① If the horn works and the headlights turn on. Use a screwdriver or wire to perform a spark test at the negative terminal of the ignition coil. If no spark appears, there is an open circuit between the low-voltage terminal of the ignition coil and the ammeter.

Conduct spark tests in the sequence: ignition coil switch terminal → ignition coil switch-power terminal → ignition switch → ammeter. Locate the open circuit according to whether a spark occurs. If the connection between the terminal and wire is loose or poorly contacted, clean the terminal and tighten the fixing nut. If a wire segment is broken, replace it with one of the same specification.

② If the horn does not sound and the headlights do not light up. Use a wire to test for spark at the starter terminal. If a spark is present, the fault lies in an open circuit between the starter terminal and the ammeter. If there is no spark, the cause is insufficient battery power or a battery circuit fault. Recharge the battery if power is low; repair and reconnect any broken circuit wiring.

③ Use a screwdriver to test for spark at the negative terminal of the ignition coil. If a spark appears, test again between the movable contact arm and the base plate of the distributor. If spark occurs, the fault lies with the breaker contacts (such as burning, dirt buildup, or failure to close). Fix the problem by polishing the contacts with a contact file and adjusting the contact gap. If no spark is found, proceed to the next step.

④ Perform a spark test between the insulated terminal of the distributor and the distributor housing. If no spark occurs, the wire between the distributor insulated terminal and the ignition coil negative terminal is open. If a spark appears, there is an open circuit in the wire between the insulating bracket and the insulated terminal.