TheSiLvAPython Posted August 4, 2022 Share Posted August 4, 2022 i have a 1989 4.0 2wd and on the fourth of july had electrical short happen and ever since i have been dealing with issues and I'm almost to the point of giving up because I can't seem to figure this out. my headlights don't work, blinkers keep shorting out and blowing fuses. one brake light stopped working my fuel gauge works above 1/4 of a tank. i don't know where to start and I have an electrical service manual for 1989 year but it has not been much help because I don't quite understand it. i have multiple melted wires my fuse box is a wreck. how difficult is it to rewire everything from the fuse block to the tail lights? I really don't want to but i did buy 300 ft of wire but everytime i look at my fuse block and all the melted wires it is very intimidating. is there any advice or tips that could make this a little easier? i can post some pictures in a little bit to give a better visual of what i got going on. Link to comment Share on other sites More sharing options...
DirtyComanche Posted August 4, 2022 Share Posted August 4, 2022 I think you're better getting a known good harness. Somebody will have one for sale, or maybe pull one from a yard for you if you pay enough. You could pull the harness you have and look it over the on the bench/repair it, but please don't be offended by this, from your post I suspect you wouldn't have a good time doing this. I'm curious what caused everything to go wrong to start with, you might want to try to figure that out so you don't have a repeat. Manual transmission leaking brake fluid from the clutch master cylinder? Ground issues? The headlights are known to burn up the dimmer switch and lots of people put relay harnesses in for this reason. You should probably post up the pictures so we can see if there's anything obvious that might have lead to this. Link to comment Share on other sites More sharing options...
TheSiLvAPython Posted August 4, 2022 Author Share Posted August 4, 2022 20 minutes ago, DirtyComanche said: I think you're better getting a known good harness. Somebody will have one for sale, or maybe pull one from a yard for you if you pay enough. You could pull the harness you have and look it over the on the bench/repair it, but please don't be offended by this, from your post I suspect you wouldn't have a good time doing this. I'm curious what caused everything to go wrong to start with, you might want to try to figure that out so you don't have a repeat. Manual transmission leaking brake fluid from the clutch master cylinder? Ground issues? The headlights are known to burn up the dimmer switch and lots of people put relay harnesses in for this reason. You should probably post up the pictures so we can see if there's anything obvious that might have lead to this. it all started when I connected these two Link to comment Share on other sites More sharing options...
TheSiLvAPython Posted August 4, 2022 Author Share Posted August 4, 2022 now normally that wouldn't have been an issue because there would be a fuse to blow right? well not so much because one night i blew fuse after fuse after fuse (fuse was for the tail lights and dash lights) then i ran out of fuses and it was raining so i temporarily(or atleast was suppose to be temporarily) I replaced with a copper wire so I could get home. and i forgot about it. so on the fourth of july i was spraying some undercoating stuff under my truck and i seen those two little male and female plugs and must have thought that I had been missing out on something with those two being unplugged so I plugged them in and later that night when i went to go work i quickly found out that i was most certainly not missing out on anything and in fact was avoiding electrical catastrophe. Link to comment Share on other sites More sharing options...
JYau Posted August 5, 2022 Share Posted August 5, 2022 I've done a lot of wiring in my career and when it comes to automotive electrical it is not by any means easy. It requires a lot of patience and you'll definitely need to consult your service manual. There are some sections in that manual that describe how to use and read the manual, don't overlook those sections as there is some important information in there. At a minimum you're going to need a multimeter to check your wiring. You'll be using the meter to check if a wire is shorted to ground or if it the wire is making good contact to the node that it should be connected to. To fix all the wires you basically have to identify which wires are bad, they can be good but shorted to ground or the wires could be blown open and need to be replaced completely. This can be difficult because each wire will have a crimp that seats into a connector etc. The service manual spells out which wires go where and they are all color coded. You're best bet is to disconnect everything and sort them out. For a big project like this I would even recommend tagging wires with labels to help keep things organized. The one by one measure the wire, is it shorted to ground? Does the wire connect to node A and node B etc.? Wiring can be tricky, don't make any assumptions, one wrong wire is all it takes. Link to comment Share on other sites More sharing options...
AZJeff Posted August 5, 2022 Share Posted August 5, 2022 2 hours ago, JYau said: I've done a lot of wiring in my career and when it comes to automotive electrical it is not by any means easy. It requires a lot of patience and you'll definitely need to consult your service manual. There are some sections in that manual that describe how to use and read the manual, don't overlook those sections as there is some important information in there. At a minimum you're going to need a multimeter to check your wiring. You'll be using the meter to check if a wire is shorted to ground or if it the wire is making good contact to the node that it should be connected to. To fix all the wires you basically have to identify which wires are bad, they can be good but shorted to ground or the wires could be blown open and need to be replaced completely. This can be difficult because each wire will have a crimp that seats into a connector etc. The service manual spells out which wires go where and they are all color coded. You're best bet is to disconnect everything and sort them out. For a big project like this I would even recommend tagging wires with labels to help keep things organized. The one by one measure the wire, is it shorted to ground? Does the wire connect to node A and node B etc.? Wiring can be tricky, don't make any assumptions, one wrong wire is all it takes. THIS, TIMES ONE MILLION. The BEST bit of advice given above is to get a REAL service manual for your model year, if you do not have one already. Chasing wiring issues without the manual and it's critical wiring diagrams is like trying to drive in a strange place without a road map (pre-GPS days). If you are not familiar with, and own, a multimeter to measure continuity and voltage, go on line and learn how to use one, and then go buy something that does the basic measurements. Automotive wiring of the era of the MJ does not require a fancy multimeter. Even the old "moving needle" type that Radio Shack used to sell will do the job, so the dollar investment isn't large. Link to comment Share on other sites More sharing options...
JMO413 Posted August 5, 2022 Share Posted August 5, 2022 Those two connectors are for the licence plate light. Filling this out will help also others help you. Link to comment Share on other sites More sharing options...
Eagle Posted August 6, 2022 Share Posted August 6, 2022 I would look for a wiring harness from an '89 or '90 Cherokee. Yes, the tail light and brake light wiring is different in the MJ, but with the electrical manual that's an easy adaptation. Link to comment Share on other sites More sharing options...
TheSiLvAPython Posted August 9, 2022 Author Share Posted August 9, 2022 yeah this is difficult I have never done something Like this. actually this truck has been alot of "first time"s for me.It's cool I'm learning but it always overwhelming the first time changing a rear main seal or motor mounts/transmission mounts or welding a broken parts when the only thing I have done before on any of my vehicles is change spark plugs/brake pads/oil/coolant and sound system. I have taken the slow approach to this I because there is a lot of melted mess. I tried wiring up my dash lights to my new switch and switch connector and for some reason my dash lights only come one when I hit my brakes.... so i am very confused. because I have the wires labeled on the switch connector to what the go to. I don't know its weird. this is what the old switch connector looks like. I will show what the fuse box looks in a bit. Link to comment Share on other sites More sharing options...
TheSiLvAPython Posted August 9, 2022 Author Share Posted August 9, 2022 no my license plate wires are already plugged in these are spliced in or something one is ground and the other is power. Link to comment Share on other sites More sharing options...
TheSiLvAPython Posted August 9, 2022 Author Share Posted August 9, 2022 On 8/5/2022 at 4:09 PM, JMO413 said: Those two connectors are for the licence plate light. Filling this out will help also others help you. Link to comment Share on other sites More sharing options...
TheSiLvAPython Posted August 9, 2022 Author Share Posted August 9, 2022 On 8/5/2022 at 11:02 PM, Eagle said: I would look for a wiring harness from an '89 or '90 Cherokee. Yes, the tail light and brake light wiring is different in the MJ, but with the electrical manual that's an easy adaptation. So could I get Just from the fuse block back? I'm a little confused on how the bulk head connector works. when I take the fuse block off none of the wires appear to come from or lead to the bulk head connector. Link to comment Share on other sites More sharing options...
JMO413 Posted August 9, 2022 Share Posted August 9, 2022 There should be 2 license plate lights. Link to comment Share on other sites More sharing options...
TheSiLvAPython Posted August 10, 2022 Author Share Posted August 10, 2022 yeah this is difficult I have never done something Like this. actually this truck has been alot of "first time"s for me.It's cool I'm learning but it always overwhelming the first time changing a rear main seal or motor mounts/transmission mounts or welding a broken parts when the only thing I have done before on any of my vehicles is change spark plugs/brake pads/oil/coolant and sound system. I have taken the slow approach to this I because there is a lot of melted mess. I tried wiring up my dash lights to my new switch and switch connector and for some reason my dash lights only come one when I hit my brakes.... so i am very confused. Link to comment Share on other sites More sharing options...
TheSiLvAPython Posted August 10, 2022 Author Share Posted August 10, 2022 8 hours ago, JMO413 said: There should be 2 license plate lights. I have two License plate lights. you just can't see the second one in the pictures sorry about that. Link to comment Share on other sites More sharing options...
TheSiLvAPython Posted August 10, 2022 Author Share Posted August 10, 2022 I got Headlights, turn signals and brakes. still no dash lights or parking lights. Link to comment Share on other sites More sharing options...
JMO413 Posted August 10, 2022 Share Posted August 10, 2022 Do you have tail lights? Sounds to me like you still have a short somewhere. These electrical gremlins are always a pain. I chased them on mine for a long time. Link to comment Share on other sites More sharing options...
Guyverix Posted August 20, 2022 Share Posted August 20, 2022 Worse comes to worse, since you are in Washington if you are close to the Lake Stevens area, you can poke at mine and maybe trace stuff back on a more intact system to see what needs to be done on yours. I am in the middle of cleaning up my electrical as well. Chasing down a short from the parking brake that ends at the fuse panel. Cleaning that stinking mess out right now.. :) 1986 Comanche 1991 Wrangler Link to comment Share on other sites More sharing options...
Guyverix Posted August 20, 2022 Share Posted August 20, 2022 Also if you do get stuck pulling a harness, I BELIEVE the yard in Arlington has a mostly intact 1989 Cherokee sitting in the back, if that would be compatible with your rig or not, I have no idea. No dash in it (I grabbed that), but most of the wiring looks to be intact and in good shape. Link to comment Share on other sites More sharing options...
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