How to Check a Relay Using a Multimeter (VOM)

🔧 Step 1: Measure the Coil

Measure the two coil terminals
If resistance is present (tens to hundreds of ohms) → OK
If the reading is ∞ (open circuit) or 0Ω (short circuit) → coil is faulty

🔧 Step 2: Apply Power to the Coil

Apply the correct voltage (12V / 24V)
Listen for a clear “click” sound

🔧 Step 3: Check the Contacts

NO (Normally Open):
- No power → open
- With power → closed (conductive)
NC (Normally Closed):
- No power → closed
- With power → open

📌 If the relay clicks but the contacts do not conduct → the relay is faulty

Common Relay Faults on Electric Forklifts (Field Experience)

Symptom	Cause
Relay does not pull in	Burnt coil, no control voltage
Relay pulls in weakly	Low supply voltage
Relay pulls in but machine does not run	Burnt contacts
Intermittent operation	Worn or oxidized contacts

Notes When Replacing a Relay on the Controller Board

✔️ Use the correct coil voltage (12V ≠ 24V)
✔️ Match the contact current rating
✔️ Prefer reliable brands (Omron, Panasonic, etc.)
✔️ Do not use a small relay for a large contactor circuit

Technical Conclusion

✔️ Relays are small components but extremely important
✔️ A faulty relay can cause symptoms similar to a controller failure
✔️ Always check the relay first before concluding that the controller is defective