If your vehicle is showing rattling or buzzing noise from behind the dashboard, here are the most likely causes and the parts you'll need to fix each one.
Leaves or debris can get trapped in the blower motor fan, or the motor's bearings can wear out. This causes a buzzing or rattling noise that changes pitch with the climate control fan speed.
The small electric motors that control airflow direction and temperature have plastic gears that strip over time. This causes a rapid clicking or buzzing sound behind the dash, especially when starting the car or changing climate settings.
Aftermarket radio or alarm installations often leave wiring harnesses or trim clips loose behind the dash. These unsecured components will rattle against the plastic panels when driving over bumps.
A failing electrical relay can rapidly click or buzz due to internal wear or poor voltage. This often sounds like a localized, electrical buzzing from the interior fuse box area.
Worn joints in the windshield wiper transmission can rattle against the cowl area just outside the firewall. The sound transmits through the firewall, making it seem like it is coming from inside the dashboard.