus bar under the Maxi Fuses, so they are powered up, but I would like to ask how are the mini fuses powered in this PDC ?
 
I'd just buy a complete fuse box from a wreck, pull out the terminals with short sections of wire still attached and butt splice that to the end of whatever I was wiring up.
Just being cheap... I located one for for $42 shipped but was hoping to pick up a bag of connectors for $10 instead...
 
You can pick them up for much less than that once you figure out what they are.
$42 to my door seemed fair vs Getting up on Saturday morning, gathering some tools, driving to the pick-a-part, paying the entrance fee, miraculously find a Jeep on the first visit and paying for the PDC.

However, I am sure with your resources and influence you could find one on Craig's list and somehow manage convince a guy to pay for it, drive it to 60 miles to your house and drop it off with a smile on his face.
 
$42 to my door seemed fair vs Getting up on Saturday morning, gathering some tools, driving to the pick-a-part, paying the entrance fee, miraculously find a Jeep on the first visit and paying for the PDC.

However, I am sure with your resources and influence you could find one on Craig's list and somehow manage convince a guy to pay for it, drive it to 60 miles to your house and drop it off with a smile on his face.
So, I'll see you when?
 
  • Haha
Reactions: minimull
This write-up was performed on an XJ, but the concept (and a lot of the diagrams) should be very similar to a TJ.

The motive is to use the existing fuse holder and existing relay holders in the Power Distribution Center (PDC).

I got no ABS, so the whole top row (as shown on the diagram) is empty in mine.

There's also plenty of fuse spaces.

Go get a PDC at the junkyard that matches yours.

Relays are gone but the boxes are everywhere.

View attachment 5214

Remove your positive terminal from the battery, and the feed to the PDC from it's main terminal.
There's 2 metal tabs to remove the PDC from the body (big screwdriver)
Then 6 tabs to remove the bottom cover.
That's all that's in mine, if you got a lot of options, power windows, power doors, all that, you probably are a little fuller in there.

View attachment 5215

View attachment 5216

View attachment 5217

Remove the cover from the bottom of the bus.
These are things you should start doing first on your junkyard PDC, so you get used to breaking the little tabs off, and realizing how you should have removed it without doing that.

View attachment 5218

So looking down through the main fuse bar, you can see the empty holes have no metal terminal in them, you need to get the little connectors out of the JY PDC and put them in yours.
I should have taken the other fuses out for this pic so you can see what I mean.
Take a picture of your fuses & relays so you know where to put them back...

View attachment 5219

This is the JY box, the bus (the main terminal in the PDC) has been removed. It's just plugged into every slot, so work it with a screwdriver out of there.

View attachment 5220

Remove the bus plugs, the little metal inserts.
There's little slots in the front that catches a tab on the metal part, then it slides right out the bottom.
The first one isn't coming out easy, but start cutting the junkyard box open if you have to and when you get the first one out look at the little catch on the side of the bus plug. You have to hit that from the front, through the slot in the main housing.
Plug them up from the bottom, into your PDC.

View attachment 5221

In both pictures I have the yellow fuse center plate in, but that has to come out to do all this, and if you break any of the little tabs, the yellow thing isn't going back in right.
So don't do that.

Also, look at the bus and the last fuse spot at the main terminal, where it plugs in is the opposite side, so consider that when you're putting your bus plugs in.

View attachment 5222

You need to get a good bit of the wiring pigtail when you get your junkyard box to reuse the wiring & connectors.
By now you've shredded your JY PDC.

View attachment 5223

Plug those into the bottom of yours.
There's different wire sizes, pay attention to that for what size relays you're going to use, which you would figure out using the first chart.
I was able to add 3 new fused hot leads, and will be taking them straight to a new relay bank.

View attachment 5224

Each row is independant of the box, and again with the little tabs that break super easy.
The yellow part comes off first, 2 tabs from the bottom.
Then the black part pushes through the bottom, with 2 tabs on each side of the top.
So I ditched the 2 large relay spots, for a row of the (4) 30a ones [4671168].
There's a little nub I had to chop off so the 4 bank fit where the 2 one was.

View attachment 5225

View attachment 5226

So since everything hot is right there, I'll do a ground trigger.

View attachment 5227

The 3 new hot leads are the 30s, tie each 85 to that to power the switch.

View attachment 5228

The yellow/brown/green are my 3 86s to the cabin, the big reds are my 87's.
I'm only using 1 for now, to do my driving lights, the other 2 are for future.

View attachment 5229

View attachment 5230

So here's the new arrangement. New bank of 4 across the top. Only 3 of those are wired up, only 1 of those is in use.

View attachment 5231

All I have to do is plug in fuses & relays, and these two are 30A feeds.

View attachment 5232

I also made an extra 60A fused lead with no relay, for a future inside relay box.
It's not hot until I plug a fuse in that last position.

View attachment 5233

Testing out my switch at the battery.
The brown is the one I'm using, the yellow and green will switch the future relays.

View attachment 5234

And finally...

View attachment 5235
Much appreciate you sharing this space saving setup !
- Please don’t get me wrong , but in your schematic, connection # 85 is internationally recognized as (negative / ground)
- I just want to avoid confusion, or did I just confuse anyone 🥴😂
- I’ve seen it on occasion reversed with # 86, on different manufacturers brands
- it’s one of those cases where it pays off to check polarity with a test light or voltmeter, before the smoke escapes the wires 😂

~•|||||•~👋🏿
 
This site contains affiliate links for which Jeep Wrangler TJ Forum may be compensated.
Amateur question... I noticed that some of the maxi fuses are as low as 20 amps. What is the rationale for maxi fuses in the 20amp range vs the mini fuses? 12 volts is 12 volts and 20 amps is 20 amps, why the difference in approaches?

I have not yet cracked open my PDC for this project but know the maxi fuses have larger gauge leads which could come in handy and allows for higher amperage should the need arise. I don’t believe maxi fuses come in anything less than 20 amp. Is there anything else to consider regarding the mini vs maxi fuses at lower amperage?
 
Last edited: