Bluetooth audio retrofit

• What the car’s audio system could and couldn’t do as delivered.
• What you wanted it to do instead.
• Why you went the retrofit route rather than replacing the head unit outright — or, if you did replace it, what drove that.

• What had to keep working — factory radio, steering wheel controls, chimes, backup camera, anything on the same bus.
• Whether the install had to be reversible, and why that mattered.
• Budget, and what parts were actually available for this vehicle.
• Physical constraints — where a module could live, what you could route behind, what you were unwilling to cut.
• What you had to figure out yourself because no documentation existed for it.

This is the section that decides whether the project reads as engineering or as parts-swapping. Detail is worth more than polish here.

• Where the audio signal enters the existing system, and what determined that injection point.
• How the module gets power, what it draws, and how you handled ignition-switched versus constant power — including anything about parasitic draw.
• Protection: fusing, and what set the rating.
• How you identified the right wires in the harness — service documentation, probing, measurement, or something else.
• Whether any bus signalling was involved (CAN, LIN, resistive-ladder wheel controls) and how you dealt with it.
• Anything you measured to make a decision, and what the measurement said.

• Order of work, and what had to come apart to get access.
• How you made the connections, and why that method.
• How you secured and routed the harness — heat, moving parts, chafe points.
• Where the module ended up and how it’s mounted.
• The part that took longest, and why.

• What you tested, and how you confirmed nothing else broke.
• Audio quality — noise, alternator whine, ground loops, and what you did if any showed up.
• Any current-draw check after the car sat.
• What surfaced only after weeks of daily use.

Video slot. Fifteen seconds of the system working — phone connecting, controls responding — carries more than three paragraphs. A phone clip is fine.

Two or three specifics. The strongest version names a decision, the alternative you’d now take, and what taught you the difference.