Dash cam · hardwire kit · add-a-fuse

Dash cam hardwire kit: wiring it to the fuse box

A hardwire kit frees the cigarette lighter and lets the camera record while parked. It has three wires: permanent +, ignition-switched ACC and ground. The work is choosing the right two fuses and putting the taps in the right way round.

Open the editor · ▶ Run the live demo

The three wires

• B+ (often yellow): permanent +, live with the key out — powers parking mode. Tap a permanent fuse such as the hazard lights or interior light.
• ACC (often red): + only with the ignition on — tells the camera to start and stop recording. Tap the radio or cigarette lighter fuse.
• GND (black): a bare-metal bolt on the body, not a painted bracket.

Add-a-fuse: which way round

Find the supply side of the slot with a test lamp (the ignition decides which: test both sides with the original fuse out). The tap’s leg without the fuse in it goes into that supply side, so the car’s original circuit and the new wire are each protected by their own fuse. Use 2–5 A for the camera — it draws under 0.5 A.

Do not tap these

• Airbag (SRS), ABS, ECU and fuel pump fuses — a fault in the camera wiring must never touch them.
• A fuse that is live only while cranking.
• Set the kit’s low-voltage cut-off (often 11.8–12.4 V) so parking mode cannot leave you with a flat battery.

See also: Fuse box wiring · 12 V socket and USB wiring

See it in the simulator

1. Run the live demo: a permanent fuse, an ACC fuse through the ignition, and the dash cam hardwire kit.
2. With ACC off the camera is idle but B+ is live; turn ACC on and it starts.
3. Click the wires: under 0.5 A — a 2 A fuse is plenty.

Questions

Why does my dash cam not switch off with the car?

ACC is on a permanent fuse, or B+ and ACC are swapped. Check the ACC tap with the key out — it must be dead.

Will parking mode drain the battery?

A camera takes about 0.3–0.5 A, roughly 10 Ah a day. Set the cut-off voltage, and on cars that sit for days use a timer or turn parking mode off.

Can I just splice into a wire behind the radio?

You can, but an add-a-fuse is cleaner, removable and fused. Never splice into airbag or CAN wiring.

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