Dash cams: installing one without a flat battery and stray codes

A dash cam is the most popular aftermarket device in a car and the most common cause of two complaints: “the battery goes flat overnight” and “strange faults appeared”.

Power: three options

From the accessory socket. The simplest and safest electrically. The drawback: on some cars the socket is dead with the ignition off, so parking mode does not work.

A permanent live from the fuse box. The camera records while parked. The drawback: a direct route to a flat battery; covered in the parasitic drain article.

A permanent live with low-voltage cutoff. The correct option for parking mode: the device switches off when voltage drops below a threshold and leaves enough charge to start.

The practical rule: if you want parking mode, only with a voltage cutoff. Without it a car left for three days will not start.

Where to connect it

Not into the first spare circuit. The fuse box layout is the primary source; covered in the fuses and relays article.

Never into airbag, ABS, or engine management circuits. That is not superstition: extra load and switching transients in a critical circuit are a bad idea.

Always through its own fuse of the appropriate rating.

Earth to a factory body point, cleaned back, not “the first bolt available”.

The most common mistake is a twisted joint instead of a connector. It corrodes, gives an intermittent contact, and in time produces codes in neighbouring systems; mechanics in the aftermarket equipment article.

Where to mount it

Behind the rear-view mirror — out of your sight line, with the camera looking centrally.

Inside the wiper sweep — otherwise the view is smeared in rain.

Not on the dashboard — reflections in the screen and overheating in the sun.

Not in an airbag deployment zone — on the passenger side of the dashboard that is a direct risk.

Hide the cable behind the pillar trim rather than running it across the cabin. And there too you need to know where the curtain airbag runs.

Heat

A separate topic in hot climates.

A lithium battery inside a dash cam degrades quickly in heat, swells, and can distort the casing.

Supercapacitor models are far more reliable in heat — they cannot record long without power, but with a correct installation that is not needed.

A dark dashboard in the sun gets very hot — another reason not to mount the device there.

What to check after fitting

1. Quiescent current 30 to 40 minutes after the doors close.
2. Read codes across every system — before and after fitting.
3. Confirm the car goes to sleep — modules should not stay awake.
4. After a week parked — does it still start normally.
5. Check the view — the camera must not obstruct your sight line.

In short

• Parking mode without a voltage cutoff flattens the battery in days.
• Connect through its own fuse and never into critical circuits.
• A twisted joint instead of a connector produces intermittent contact and stray codes.
• Never mount it in an airbag deployment zone.
• In a hot climate a supercapacitor beats a lithium battery.

Download the app — voltage and codes across every system after installation are read with an ELM327 adapter over Bluetooth SPP on Android.