If sparks and black smoke were emitted from your outside A/C unit immediately after the power was turned back on following the replacement of the capacitor, it indicates a significant electrical issue. Here are a few possibilities of what might have happened:
Wiring issue: It's possible that there was a wiring problem during the capacitor replacement. If the wires were improperly connected or if there was a short circuit, it could have caused sparks and smoke when the power was restored. Faulty or damaged wiring can pose a serious risk and should be addressed by a professional.
Capacitor installation error: If the capacitor was not installed correctly, it could have resulted in a sudden electrical surge when the power was turned on. This surge might have caused the sparks and smoke. Capacitors store electrical energy and need to be handled carefully during installation to ensure proper functioning.
Component failure: It's also possible that another component in the A/C unit failed simultaneously or shortly after the capacitor replacement. The sparks and smoke could have been a result of a malfunctioning component, such as a motor or a compressor, rather than the capacitor itself.
In any case, the best course of action would be to immediately turn off the power to the A/C unit and contact a licensed HVAC technician. It is important to prioritize safety in situations involving sparks, smoke, or electrical issues. A professional technician will be able to assess the situation, identify the cause of the problem, and perform any necessary repairs or replacements.
Do not attempt to troubleshoot or repair the unit yourself, as working with electricity without proper training and expertise can be dangerous.