If your vehicle is showing burning plastic or electrical ozone smell from the dashboard, here are the most likely causes and the parts you'll need to fix each one.
The resistor that controls your A/C and heater fan speeds gets extremely hot during normal operation. If it fails or the fan motor draws too much power, it can melt its plastic wiring connector, pushing a strong burning plastic smell directly through the vents.
As the interior fan motor ages, its internal bearings wear out, causing it to work harder and draw excessive electrical current. This overheats the motor's internal copper windings, producing a distinct electrical 'ozone' smell.
Poorly spliced wires from a recently installed aftermarket stereo, remote start, or car alarm can rub against sharp metal brackets behind the dash. This causes a short circuit that melts the wire insulation.
In many vehicles, high electrical current flows directly through the ignition switch. Over time, the electrical contacts wear out and create resistance, which generates intense heat and melts the surrounding plastic inside the steering column or lower dash.
A failing relay or a loose connection in the interior fuse panel can create electrical arcing. This generates an ozone smell and can slowly melt the plastic fuse box housing under the dashboard.