when I had the instrument trim panel off (#3 in image) I removed the 4 retaining screws for the heater/AC control and pulled it out far enough to see the back of the switch

 

From looking at this fuse box diagram, I have at least four open relay slots in there:
2 ABS relay slots
1 between Starter Motor Relay and Fuel Pump Relay
1 ABS Main Relay
1 next to ABS Main Relay
1 Transmission Control Relay (? since I have manual, maybe)

Fuse slots 2, 4. and 12 should be open for a 30A fuse too.


Could go back to the junk yard and see how the harnesses look in the 2 XJs they have right now. My plug to the switch was cut off and replaced with individual connectors by a shop in 2004 or so after the original plug melted. Unlikely that the ones in the junk yard survived any better than mine, but worth a look.

Anyway, with a second harness I could run the best one from the switch and use the wires from the worst one through the firewall to the fuse box.

Edit: Well crikey! If I have this relay box under my dash it should be empty except for the horn relay, but it is a 1993 and mine is 1996:


https://www.cherokeeforum.com/f2/hid...r-dash-169543/

Update: I do have the second under dash relay block. Right side of steering column, in front of throttle pedal. Also looks like someone left a bunch of screws out of the knee board.

Looks like my layout is a bit different than the diagram.

So, the new plan is get a harness from another Jeep, run the wires from the switch to this block, add relays (are all automotive mini relays 30 amp?) then run my wires into the block and add a direct fused 30A wire to battery.

OR, bypass the ignition switch and get 30A fused from the cabin fuse block?
Another relay wired to the original 30A source that just controls power so I can't leave the fan running with key off?

 

Maybe I overlooked it in the thread, but did you, or are you, going to replace the blower motor switch? My '96 only had 2 speeds on the blower (hi was out on mine as well) when I bought the XJ a year and a half ago and I replaced the rotating **** in the AC control panel. Presto. I have 4 speeds + OFF again.

Extra details... it was melted along with the majority of the wiring, so I had to splice in about 6" of wire for each of the pins on the back of the switch. Kind of a real PITA because I had to chop off about 3" of original wire to get rid of the burnt stuff, so trying to splice wire to the cut ends was hard since it was kind of buried in the dash.

 

I'm not sure yet. Need to dig into that a little more. All I did as of now was pull the heat/ac control out enough to see it had a fried wire on the bottom terminal.
Maybe will practice on junk yard Jeeps to see the best way of getting that controller unit out of there without busting plastic and losing cable ends.

New parts list:
Junk yard relay block
Junk yard blower motor wiring harness
Junk yard control head
Mini relays. Are all automotive mini relays 30A? Might as well get fresh ones though. I do have some from the junk yard etc.

 

FYI that entire AC control panel is extremely brittle (at least mine was). I had mine out and while I was messing around I broke it in half on accident. Probably from 25 years of hot cold hot cold hot cold... and its also not the beefiest piece of plastic either. I ended up getting a real nice used panel for like $65 on ebay with the switch in perfect shape, but I went a head and replaced the used/good switch with a brand new one. I did that instead of hitting the JY to find one. I knew it would take 2 days to get the ebay one mailed to me, or I could take possibly 3-4 days or longer finding one in good shape in a JY, probably having to look in more than one JY.... Oh and it was dang near winter here in Denver when it happened, so I wanted a new control panel ASAP to get that heat flowing in the cabin.

I actually got my Mr. Buddy propane heater and set it in the cargo area of the XJ on low for about 20 minutes with the back windows cracked about 6" and cracked the front ones when I got out there so I didn't asphyxiate on propane gases. But it was nice and toasty in the jeep while it was about 30° outside. Also used my big dewalt construction site lights standing up in the back seat. That was PLENTY of light from the 2 big halogen bulbs, and it also created a decent amount of heat. It was actually fun because I was working in there with my whiskey and coke and a small tool box in the passenger seat with assorted small screwdrivers, electricians tools, etc... And turned my phone on the the ESPN app so I could listen to football games!!!

 

Maybe even less complicated, but I still want to get one from the junk yard to lay everything out and practice before messing up the one in my vehicle. One of these complete with full harness from my Pull-A-Part should be $43.47 and I might as well load it up with relays from anything I come across.
Relay Center C242 (located right behind rear wiper switch and cigar lighter) seems to be the key to fixing this with mostly parts that came from the factory. Especially if you have a Sport model, no power locks, no heated back window, like mine.
Not sure yet how many of the cavities are wired, but this shows the wire colors for the ones that would be used with factory accessories. The only ones I am using are C, F, and J.

Need to figure out how to have a main relay triggered by key on, the same instances the blower works now, to supply 30A to the other four relays without butchering things too much.

The harness to the blower resistor pack should reach the box as mounted and a full harness for this thing has plenty to reach the switch.

 

I know your method sounds better, but I would be inclined to follow my method for several reasons, the primary one being;

your custom harness needs 8 wires, 4 have to be thick

I just did mine in the most simple way I possibly could

reading a few of these notes on crisped wires and switches, I am relieved mine is done

make sure to use heat shrink insulation on all relay terminal leads

 

If yours can't come on without the key on then that eliminaeliminates part of why I took off on this path.

But where I am now all but one thick wire is already behind the dash.

 

I like to see different approaches anyway

mine cannot come on without the key...relays inputs are triggered by wires at resistor, ( I cant quite understand whether you want that or not ?)

 

I should really get around to installing relays on mine, I've seen the melted plugs on both of my Cherokee's. Maybe one day.

 

I do want it to work like stock. Having trouble visualizing your setup.

 

mine works and looks like stock

I will clarify a few points;

* the trigger (input) for each relay is each individual wire that leads to the resistor pack terminals. Detach the female spade..my harness contains male spades to plug into them. They will now only supply low current
* the output from each relay goes back to each resistor pack terminal
* the entire harness is wrapped in black tape, and hidden behind trim panels, mainly kick panel
* remove the kick panel...my relays are just nestled in their ! ..mine came fitted with bases and wires that make this easier, replace kick panel, its invisible
* As I mentioned, I chose to run a thick red wire thru a drilled grommet in the firewall, for reasons I outlined. This goes to a terminal for auxiliary 12V devices mounted by a PO in the engine bay
This wire is common power for each relay...so it is live all the time, but can only operate when the fan blower circuit becomes active

If you wanted a system that was totally isolated, you could add an extra key-triggered relay to supply 12V (via the fat red wire)

I dont like things to be too complicated..it should be fixable by some future owner..or me if I get dementia lol

also prefer that my modifications do not make things less reliable

 

I played around with this today https://www.digikey.com/en/resources...tools/schemeit and came up with this, if I decide to go with new parts. Today is the first time I tried to use one of these programs and the diagram is a bit of a hodgepodge. Those screw terminals are just there because I needed something that would accept more than one wire to the same component and I couldn't crack that code any other way. The stock wires are labeled with their Chrysler diagram colors. The red wires were added by me.


However, I am still planning on getting a Relay Center from Pull-A-Part and use it for my relay holder. I'm pretty sure I can mount it on the passenger side under the dash, sort of a mirror of where the original one is mounted. Hopefully there will be a resistor pack harness that is better than mine and I can use that for the harness from the switch to the relay block, then out of the relay block to the resistor pack.

I'd forgotten about a fat power wire I have under the hood, left over from fog lights that I've partly deleted. It goes through the firewall at an existing grommet on the passenger side, I just have to track down where it is going inside the cabin. It also has a fuse slot in the wire in the vicinity of the battery, needs a 30A fuse.

I also need to get some dashboard screws, because it appears that the folks in Northern, VA who were in there fixing the blower switch last, left all of them out along half of the bottom of the knee board. The original Relay Center is just sitting in there by the harness.

Thought it would be a good idea to have all the wires going in and out of the relay block be the ones for the blower, save for the big red one, just in case someone else has to get in there and do anything. Figuring out how to label everything without spending a mint on labeling equipment would be cool. Going to check with Staples and Office Depot to see if they have some workable options.

 

Excuse my ignorance of wireing up relays, did you ground anything to the chassis?

 

Yes, the relays need a good ground, I drilled one and added a self-tapper behind the kick panel

I suggest you download a diagram of how to wire relays from Google, that makes things easier