Horn problems come in many different flavors. They either don't work, are on all of the time, or only work when they 'want to'. Since it is not very cost effective for my customers to just start changing everything on the system and crossing their fingers to hope it works, there is some actual diagnosis that needs to be done. That is what I am here to explain to you how to do. If you want someone to tell you to just start changing things until it is fixed, then go read another article. Fair?
Okay, I see you are interested in getting things fixed right, the first time since you are still reading. So let's get down to the different types of problems and the diagnostic procedures that are associated with them. Before working on anything, the first thing to do is check the computer for codes. Many of today's cars have a body control module (B.C.M.) which play a big part in controlling the horn. So, you need to make sure that there are no trouble codes set. Not all trouble codes will turn on a warning light, so be sure to check them with the proper scan tool that can read codes from the body control module(not all of them can), if your vehicle has one. You also need to make sure that the different modules in the vehicle can communicate with each other. If there is a problem with communication, your scan tool will alert you. If you find any problems with those things, they need to be corrected before going any farther. If everything is 'all good there', then proceed with the inspection of the system.
To begin inspecting the horn system, here are the things you need to check:
* The fuse - If the fuse is blown, then there is a short in the system, and it needs to be found, or it will keep blowing.
* Check for improperly installed aftermarket accessories, such as radios or amplifiers and such, that might be spliced into the wrong circuits.
* Check for obvious damage to the related wiring, connections, and components that work the horn system.
* Check for corrosion or other debris at the point where the horn bracket is mounted to the vehicle. It can get in there and cause a 'bad ground'.
* Check the torque of the bolt holding the horn bracket to the vehicle. If it is loose, it can actually damage the horn, from a low voltage condition.
* Check for improperly installed aftermarket accessories, such as radios or amplifiers and such, that might be spliced into the wrong circuits.
* Check for obvious damage to the related wiring, connections, and components that work the horn system.
* Check for corrosion or other debris at the point where the horn bracket is mounted to the vehicle. It can get in there and cause a 'bad ground'.
* Check the torque of the bolt holding the horn bracket to the vehicle. If it is loose, it can actually damage the horn, from a low voltage condition.
If all of the basic stuff passed the inspection, then we move on to the 'problem specific' diagnosis. We will work with a horn that does not work in this article. Other problems will be covered in other horn related articles. Anyways, you will need a test light, and probably the repair manual for your vehicle to go much farther.
Okay, so you got your test light and repair manual. Let's get started with this basic run down on diagnosing a horn that does not work.
1. With the key off, remove the horn relay and check for power from the relay coil wire and an external ground source. If there is power there, move on to step 2. If not, then repair the wiring problem between the battery positive terminal and the horn relay positive terminal, and the horn will work.
2. Put the test light between the relay positive coil terminal, and on the relay control circuit (one that goes to the button), and press the horn. If it has power move to step 3. If not, then do you remember that clock spring I told you about? Well, there could still be a problem with the button, if there is no air bags in the vehicle. Look in there, and you will see the problem. If it has air bags, then the steering wheel needs to come off. If not then you can change the button, with a cheap kit from the auto parts store.
3. At the horn switch, check power between positive terminal and a good ground source. If there is no power, then there is a problem in the horn switch itself. If there is power there move to step 4.
4. Get a wire with a 15AMP fuse in it, and run it between the battery and the output terminal of the relay socket for about 1 second. If the horn operates, change the relay. If not, then put the relay back in the socket move to step 5.
5. At the horn disconnect it, and put the test light between the power wire to the horn and a good ground source, and press the horn. If there is no power there, then there is a bad wire between there and the horn control terminal on the relay. If there is power, move on to step 6
6. Hook the test light between the power and ground terminals on the horn (if it has 2 terminals), and press the horn. If there is power there, then replace the horn. If there is no power there, then there is a power int he horn ground circuit. Remember the B.C.M.? That would be a possibility, here.
If you follow these instructions, you should be able to get most any horn back in working order, if it is dead when you try to use it. Oh, yeah I forgot to mention, if you need some discounts on auto parts, as a thanks for reading, type of thing. To see the latest promotions from Advance Auto Parts, look at my profile page. They usually have a 20% off total purchase sale happening, if you know what you need and can buy it online then pick it up at the store. I am always happy to help, as I know how it is to need it and not have anybody to turn to.
I hope this article and my resources have been helpful to you. Have a good day and thanks for reading!
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