The RED ACC wire is often found in the instructions for installing an Android headunit.
You will find this guide helpful if you don’t know what the ACC wire is for or what to connect it to.
There is a red wire on the connector block labeled ‘ACC,’ but what is the ACC wire for?
Where do you find the ACC wire?
What do you connect the red ACC wire to?
Will the Android head unit still work if I don’t connect the RED ACC wire?
ACC is for Accessories
Accessories is a position in the ignition key lock just before the click that turns the engine over. But what has that got to do with an Android headunit? The Accessories position on the ignition switch makes a part of the car’s electrical circuits ‘live.’ Typically this would be the radio. But it can also be used to power a device or system that you only want active when the key has been turned in the ignition.
ACC is 12v
ACC is typically 12v for most cars and is only 12v when the key is turned to at least position 2 in the ignition. When the key is not in the ignition or turned enough to unlock the steering and not in the accessories position, the ACC wire in the car is normally 0v.
ACC uses
ACC is ideal for powering devices like a radio, android headunit, or an infotainment system of some description. ACC is often used in conjunction with BATT+, and with this ‘power pair,’ an android headunit can control the memory backup and accessories switch on. Where ACC turns the Android headunit on and off with the ignition key, the BATT+ will keep a permanent power on the headunit for a suspend-to-memory shutdown and subsequent fastboot at accessories on with the key.
Identifying the ACC line
ACC wire is often colored RED. It is found on the ISO power plug position A7. ACC will become live when the ignition key is turned to the accessories position and can be detected with a 12v circuit tester.
Other Names for ACC
ACC can also be named 12 VOLT IGNITION WIRE or just ignition wire. They all do the same thing, and ACC gets called ‘ignition wire’ because it becomes live with 12v when the car key is turned in the ignition barrel.
Anomalies
Some vehicle manufacturers use plugs and sockets that look like ISO standards and fit standard ISO plugs. But the wiring for ACC and B+ may not follow the standard ‘key in the ignition’ routine. This is due to computer control of the power in the car, and ACC wire may not behave the way you expect it for some models, such as later Volkswagen Group cars, Peugeot 106, Vauxhall Astra, Citroën C3, and some JCB tractors. Adaptors can modify this out-of-band behavior for ACC when doing your Android headunit install.
