Yes, absolutely. A relay can be faulty even if you hear an audible click when it's activated. The click only indicates that the relay's internal coil is energizing and its mechanical components are moving, not necessarily that the electrical contacts are making a proper connection or conducting electricity effectively.
Understanding How a Relay Works
A relay functions like an electrically operated switch. It typically consists of two main parts:
- Coil (Electromagnet): When current flows through the coil, it creates a magnetic field that pulls a lever or armature.
- Contacts: These are the actual switching elements. They open or close circuits when the coil is energized or de-energized.
The "click" you hear comes from the mechanical movement of the armature as it's pulled by the energized coil, causing the contacts to change position.
Why a Clicking Relay Can Still Be Bad
The presence of a click confirms that the coil is functioning and the mechanical mechanism inside the relay is still moving. However, it does not guarantee that the electrical circuit being controlled by the contacts is actually completing or operating correctly. Common reasons a clicking relay can be faulty include:
- Worn-Out Contacts: Over time, the metallic contacts inside a relay wear down due to repeated operation, arcing, or excessive current. This wear can reach a point where the contacts no longer make sufficient physical contact with each other, even though the armature moves.
- Oxidation and Contamination: Exposure to air, moisture, or contaminants can cause oxidation or a build-up of residue on the contact surfaces. This creates a high resistance path, preventing current from flowing, even if the contacts appear to be touching. The resistance can be so high that it effectively acts as an open circuit.
- Insufficient Contact Pressure: Even if the contacts touch, they might not do so with enough pressure to ensure a low-resistance connection, leading to intermittent operation or voltage drops.
- Internal Damage (Beyond Mechanical Armature): While the main mechanism might click, an internal component related to the contact itself (like a spring that applies pressure) could be fatigued or broken.
Identifying a Faulty Clicking Relay
If you suspect a relay is bad despite hearing a click, consider these common symptoms and diagnostic steps:
- Component Not Activating: The most obvious sign is that the device or circuit the relay controls does not turn on or off, even though you hear the relay click.
- Intermittent Operation: The device might turn on sometimes but not others, or it might flicker, indicating a poor or inconsistent connection at the relay contacts.
- Dim or Weak Performance: If the device receives some power but not enough, it could be due to high contact resistance causing a voltage drop across the relay.
- Testing for Continuity: The best way to confirm a bad relay is to test the continuity across its load contacts with a multimeter while the relay is energized. If the relay clicks but the multimeter shows an open circuit (no continuity) or very high resistance across the normally open (NO) contacts (or continuity across normally closed (NC) contacts doesn't break), then the contacts are faulty.
A relay will produce a click as long as its coil is receiving power and its internal mechanism is intact, regardless of whether a load is attached or if its electrical contacts are functioning properly. Therefore, always investigate further if a component isn't working as expected, even with an audible click.
