When it comes to the most difficult part of vehicle repair, I hear it all the time, electrical systems. I will agree. When I was first learning automotive electrical repair and you asked me how to fix a car horn. I would have been confused on where to start.
But, just like everything else we learn in life such as learning to walk before running helps.
Electrical diagnosis can sometimes be challenging when trying to repair your own car. However, starting with a simple electrical system can help build your experience. You can learn how to read wiring diagrams as well as how to use simple tools.
While there are some complicated horn systems on vehicles today, most are generally very simple. We are going to start simple. We are going to walk through this basic horn schematic below and find out how we can test it and how to fix a car horn.
Parts Of The Horn System
As a simple circuit horns generally use only a few simple moving parts. The horn switch is the center of your steering wheel that you press to sound the horn. Think of this switch as operating very similar to the light switch in your house.
When you press the horn button the switch contacts close, which would be the same as turning your light switch on. Power is supplied to the horn and it sounds. When the horn switch is released the switch opens, and you guessed it, the horn stops.
There is also a clockspring and no, this isn’t the clockspring that powers your wristwatch. The clock spring sits behind the steering wheel and allows electrical signals to be transferred through a set of contacts while the steering wheel is rotated. This allows drivers to honk the horn while the steering wheel is in any position as well as have proper airbag operation at all times.
The horn is a mechanical device that converts electrical energy to sound energy. When you push down the horn inside of your steering wheel, a set of contacts closes. This operates very similar to a switch and provides a signal to your vehicle to turn the horn “on”
Wires And Connectors
The wiring in your vehicle is there to complete the circuit that is needed to sound the horn. There will be various connectors through the circuit. These connectors allow larger harnesses to be connected together. This allows easy manufacturing of the vehicle and diagnosis.
Every electrical circuit on the vehicle requires a power source. When we are trying to understand simple electrical circuits the battery will be our power source for operating the horn.
How to Diagnose a Car Horn
The circuit that we are going to be using for this walkthrough is very simple, if you are diagnosing the horn of your vehicle. Please find the correct wiring schematic before beginning, these will be found in an easy to use online service manual. While your schematic may look different, the basics of the circuit will be the same.
The first thing to verify is the voltage of the battery, after all it is very important that we have a fully charged battery when testing any electrical circuit.
Testing The Battery
Check the voltage of the battery by placing the leads of an automotive multimeter between test point 1 and test point 2 (The positive and negative posts of the battery). Compare the voltage that is present with the battery state of charge chart here.
Testing For Voltage At The Horn
If your battery is fully charged the next thing that you need to test is if there is voltage supplied to the horn when the horn switch is pressed. This is going to take 2 people to complete this test. Remove the connector from the horn before completing this test. Using a test light for electrical testing, attach the ground lead to the ground terminal of the battery and the test probe of the test light to test point 4.
When the horn is pressed the switch closes and allows power to flow from the battery through the switch and to the horn. The test light should illuminate. If the test light illuminates, you know there is power being supplied to the horn and the wiring and switch to the horn are in good condition.
If the test light does not illuminate you will need to check the horn switch and wiring from the battery to the horn to locate the issue.
Test The Ground Side Of The Circuit
Once you have confirmed that the wiring and switch to the horn are okay you need to test the ground side of the circuit. We can use a test light to test this side of the circuit as well.
Attach the ground clamp of the test light to the positive terminal of the battery. Using the probe end of the test light check to see if the test light illuminates when test point 5 is probed.
The test light illuminates this means the circuit is okay and is able to flow to ground. If the test light does not illuminate you need to continue testing. Verify the ground condition of the ground side of the horn and wiring are okay.
When all of the tests passed and you have verified the wiring and horn switch you will need to replace the horn.
Replace The Horn Assembly And Retest
After you have replaced the horn make sure that you test it to make sure it works correctly.
Hopefully this gives you a better idea of how to fix a car horn. Remember when it comes to learning electrical, take it slow and make sure you understand the basics.
If you have any questions about this diagnostic procedure. Or have found something weird during your testing please leave a comment below.