Repair Malfunctioning Car Horn

Indonesian: Memperbaiki Klakson (Bel) Mobil yang Tidak berfungsi
Case in: Daihatsu Ceria (Cuero)

If your car/motorbike horn is not functioning, you may want to try this troubleshooting.

1. Open machine bay cover
2. Push the horn button, and hear if there is relay "click" sound activating from the machine bay. 

 1). If there is no click sound, the malfunctioning part could be either the horn switch in your steering wheel or your relay is broken. You can confirm this using multimeter (Ohmmeter) measurement.

• Good switch shall be short circuit (around 0-4 ohm) when being pressed. See picture below on how to reach the switch. Open the screw behind steering wheel.

• Good relay coil shall have some resistance when being measured using ohmmeter. If it is read 0L (zero load), it is broken.

Less costly way to confirm all above is by short circuiting the correct trace.
To confirm whether the switch is broken: short circuit the both 2 switch terminal. If your horn beeps: the switch is broken. You can consider to replace or try repairing it. For myself, I have ever dismantle the switch and repair it by myself. It is always about misplace or dirty contact. Once the placement and/or carbon/dirt are rectified, it worked.

To confirm whether the relay is broken: 
a) Open the relay cover
     

b) Short circuit the relay switching terminal (push red arrow metal below using screwdriver towards blue arrow metal). If the horn beeps; your relay coil is broken. Replace the relay with the same current amperage rating.

   2). If there is "click" sound when you press the horn switch: either your 

• Loose wiring between relay and horn. Check if your horn lugs/crimps are tight. They are usually full of dust/soil if used to drive in harsh environment. Spray contact cleaner and scrape the dust/soil if necessary.
• Broken horn. Test this by supplying Battery+ wire 12V directly to your horn terminal. If it doesn't beep, replace your horn.
• Relay actuator fails... see following photo, there is black carbon/burnt residue disturbing the contact, and the contact circle is already thin. 

• 
  
  
  
• 
  

At this point you may consider to directly replace the relay with new good one. For my case, I prefer to extend the life for longer time. I clean away the carbon/burnt residue, and re-shape the contact circle.

•