How do you troubleshoot an oil furnace transformer?

Troubleshooting starts with safety: power off, verify lockout, and check for fuel and ignition hazards. Inspect wiring, connectors, and the ignition electrodes for cracks, carbon tracking, or incorrect gap. Verify the primary supply voltage and control signal to the transformer. Then measure secondary output with appropriate high voltage test equipment or verify spark strength safely using manufacturer approved methods. Check for cracked porcelain insulators and moisture ingress. If there is weak or intermittent spark, overheating, buzzing, or visible arcing, replacement is often recommended rather than repair.