How to Test a Snowmobile Coil in 5 Steps
Testing a snowmobile coil involves checking resistance with a multimeter to confirm proper ignition system function. Start by disconnecting the coil, then measure primary and secondary resistance against manufacturer specs. Look for open circuits, shorts, or values outside the recommended range. Replace the coil if readings are abnormal.
Tools You'll Need
- Digital multimeter (with ohms/continuity settings)
- Service manual (for spec ranges)
- Screwdriver or wrench (to remove coil)
- Safety gloves (to prevent shocks)
Step-by-Step Testing Process
- Disconnect the coil: Turn off the engine, remove the spark plug wire, and unplug the coil's electrical connectors.
- Set the multimeter: Switch to ohms (Ω) mode. Use the 20kΩ range for secondary resistance and 200Ω for primary.
- Test primary resistance: Place probes on the coil's positive (+) and negative (-) terminals. Compare reading to specs (typically 0.1-3.0Ω).
- Test secondary resistance: Attach one probe to the spark plug wire terminal and the other to the negative terminal. Expected range: 5,000-15,000Ω.
- Check for continuity: Switch to continuity mode. A beep confirms no open circuits; silence indicates a faulty coil.
Common Coil Issues & Symptoms
- Open circuit: Infinite resistance (no continuity). Causes no spark or intermittent misfires.
- Short circuit: Near-zero resistance. Leads to weak spark or overheating.
- High resistance: Readings above specs. Results in hard starting or poor acceleration.
- Physical damage: Cracks or burns on the coil housing. Replace immediately.
Coil Testing Methods Compared
| Method | Tools Required | Time Needed | Accuracy | Best For |
|---|---|---|---|---|
| Multimeter Resistance Test | Digital multimeter, manual | 10-15 minutes | ⭐⭐⭐⭐⭐ | Precise diagnostics |
| Spark Test (Visual) | Spark plug, insulated pliers | 5 minutes | ⭐⭐⭐ | Quick field check (risk of shock) |
| Substitution Test | Known-good coil | 20 minutes | ⭐⭐⭐⭐ | Confirming coil failure without tools |
Safety Precautions
- Always disconnect the battery before testing to avoid electrical hazards.
- Wear insulated gloves when handling spark plug wires.
- Avoid testing near flammable materials (spark risk).
- Never ground the spark plug directly to the engine-use a spark tester tool.
When to Replace the Coil
Replace the coil if:
- Resistance readings are outside manufacturer specs.
- There's no continuity in primary/secondary circuits.
- Visual damage (e.g., cracks, burns, or corrosion) is present.
- The engine misfires persistently after other checks (spark plug, wiring).