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Discussion Starter · #1 ·
What is this little black box and do they go bad? Right now it has 3 wires going out/in. A wire to the air horn, a wire to the battery and a grounding wire. The air horn not working and trying to figure out the problem. Thanks!
 

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it's a relay and yeah they do go bad any parts store will have them they are universal. They have 4 or 5 pins usually the 5 pins have the option of breaking the extra pin off if you dont need it.
 

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3 wires are not enough to make it work.
You need 4... B+, ground, switched B+, and output (your horn)
 

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'89 YJ 4.2 with MC-2150 Carb & HEI, 2-1/2" Ex. AX-15, NP231 SYE, Adams shafts, F&R ARB, 3
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3 wires are not enough to make it work.
You need 4... B+, ground, switched B+, and output (your horn)

Just asking, but with the horn being grounded to the frame doesn't he only need the 3 wires ? or does he need to ground the relay to the frame or the horn also?
 

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You will need a minimum of 4 wires. One is Relay Coil ground, one is Relay + to actuate the Coil. One has to go to the contact +12V and one has to go to the horn from the contact.
 

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The relay needs to have a ground to activate.

These relays are for a homemade headlight harness but are probably the same relays.
The connections are shown in the schematic on the side of the relays.


Good Luck, L.M.
 

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Just asking, but with the horn being grounded to the frame doesn't he only need the 3 wires ? or does he need to ground the relay to the frame or the horn also?
There is an electromagnet in the relay that requires pos and neg to activate.... there are five terminals on most of those relays. Two of those terminals are for the electromagnet. One is for constant power. The last two are for load. When the electromagnet is not energized the constant positive is connected to one of the load terminals and when the electromagnet is energized the constant positive is switched to the other terminal thus energizing the electromagnet can either make or break the connection or even switch the connection from one to the other such as low beam high beam.
 

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Discussion Starter · #9 ·
First of all, thank you all very much for your help. It's nice to know I can come here and ask these relatively dumb questions and people are nice enough to answer and try to help!I'm so new at doing anything with cars but I love the challenge.

Now, I learned a little more this weekend playing around and in the process killed my battery and had to have it jumped. First, there are 4 wires. See attached picture. One to the battery, one to the horn, one to the harness going in to the headlight and then one wire that isn't attached to anything. I assume that's the grounding wire as discussed but what do I attach it to? I try putting it on a screw or any metal and the horn still doesn't work. Second and what's most interesting to me is that if I take all of the wires out of the relay and touch the battery wire and horn wire, the horn sounds. However, that's what shorted my battery (I guess?).

Finally, I bought a new relay and tried that. No luck. I also took the horn cap off and the 3 screws under the cap off and cleaned the circular metal. No luck. When I hold a screw driver to the metal push rod and push it down, it does make a click like it's getting some charge. I just don't know.

Thanks again for your help @Luckymac, @MannyN, @ got it at last and @Gottagofast ! I just want a horn that works.

 

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wmacson,

Do you have a test light and/or multi-meter? Either one can show you if your "hot" wire has juice or not, or if current is flowing through relay or not.
 

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'89 YJ 4.2 with MC-2150 Carb & HEI, 2-1/2" Ex. AX-15, NP231 SYE, Adams shafts, F&R ARB, 3
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OP hasn't posted what he has yet, but he should have a horn relay on inside firewall, next to fuse block for early model, or PDC on later, has that been checked out and or missing, bypassed, we're getting into "Bubba Hack Territory". Not sure how/why the relay was relocated.
 

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Bubba added an air horn. That seems to be the beginning of OP's misery.

Good Luck, L.M.
 

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'89 YJ 4.2 with MC-2150 Carb & HEI, 2-1/2" Ex. AX-15, NP231 SYE, Adams shafts, F&R ARB, 3
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OK, If its an air horn, Where is the compressor? How is it wired? Is that the spare wire not connected to anything? OP said he can get it to sound by jumping straight to battery.

I'm thinking no airhorn just a regular electric, Time for an overall setup pic or two.

https://www.wranglerforum.com/f218/a-better-way-to-get-help-in-the-yj-tech-forum-2341475.html

WMACSON, read the link above, fill out your signature with yr, Engine, Trans and any other cool stuff that may be appropriate so we have a better idea of what your working with. Then post a pic that includes your horn wires, relay etc. so we can help you track it down better.


FYI. Horn relay inside cab for 87-93 only has three prongs for wiring. 94-95 standard relay located in PDC.
 

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Discussion Starter · #14 ·
What a night! I finally got it. After all of your great advice and lots of reading, I realized it was probably that spare wire that needed to be grounded. I had tried before but I think i was doing it on rusty screws where there was little to no contact. Once I got it on a good bolt, it worked!

And just for the record, I bought the jeep about 2 months ago. The original owner had installed the air horn on the drivers side against the firewall and had it hard wired to the battery. Not ideal but at least i have a horn that works now.

Thanks again and Got it at last, i will definitely be filling in my signature with all my info. I have a lot to learn but i'm excited to keep trying.


Will
 

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'89 YJ 4.2 with MC-2150 Carb & HEI, 2-1/2" Ex. AX-15, NP231 SYE, Adams shafts, F&R ARB, 3
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What a night! I finally got it. After all of your great advice and lots of reading, I realized it was probably that spare wire that needed to be grounded. I had tried before but I think i was doing it on rusty screws where there was little to no contact. Once I got it on a good bolt, it worked!

And just for the record, I bought the jeep about 2 months ago. The original owner had installed the air horn on the drivers side against the firewall and had it hard wired to the battery. Not ideal but at least i have a horn that works now.

Thanks again and Got it at last, i will definitely be filling in my signature with all my info. I have a lot to learn but i'm excited to keep trying.


Will
There's a Dropbox link at the bottom of my signature that will have the FSM for your year, as well as parts catalogs that have exploded diagrams of which parts go in what order etc. Good info for getting you started.

Good luck and glad you got it figured out. The number one thing to check on anything Jeep electrical will always be your groundwire, They are notorious for becoming loose corroded etc.
 
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