ACC out on my head unit died :(

**Chinasaur** · 07-30-2010, 10:33 PM

Hi all, my project is a little lower-tech than most of y'all. I'm just trying to use a microcontroller for more sophisticated control of my factory head unit. I was powering the micro off the ACC line at the back of my head unit (normally for CD changer); this worked fine for a few months but now it seems to have died. Head unit still works fine, but the ACC out line from the back is now floating.

Any thoughts on how I managed to kill this? Any hope for fixing the head unit itself, or should I try to pick up ACC somewhere else? I guess this time around I should set it up to run off the BATTERY line and use a transistor to switch on ACC to be safe, but I really don't understand how I managed to overstress the ACC line with a micro in the first place...

Head unit is 2008 Corolla Factory: A51813, Panasonic 86120-02430.
Thanks!

**soundman98** · 07-30-2010, 11:28 PM

being that the radio still works fine, pull the acc signal from the radio harness--before the radio.

not sure how much power a 'micro'(what is a micro?) takes, but last i remember reading about it, most of those amp-control out lines have a max current of around 0.5-1a...

**Chinasaur** · 07-30-2010, 11:33 PM

Ah, sorry: micro is microcontroller. I don't think I could possibly have pulled that much with the micro so the line must have shorted somehow although I'm not sure how; the wiring seems clean.

Is there a nice way to get the ACC line before the radio, like can I buy some plugs somewhere to build a new connector? Or does everyone just splice the lines? If I pull the ACC line before the radio, can I assume that line is properly fused so I don't have to worry too much about another short?

Thanks!

**Chinasaur** · 07-31-2010, 10:38 PM

Hmm, my reply doesn't seem to have posted yet. In the end I couldn't resist, so I ended up opening the head unit and as expected there was a burnt trace on the circuit board. I soldered separate wires to either side of the burn and ran them out the back so I can potentially put a fuse in there or something. For now I just connected them and everything is working again.