Automotive Service Excellence (ASE) A6 Electrical/Electronic SystemsGeneral Electrical/Electronic System DiagnosisMedium
A technician is diagnosing an intermittent issue with a vehicle's horn that occasionally does not work. When the horn does not work, the technician verifies there is battery voltage at the horn relay's control side power input and at its load side power input. The ground for the control side is also present. What should the technician check NEXT?
- AThe voltage at the horn button input to the steering column module
- BThe continuity of the wire from the relay's load side output to the horn
- CThe current draw of the horn circuit
- DThe resistance of the horn itself
Show answer & explanationAnswer & explanation
Correct answer: B. The continuity of the wire from the relay's load side output to the horn
If the relay has both power and ground on its control side, and power on its load side, it should click and send power to the horn when activated. If the horn still doesn't work, the next logical step is to verify if that power is actually reaching the horn, by checking the wire from the relay's output to the horn for continuity or an open circuit.
Why the other options are wrong
- A. The horn button input is part of the control side. Since the control side ground is already confirmed present, the button itself is likely functional, or its issue would be on the control side.
- C. Measuring current draw would be relevant if the horn was working but drawing too much/too little, but not for a 'no work' intermittent condition where power delivery is the primary concern.
- D. While the horn itself could be faulty, checking the circuit to it first ensures power is getting there. Resistance check is usually done with power off.
Relay Load Side Output
The terminal on an electrical relay that connects to the component (load) it powers, supplying switched battery voltage when the relay is activated.
- Supplies power to the load
- Activated by the control side
- An open circuit here prevents component operation
Memory trick: Power in, ground in, then check the load's spin.