'96 Cherokee Power Distribution Center, PDC Disassembly

I don't know exactly which years this will apply to. It will apply to Grand Cherokees too, and probably a bunch of other vehicles. If anyone can offer insights as to the scope of the applications it would probably be worth mentioning.

For my own sake I have torn into this with the intent of putting to work some of the vacant space in my PDC as opposed to adding even more fuse blocks in the vehicle, but for the sake of this post this is simply a matter of what is present and how it comes apart. I would very much appreciate input on some details about relays, and if anyone knows where to get some of the connectors involved that would be great.

Here is what I have under the hood in my 1996 XJ:



Note that there are a bunch of empty slots for relays (mostly the smaller, rectangular type--anybody know their nomenclature and rating?) and empty slots for those large spade fuses. I see potential for a number of electrical upgrades while maintaining somewhat stock appearance. So what does it take to put this space to use?

New Year's day I got a couple of hours in the junkyard, and it was 50% off day. A couple of comparable PDCs followed me home. Both of these were out of Grand Cherokees, but I don't expect them to differ in construction.

One constant theme in my learning curve has been "this plastic is dang brittle". The years and heat cycles have not been good for this stuff. Plan to proceed with caution. The most important things to note are the locations of the release tabs. I have tried to take the best pictures I can to show where these tabs are and how to go about releasing them. Some of them I am still trying to get to release successfully. Brittle plastic is a pain.

The first step is getting the PDC out of its mount. There are two metal clips which need to be pried back and then the whole box needs to lift straight up. Here's a pic of the box still in its mount, showing the metal tabs which need to be pulled back:



This picture is to show what happens when you don't lift straight up:



Notice the broken out retaining flanges on the lower box (they are still intact on the upper box). It didn't take much force at all to accomplish that, and that is the primary mount for the box. This one (lower) became my candidate for destructive analysis right then and there. Don't make this mistake with the one you need under your hood.

Next step is removal of the bottom of the PDC. There are six clips around the perimeter. I found it helped to snip some thin pieces of sheet metal to help hold several of them open while I pried. I didnt' need all of them to release at once, but I needed more than I could accomplish with my own two hands. That is another theme in this process. There is a need for extra hands, but not much room for them to work in.

Once the bottom of the PDC is off then the plastic plate which retains the plated copper buss plate needs to come off. It is held on by three plastic hooks. I broke one of these right off the bat too, largely because I had no idea where they were or how to release them. Here are some pictures which should help with that:





I think the answer is to come at these though the square holes in the bottom of the plastic plate. A thin jeweler's screwdriver would probably be the ticket. The two which are together at the farthest end from the alternator lug will be the easiest and the ones to start with. Hopefully, with them loose, the one closer to the alternator lug will then be accesible. See the following pics for more clarification:







As for the material this buss plate is made of (particularly for 5-90's benefit), it is copper. It mics at 0.032" on the tabs and 0.066" on the bottom where it is doubled up. I would figure it is nominally 0.030" copper.

To be continued...

With the buss plate out of the way I went to work to figure out how to pull the connectors out of the box. The brittle plastic makes this an interesting challenge, particularly if you don't want to damage the box.

The yellow plastic pieces are retainers/locking keys for the tabs which keep the metal connectors in place. I like the security of the system. Nothing is coming out by accident. And the yellow plastic seems to have held up much better than the black. The releases for the yellow retainers at the buss plate end of the box can be accessed from the top of the PDC. I didn't have any trouble getting this one up and out.






Getting the connectors to come out the bottom is another story entirely. There are two locks holding each connector in place. One is a plastic lock which is part of the PDC main housing, the other is a metal tab which is part of the connector. Here are my tools and my success rate:





The tools are a modified 1/8" Craftsman screwdriver and a modified dental pick. In addition to cutting off the end of the screwdriver I also had to grind a bit off of one dimension in order to get it to fit. That's for releasing the metal tab. Note that even once released it still provides a bit of a fight. The leading edge is a burr and it catches/scrapes the plastic housing all the way out. Note the one which is folded all the way over backwards. They don't give up without a fight.

Note all those little black plastic clips. Those weren't supposed to ever come out. That's a function of the brittleness of the plastic. The dental pick is the best tool I have managed to find to catch the tips of those and pull them back. They have to be pulled back all the way to the far side of their opening in order to allow the metal connectors to pass. Good luck getting them to bend that far without breaking. It will be interesting to see if I can push connectors back in without those tabs breaking.

The intermediate connectors were an interesting find to me. They are the bridge between the buss plate and the fuses. The assembly goes like this:





I would love to know if someone knows how to get more of the connectors which go on the end of the wire. I can cannibalize all the intermediate connectors I need to add fuses, but I would love to start with new wire connectors if possible. That is not a connector I have ever seen before. If anyone knows anything about it, please share.

To be continued...One more post for the relay end of the box...

The relay end of the PDC is interesting in that it is modular. You could swap out one of the relay boxes for another one of a different configuration. These also seem to behave better than the buss plate end of the box. It somewhat figures that the easily replaced part would be the one that behaves...Good old Mr. Murphy.

Once again, the yellow plastic piece is the first part of the lock which must be removed. The releases for these are best accessed from the bottom of the PDC. Here are the two styles I have taken out, showing where the releases are located:



Note all the other plastic fingers sticking up. Those are to lock the release tabs for the connectors. Again, nothing is going to vibrate loose in there.

With the yellow pieces out of the way you can then remove the boxes which house the wiring for the relays. The releases for these are accessible from the top. I didn't know what I was working with on the first one, but had no trouble with the second one:



And here are their slots in the PDC box (It's not the best picture, but hopefully you can see where the locks slide in and catch):



Here are the two patterns I have for the relay mounts:





You should be able to see that the locks are still intact on almost all of the slots. I broke at least one, but had a much better success rate at this end of the equation. I have no doubt I can get these things apart with a 100% success rate.

Here are the wires and connectors. Note the alignment tab on the side and the square hole for the lock. Again, I would love to know if someone knows how to obtain new connectors:



I would also appreciate information on the three types of relays used. These are they:





The relay on the left is the one I am most acquainted with, but the middle one and the one on the right are new to me. What is their nomenclature and what are their ratings? I am particularly curious how many amps I can run through the little one on the right.

I am also curious as to the reason for the three sizes of blade fuses. I have all three of these in my '96:



20 amps at 12 volts should be 20 amps at 12 volts. Why did Chrysler see the need to use all three sizes of these? Can anyone offer any logic on this one? It is what it is, and I will be carrying all three sizes of spares, but, dang! :twak:

From what I have done playing with the junkyard PDC I think I can pull things apart successfully enough to add wires into an old PDC and thereby avoid adding yet another fuse box under the hood. Taking out the connectors in my own PDC is not something I would want to do, at least not at the buss plate end of the box. I wouldn't want to do that unless I had a brand new PDC housing and intentions of swapping everything over. The plastic is not a safe risk at that end.

I got a spare PDC from FitchVa years ago that I plan on doing the same thing with in my 96 trail rig. nice work and thanks for jump-starting my project again!