How to hardwire a dash cam for parking mode

Why this is necessary at all

Your 12V socket stops supplying power when the ignition goes off, on most cars. Parking mode needs power with the ignition off. That is the entire problem, and a hardwire kit is the entire solution: it takes power from a permanently-live fuse, takes a signal from an ignition-switched fuse so the camera knows the engine has stopped, and cuts itself off when the battery drops below a voltage you set.

If you do not want parking mode, you do not need any of this. The 12V cable in the box covers every collision you are actually present for. The battery page is the right place to decide whether parking mode is worth the afternoon.

What you need

• The hardwire kit for your camera. These are not universal. VIOFO's HK4 is USB-C and fits VIOFO's USB-C cameras; other makers have their own.
• Add-a-circuit fuse taps in the size your car uses — mini, low-profile mini or micro2. Look at an existing fuse before buying. Some kits include a full set.
• A plastic trim tool. A screwdriver will mark the trim permanently.
• A circuit tester or multimeter to find which fuse is which.
• Cable ties for the slack in the footwell.

No wire cutters, no strippers, no soldering. If a set of instructions tells you to cut into the car's wiring, stop and find different instructions.

The eight steps

1. Gather the kit. Everything above, on the passenger seat, before you start. The most common cause of an abandoned install is discovering mid-job that the fuse taps are the wrong size.
2. Find the fuse box and identify two fuses. Usually the driver footwell or behind a kick panel; the owner's manual has the location and the map. With a circuit tester, probe fuses with the ignition off to find one that is live, then turn the ignition on to find one that only becomes live then. Write both down.
3. Choose fuses that will not matter if they blow. See the note above. Also check the amperage: tap a 10A or 15A circuit rather than a 30A one, because the add-a-circuit is rated too.
4. Set the cutoff before you fit anything. Highest setting. On VIOFO's HK4 the options are 11.8, 12.0, 12.2 and 12.4 V, VIOFO recommends the highest as the safest choice, and it documents around 0.3 V of detection tolerance — so a nominal 11.8 could really be 11.5. Set it now, while the box is in your hand.
5. Route the cable. Start at the camera. Tuck the cable up into the gap where the headliner meets the windshield, across to the driver's side, down the A-pillar, then along the door sill trim into the footwell. The trim tool opens each gap enough to push the cable in; nothing needs to come off completely. Keep the cable out of the airbag path in the A-pillar — most cars have a curtain airbag there, and a cable routed across it becomes a projectile. Behind the trim and away from the folded bag is the rule.
6. Fit the fuse taps. Pull the original fuse, seat it in the lower slot of the add-a-circuit, put the fuse supplied with the hardwire kit in the upper slot, and push the assembly into the empty fuse position. Constant lead to the always-live tap, ACC lead to the ignition-switched tap. Getting these the wrong way round means the camera never enters parking mode, or never leaves it.
7. Ground it properly. Bare metal, bolted to the chassis. Not a painted panel, not a plastic bracket, not a seat rail that moves. Loosen an existing bolt, slip the ring terminal under it, tighten. A bad ground is the single most common cause of a hardwire install that works intermittently.
8. Test before you put the trim back. Start the car: the camera should power up normally. Switch off and remove the key: the camera should enter parking mode rather than shutting down. If it shuts down, the constant and ACC leads are swapped or the constant tap is not actually constant. Fix it now, while everything is still open.

After it is working

• Leave the car overnight and check in the morning. Confirm parking mode recorded, and confirm the car starts normally. That is the real test.
• Note which fuses you used. Write it on a slip of paper in the glovebox. In three years, when something electrical is odd, you will want to know.
• Check the recordings once a month for the first quarter. Parking mode fails silently, and a card that has quietly filled or corrupted looks identical from the outside to one that is working.

When to pay somebody else

Three honest cases. If the car is leased or inside a warranty period and you are not comfortable with the conversation, a professional install costs less than the argument. If the fuse box is somewhere awkward — some cars put it behind the glovebox or under the hood — the job stops being forty minutes. And if you are not confident about identifying the airbag path in the A-pillar, that is a genuinely good reason to hand it over.

Otherwise, this is a routing job and a fuse job. Nothing gets cut, and it all comes back out in ten minutes when you sell the car.