UNL1MTD Posted June 4, 2007 Share Posted June 4, 2007 When i bought the truck the horn didn't work. I swapped in another and it appeared to be good. Over the course of the last month I have notices that it has been a little touchy to get the horn to sound. Today it mades its last peep. Now when I press the horn I hear the loud clicking from the relay and all other electronics in the truck either dim or stop working. The wipers freeze, the radio stops, the headlights get very dim, and the gauges do the same. Oh and the horn does not sound. I'm guessing there is a short somewhere, but I'm really at a loss. Any suggestions? Link to comment Share on other sites More sharing options...
HOrnbrod Posted June 4, 2007 Share Posted June 4, 2007 Pull your horn relay, then try to sound the horn. If no excess load seen on your other circuits, prolly the horn relay shorted internally. Link to comment Share on other sites More sharing options...
UNL1MTD Posted June 4, 2007 Author Share Posted June 4, 2007 Pull your horn relay, then try to sound the horn. If no excess load seen on your other circuits, prolly the horn relay shorted internally. good call. i'll give that a go tonight. Link to comment Share on other sites More sharing options...
HOrnbrod Posted June 4, 2007 Share Posted June 4, 2007 Pull your horn relay, then try to sound the horn. If no excess load seen on your other circuits, prolly the horn relay shorted internally. If pulling the relay cures the dimming lights, then most likely the problem is on the load (horn) side of the circuit since the lights dim. Stick the relay back in, crawl under the bumber and disconnect the horn(s) wires. Try sounding the horn again. If the lights still dim, the problem is an internal short in the relay or in the wiring between the load contacts of the relay and the horn. If the lights do not dim, the horn itself is internally shorted. I'm betting on the relay. Link to comment Share on other sites More sharing options...
UNL1MTD Posted June 5, 2007 Author Share Posted June 5, 2007 got way sidetracked yesterday and only pulled the wire off the horn. didn't fuss with the relay. it still loaded down all the electronics with the horn unplugged, so i guess its the relay. I'll have to pull that in the parking lot here soon to know for sure. Anybody know what color it is? I'm assuming its near the fuse panel. Link to comment Share on other sites More sharing options...
Eagle Posted June 5, 2007 Share Posted June 5, 2007 got way sidetracked yesterday and only pulled the wire off the horn. didn't fuss with the relay. it still loaded down all the electronics with the horn unplugged, so i guess its the relay. I'll have to pull that in the parking lot here soon to know for sure. Anybody know what color it is? I'm assuming its near the fuse panel. It could still be anywhere in the wire between the relay and the horn. In fact, if the relay clicks it is more likely NOT the relay itself, but that can be checked by plugging in a different relay. Link to comment Share on other sites More sharing options...
HOrnbrod Posted June 5, 2007 Share Posted June 5, 2007 It could still be anywhere in the wire between the relay and the horn. In fact, if the relay clicks it is more likely NOT the relay itself, but that can be checked by plugging in a different relay. X2. The horn relay is in PDC (at least on my 91), the cover tells which relay is for what. Link to comment Share on other sites More sharing options...
UNL1MTD Posted June 5, 2007 Author Share Posted June 5, 2007 Not sure what PDC stands for, but I popped the plastic cover off the thing that said 'RELAY CENTER' inside the engine bay on the passenger side. Found 3 blue relays and I had no diagram. Looks like there was one there at one point in time, but it was a sticker and washed off. No matter. The sound of the Relay is LOUD and inside the cabin, so I was confused as to how I could hear it in the engine bay when driving. I traced the wired from the horn, it is gray. No visible tears or cuts from horn to wiring loom. Loom goes from driver's headlight directly to the cabin. No where close to the 'RELAY CENTER.' So I look at the fuse box and there is a gray wire with a white relay attached to it. I pull it off. It only has three terminals which confuses me. Start up the truck. Honk the horn. No horn, all electronics happy. So I am going to try and fetch a new one of these today and see what happens. Maybe buy a new horn too. Is it possible that the reason the previous horn went bad was because of too much current going to it or something? I couldn't find a fuse in the fuse panel for the horn, is there one? Link to comment Share on other sites More sharing options...
Pete M Posted June 5, 2007 Share Posted June 5, 2007 PDC stands for Power Distribution Center or something like that. It's a fancy term for "fuse box". :D Your TJ has one, but your 87 MJ will have a separate fuse box and a relay spot. Link to comment Share on other sites More sharing options...
UNL1MTD Posted June 5, 2007 Author Share Posted June 5, 2007 PDC stands for Power Distribution Center or something like that. It's a fancy term for "fuse box". :D Your TJ has one, but your 87 MJ will have a separate fuse box and a relay spot. Yea my TJ definitely does, I guess thats a difference in the Renix/HO engine wirings. So I got the White thing in front of me. Couple markings on it. 25523703 along one side 7054 along another side F in a corner and thats it google says http://www.pacvette.com/store/store.pl?part=25523703 so I guess I'll get a replacement Link to comment Share on other sites More sharing options...
HOrnbrod Posted June 5, 2007 Share Posted June 5, 2007 I'm sorry UNL1MTD, I gave you bum dope. The horn relay IS near the fuse panel, (either taped into the harness along w. two other relays, or behind the kick panel, depending on year) in the cab. The part number (86-92) for it is J5764039, about $10 from the dealer. And according to my parts manual pic, it does have only three contacts. And here all this time I thought it was in the PDC. Again sorry........... :cry: And the horn is fused through the 25A Hd Lp Dly fuse (#11) in the PDC, according to my FSM. Link to comment Share on other sites More sharing options...
HOrnbrod Posted June 5, 2007 Share Posted June 5, 2007 Here's a schematic of the circuit: Link to comment Share on other sites More sharing options...
UNL1MTD Posted June 5, 2007 Author Share Posted June 5, 2007 Here's a schematic of the circuit: is there suppose to be two horns? on all years? I only got one. Its just on the driver's side. Link to comment Share on other sites More sharing options...
jpdriver1 Posted June 5, 2007 Share Posted June 5, 2007 yep one on each side behind bumper Link to comment Share on other sites More sharing options...
Pete M Posted June 5, 2007 Share Posted June 5, 2007 Maybe the other horn wire is touching metal? Link to comment Share on other sites More sharing options...
jpdriver1 Posted June 5, 2007 Share Posted June 5, 2007 I ran a gnd wire from each horn bolt when I added horns Link to comment Share on other sites More sharing options...
HOrnbrod Posted June 5, 2007 Share Posted June 5, 2007 is there suppose to be two horns? on all years? I only got one. Its just on the driver's side. The second horn was an option, but the wiring is there for both. High and Low tone horns. And yes, definitely check for a ground from the load contact of your horn relay (disconnected from the relay) to both horn wires (also disconnected). Your relay just might be good. Link to comment Share on other sites More sharing options...
UNL1MTD Posted June 5, 2007 Author Share Posted June 5, 2007 Maybe the other horn wire is touching metal? even worse...mrjeff87 will get a kick out of this... flashback 2 Sundays - I pop the hood and ask Jeff about this wire I had that the PO grounded to the chasis. I said everything seemed to be working but it just didnt look right. He said maybe its for factory fogs ... As soon as I saw that wiring diagram I knew that wire was indeed for the second horn. Disconnected it from the chasis and plugged the relay back in. :cheers: :D I got my horn back and at no cost! Thanks for everyone's help. Especially hornbrod for that wiring diagram. I'm thinking I might even add another horn so it sounds a bit meaner. Link to comment Share on other sites More sharing options...
HOrnbrod Posted June 5, 2007 Share Posted June 5, 2007 Glad you got it. Dayem, the Jeff-man should know better :cheers: :D The fuse should have blown though pulling that many amps. :nuts: Yeah, lose that "meep-meep" single horn and put something more manly in there. I stuck in a pair of huge 1965 Buick Electra 225 horns I had laying around - sounds like a city bus. Link to comment Share on other sites More sharing options...
mjeff87 Posted June 6, 2007 Share Posted June 6, 2007 Well, there ya go.....mystery wire solved :D Id'a never guessed it was a second horn wire....never knew it was an option :nuts: Kenny, I learned something today..... Now you got me thinking about adding a second horn to my MJ! Jeff Link to comment Share on other sites More sharing options...
broythomas Posted June 24, 2007 Share Posted June 24, 2007 My horn was out when I got my mj, the fuse kept popping on my 1992. I found out that the e-brake was knicking a wire next to it. A little electrical tape fixed the problem. It didn't effect my headlights, but there's several wires there. Mine came with one horn, but now has three. Had a couple of extras from an '85. Link to comment Share on other sites More sharing options...
UNL1MTD Posted June 24, 2007 Author Share Posted June 24, 2007 I just ran an aux horn today. Figured since I had the bumper off putting on the 'L' shaped tow hook bracket reinforcements, I might as well wire up another horn. Install was so easy and now I got more horn. Not quite like more 'cowbell' but it'll get the job done. Link to comment Share on other sites More sharing options...
mjeff87 Posted July 9, 2007 Share Posted July 9, 2007 OK....picked up a second horn at the 'yard yesterday, and hooked it to the same wire you had there Sean. Problem is, that wire on my MJ is 12V constant hot.......scared the bajezus out of me as soon as I touched the bracket to ground :oops: So I scrapped that idea and looked all around the passenger side where a second wire would logically be and couldn't find one. Can anyone help me find it? I suppose I could just run a jumper wire off the first horn to it and mount them in tandem on the driver side, but if the factory wire is there I'd like to use it..... Jeff edit: looking at that schematic, to my electronically-challenged brain, it looks like 4.0L's got the two seperate wires and the 2.5's only had a single wire to the driverside horn, with a jumper wire off it to the other one. Think I answered my own question, but can anyone verify that? Link to comment Share on other sites More sharing options...
UNL1MTD Posted July 9, 2007 Author Share Posted July 9, 2007 that pic shows the wire, its the exact same as the driver's side in color and connector type. wierd that the 2.5L and 4.0L are different. Maybe its cause the 4.0L is louder and they figured it would need more horn for people to hear it. :D Link to comment Share on other sites More sharing options...
mjeff87 Posted July 9, 2007 Share Posted July 9, 2007 You da man Sean......I just went out and looked again, and there was the wire, buried inside the split loom with all the other light wiring harness. I remember it was hanging down when I pulled the bumper to relocate the vac canister, and I stuffed it into the loom to get it out of the way (doh!) Not sure now why that scematic shows the 2.5 wiring as a jumper wire, but oh well, I got what I needed! Link to comment Share on other sites More sharing options...
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