Does the horn relay control anything else?

The horn relay is a critical component in a vehicle's electrical system, primarily responsible for activating the vehicle's horn. However, the horn relay may also control or interact with other vehicle systems, depending on the specific make and model of the car.

What is the Horn Relay?

The horn relay is an electromechanical switch that is used to control the operation of the vehicle's horn. When the driver presses the horn button, the relay is activated, which then completes the electrical circuit and allows current to flow to the horn, causing it to sound. The relay acts as an intermediary between the horn button and the horn itself, allowing the horn to be operated with a relatively low-current signal from the button.

Does the Horn Relay Control Anything Else?

In some vehicles, the horn relay may also be responsible for controlling or interacting with other electrical systems or components. Here are some examples of what the horn relay may control:

• Headlight Flashing: The horn relay may be connected to the headlight circuit, allowing the driver to flash the headlights by pressing the horn button. This can be useful for signaling other drivers or getting their attention.


• Alarm System: The horn relay may be integrated with the vehicle's alarm system, so that when the alarm is triggered, the horn will sound to alert the vehicle's owner and deter potential thieves.


• Accessory Lights: In some cases, the horn relay may also control the operation of additional lighting accessories, such as fog lights or driving lights, allowing them to be activated along with the horn.


• Theft Deterrent System: The horn relay may be part of a theft deterrent system, where pressing the horn button triggers a series of actions, such as sounding the horn, flashing the lights, or even disabling the engine, to deter potential thieves.

It's important to note that the specific functions and connections of the horn relay can vary widely between different vehicle makes and models, so it's always best to consult the vehicle's service manual or a qualified automotive technician to determine the exact role and functionality of the horn relay in a particular vehicle.

What happens when a horn relay goes bad?

Symptoms of a bad horn relay include the horn not working at all, working intermittently, or sounding weak. You might also hear a distinct clicking sound from the relay itself when the horn button is pressed, or notice a burning smell from the relay area.
 
Common symptoms of a bad horn relay 

• No horn sound: The most common symptom is a completely non-functional horn. 
• Weak or intermittent horn: The horn may sound weak, or only work sometimes. 
• Clicking sound: You may hear a clicking noise from the relay when you press the horn button, which indicates it is trying to activate but failing internally. 
• Burning smell: A burning smell coming from the fuse box or relay area can indicate that the relay is overheating and failing. 
• Stuck horn: In some cases, a faulty relay can cause the horn to get stuck on, leading to a constant honking sound. 

Next steps
If you suspect a bad horn relay, the next step is to locate and test it, often found in the vehicle's main fuse box. A simple way to check the relay is to see if you can swap it with an identical relay from a non-critical circuit (like the fog lights) to see if the horn then works. If the horn starts working after the swap, the original horn relay is bad and needs to be replaced.

Can I bypass a horn relay?

Comments Section Yes, you'll be fine. I've done it before when a different relay has gone bad, swap the horn relay in and you're driving again until you get a new one.

What does the horn relay control?

A horn relay uses a low-current signal from the horn button to activate a switch that controls a high-current circuit, allowing the horn to sound without putting excessive load on the steering wheel's wiring. It acts as an electromagnetically-controlled switch, where a small amount of power energizes a coil, which then closes contacts to send full battery voltage to the horn. This prevents overheating of the horn button and the thin wires that run from the steering wheel to the front of the car.
 
How it works

• When you press the horn button, a small electrical current flows through the relay's coil circuit. 
• This current creates a magnetic field inside the relay. 
• The magnetic field pulls a switch, closing the contacts in a separate, high-current circuit. 
• This allows full battery voltage to flow from the power source through the relay's contacts and to the horn. 
• The horn is energized and makes its sound. When you release the button, the magnetic field disappears, the switch opens, and the current to the horn stops. 

Why a relay is necessary

• Protects the horn button and wiring: The horn button and the wiring from the steering wheel are not designed to handle the high current the horn needs. A relay allows the low-current switch to control a high-current load indirectly. 
• Ensures performance: By providing full voltage directly to the horn, the relay ensures a consistent and powerful sound, rather than a weak or inconsistent honk. 
• Prevents overheating: Without a relay, the high current could cause the horn button and its wiring to overheat, leading to burnout and electrical damage. 

Is the horn relay controlled by the horn button and or the BCM?

The horn relay can indeed be controlled by either the horn button or the Body Control Module (BCM). click image for an enlarged view Neither hom shown in the wiring diagram will work when the horn button is pressed.