6-Pin DC CDI Wiring Diagram: How Battery-Powered CDI Ignition Works

6-Pin DC CDI Wiring Diagram: How Battery-Powered CDI Ignition Works — interactive diagram. Open it in the editor to customise components and wiring.

This is a free printable 6 pin dc cdi wiring diagram: download the diagram as SVG or open it and print to paper or PDF.

A 6-pin DC CDI wiring diagram shows how the battery-fed ignition circuit connects the CDI unit, trigger coil, ignition coil, kill switch, and regulated power supply in small vehicle engines.

A DC CDI (Direct Current Capacitor Discharge Ignition) unit differs fundamentally from an AC CDI in one key respect: it draws its operating power from the vehicle's DC battery (or rectified DC from the charging system) rather than from a dedicated AC exciter coil on the stator. Inside the DC CDI unit, a DC-to-DC converter (inverter/boost circuit) steps the 12 V battery supply up to the 200–400 V DC needed to charge the internal capacitor before each ignition discharge.

This makes DC CDI systems dependent on a functional battery and charging system — if the battery is flat or the charging system fails, the ignition will not function. This is a key practical difference from AC CDI, which can produce spark from a magneto alone with no battery. As a trade-off, DC CDI systems offer more stable ignition voltage across a wider engine speed range, and the timing characteristics can more easily be controlled via electronic advance curves built into the CDI unit.

On a generic 6-pin DC CDI connector, the pins typically serve the following functions (pin assignments vary by manufacturer and model — always verify against the specific vehicle service manual):

Pin 1 — 12 V DC supply input (from battery via ignition switch and fuse).

Pin 2 — Ground (chassis/battery negative return).

Pin 3 — Trigger/pickup coil positive signal input. The trigger coil on the stator provides the timing pulse.

Pin 4 — Trigger/pickup coil signal return (reference).

Pin 5 — Ignition coil primary output. The CDI discharges its charged capacitor through this pin into the ignition coil primary.

Pin 6 — Kill switch input. When grounded (or in some designs, when open), this input disables the CDI thyristor, stopping ignition.

The trigger coil in a DC CDI system has the same function as in an AC CDI — it senses the flywheel's timing mark and provides the trigger pulse — but because the CDI's energy comes from the battery supply rather than the stator exciter coil, the trigger coil signal is the only thing provided by the stator.

This description is generic. Always obtain and verify the vehicle-specific wiring diagram before servicing any CDI circuit.

How to wire 6 pin dc cdi wiring diagram

Identify whether the unit is AC or DC CDI Consult the vehicle service manual. Key indicators of DC CDI: the ignition circuit includes a fuse between the battery and the CDI, and the CDI's power input wire goes to the ignition switch rather than directly to the stator. An AC CDI's power input comes from a stator wire, not the battery.
Verify battery and supply voltage With the ignition switch on, measure DC voltage at the CDI's 12 V supply input pin relative to the ground pin. A healthy supply reads 11.5–13.0 V (engine off, battery in good condition). Low supply voltage may prevent the CDI's boost converter from charging the capacitor to a sufficient voltage for reliable spark.
Test the trigger coil With the CDI disconnected, measure resistance across the trigger coil terminals (pins 3 and 4 in the generic description). Compare to the manufacturer's specification (typically 50–500 ohms). An open reading indicates a failed trigger coil or broken wire.
Test the ignition coil windings Measure primary resistance (CDI output terminal to coil ground) — typically 0.3–1.5 ohms. Measure secondary resistance (spark plug cap to coil frame) — typically 5 000–15 000 ohms. Values outside these ranges indicate a failed coil winding.
Check the kill switch circuit With the ignition on and CDI connected, use a multimeter to measure voltage or continuity on the kill switch input pin. In the 'run' position (switch open), the pin should not be grounded. In the 'kill' position (switch closed), the pin should read near 0 V. A kill circuit that is permanently grounded will prevent ignition from functioning.
Substitute the CDI unit as a last step CDI units are difficult to test directly. After verifying supply voltage, trigger coil, ignition coil, and kill circuit are all within specification, substituting a known-good application-specific CDI unit is the most reliable final test. Ensure the replacement matches the original in application, pin assignment, and timing characteristics.

Specifications

CDI supply voltage (typical)	12 V DC nominal (operates typically 7–16 V DC)
Internal capacitor charge voltage (typical)	200–400 V DC (boosted internally from 12 V supply)
Trigger coil resistance (typical range)	50–500 ohms (verify vehicle service manual)
Ignition coil primary resistance (typical)	0.3–1.5 ohms
Ignition coil secondary resistance (typical)	5 000–15 000 ohms
CDI supply fuse rating (typical)	5–10 A (verify vehicle specification)
Kill circuit type (common)	Ground-to-kill (switch grounds CDI kill input to stop ignition)
Pin count (this variant)	6; DC CDI also available in 4-pin and 5-pin configurations

Safety warnings

The ignition coil secondary produces 10 000–40 000 V. Never touch the spark plug cap, HT lead, or ignition coil secondary terminal while the engine is cranking or running.
Even though the DC CDI operates from a 12 V battery input, its internal boost converter charges the capacitor to 200–400 V DC. Do not open a CDI unit or probe internal capacitor connections — this voltage is dangerous.
Always disconnect the battery negative terminal before working on CDI wiring connections to prevent accidental shorts or sparks.
Ground the spark plug lead to the engine frame when cranking the engine for diagnostic purposes without attempting to start it, to prevent uncontrolled ignition of fuel vapour.
Keep hands and clothing away from the flywheel, kick-starter mechanism, and any belt or chain drive when cranking the engine for ignition tests.

Tools needed

Digital multimeter (DC voltage, resistance, continuity)
Inline spark tester
Vehicle service manual with CDI wiring diagram
Spark plug socket and ratchet
Electrical contact cleaner
Oscilloscope (optional; for trigger coil pulse waveform analysis)

Common mistakes

Installing an AC CDI in place of a DC CDI (or vice versa) because the connector is the same pin count — AC and DC CDI units are NOT interchangeable.
Chasing a no-spark fault by replacing the CDI first without testing the battery supply voltage — a low battery can prevent the boost converter from charging the capacitor adequately.
Overlooking a corroded or loose fuse in the CDI supply circuit, which causes intermittent ignition failure that appears to be a CDI fault.
Connecting a non-application-specific CDI that has different ignition timing advance characteristics, causing engine knock, power loss, or overheating.
Failing to reinstall the inline fuse after servicing, leaving the CDI wiring unprotected against short-circuit damage to the harness.

Troubleshooting

No spark; engine will not start despite battery being charged: Cause: Open fuse in CDI supply, failed ignition switch not passing battery voltage to CDI, failed trigger coil, or failed CDI unit Fix: With ignition on, measure DC voltage at the CDI supply pin. If absent: check fuse and ignition switch. If present, test trigger coil resistance. If coil and wiring are within spec and supply is correct, substitute a known-good CDI unit.
Spark only at low rpm; misses or fails at higher rpm: Cause: Battery voltage dropping under load, deteriorating CDI boost converter unable to fully charge capacitor at high charge/discharge rates, or high-resistance connection in supply circuit Fix: Measure battery voltage under engine load. Check all connections in the CDI supply circuit for resistance. A battery that holds 12.6 V at rest but drops below 11 V under load cannot supply the CDI adequately. Test or replace the battery.
Engine runs but kill switch does not stop it: Cause: Open-circuit in kill switch wiring or failed kill switch; kill input not grounding correctly Fix: Verify continuity of the kill switch and its wiring back to the CDI connector pin. With the ignition on, use a multimeter to verify the kill pin is pulled to ground voltage when the switch is activated. Repair or replace the switch or wiring.

Frequently asked questions

How is DC CDI different from AC CDI?

DC CDI gets its charging energy from the 12 V battery (boosted internally to ~200–400 V DC). AC CDI gets its charging energy from a dedicated AC exciter winding on the stator — no battery needed for ignition. DC CDI provides stable ignition across all rpm; AC CDI ignition voltage varies with engine speed. DC CDI is more common on larger, battery-equipped vehicles.

Will a DC CDI work if the battery is flat?

Generally no. DC CDI relies on the battery supply (typically 12 V DC via ignition switch) to power its internal boost converter. Without a battery voltage supply, the capacitor cannot charge and no spark is produced. Some DC CDI units will function on very low battery voltage (down to 7–8 V) but will not function with a completely discharged battery.

Can I interchange an AC CDI and a DC CDI of the same pin count?

No. They are not interchangeable. An AC CDI expects high-voltage AC from the stator exciter coil on its power input pin. A DC CDI expects 12 V DC battery supply. Connecting the wrong type will result in either no spark or potential damage to the CDI unit. Always identify the type before sourcing a replacement.

What does the kill switch do in a DC CDI circuit?

The kill switch typically grounds the CDI's kill input pin, which disables the thyristor's gate and prevents the capacitor from discharging — thus stopping spark production. Some DC CDI designs use an active-high kill input instead. Always verify whether the kill circuit is a 'ground-to-kill' or 'open-to-kill' design before modifying or replacing the switch.

How do I distinguish a DC CDI from an AC CDI on the bench?

With the CDI removed from the vehicle, measure resistance between the suspected power input pin and the ground pin. A DC CDI will show measurable resistance (the DC-to-DC converter's input) — often in the range of several hundred ohms. An AC CDI's exciter coil input pin will typically show no low-resistance DC path. However, the most reliable method is to consult the vehicle's service manual to confirm the CDI type.

Related diagrams

Free electrical calculators

Edit this diagram free in the online editor