Aftermarket Accessory Battery Draw
Aftermarket accessory battery draw means an added radio, amplifier, alarm, dash camera, remote start, lighting kit, tracker, or trailer module is using battery power after the vehicle is shut off. This can leave the battery dead overnight or after a few days.
Can I Drive?
fix-soon
Most Likely Causes
- 1
Accessory wired to constant power instead of switched power
An accessory connected to battery power all the time may stay awake after the key is off.
- 2
Amplifier, alarm, dash camera, or tracker not entering sleep mode
Some accessories have standby modes. A failed unit or wrong trigger wire can keep it powered continuously.
- 3
Poor aftermarket splice or added relay wiring
Scotch-locks, twisted wires, unfused power leads, or poor grounds can create parasitic draw or intermittent shorts.
- 4
Trailer wiring module staying active
Trailer converters and added tow wiring can draw current or short after water intrusion.
- 5
Accessory backfeeding a factory circuit
An incorrect install can feed voltage into a circuit that should be off, keeping vehicle modules awake.
How to Diagnose It
- 1
Perform a key-off parasitic draw test
Let the vehicle modules go to sleep, then measure current draw in series at the battery. Compare to the vehicle spec; many vehicles should be well under about 50 mA after sleep.
Tool: Digital multimeter or amp clamp
- 2
Disconnect aftermarket accessories one at a time
Unplug added radios, amps, alarms, cameras, lighting controllers, trailer modules, and remote starts while watching the draw reading.
Tool: Multimeter, trim tools
- 3
Check accessory power and trigger wiring
Verify constant power, switched power, ground, and remote turn-on wires are connected to the correct circuits.
Tool: Multimeter, wiring diagram
How to Fix It
Move accessory feed to the correct switched or fused circuit
Rewire the accessory so it shuts down when it should and is protected by the correct fuse.
Repair poor splices and grounds
Replace weak splices with proper crimp or soldered connections and secure grounds to clean metal.
Replace or remove the accessory that will not sleep
If an added module keeps drawing current after correct wiring is verified, replace or remove that accessory.
Mistakes to Avoid
- Do not replace the battery repeatedly without testing key-off draw.
- Do not pull random fuses without letting vehicle modules go to sleep first.
- Do not leave unfused aftermarket power wires connected to the battery.