I recently got a Raspberry Pi 3B+, and it booted just fine and worked properly. I also had a 12v latch solenoid (the solenoid worked when I connected it to a 9v battery). I connected one end of the solenoid to a 9v battery, and the other one to the 5v pin (physical pin number 2) of my Raspberry Pi, then I wasn't getting any HDMI display, and when I tried rebooting the Pi, it wouldn't boot. I've waited for a few days and tried again, and even reinstalled the OS on my SD card, but it's still not booting (no green light), but the red light stays on.
How can I fix my Raspberry Pi? Help is greatly appreciated.
connected one end of the solenoid to a 9v battery, and the other one to the 5v pin... how did you complete the circuit? ... in other words, where did you connect the other battery terminal? ... which battery terminal was connected to the solenoid?