the power light on my pixma mg3620 just blinks and it won't respond to any buttons.

Diagnosis

The blinking power light on the Canon PIXMA MG3620 indicates that the printer is trapped in a "Fatal Error" state or is failing its internal POST (Power-On Self-Test) sequence. When the light flashes continuously without an accompanying alphanumeric error code on the small LCD screen (like E05 or P104), it typically signifies a hardware initialization failure. This happens when the printer's logic board cannot communicate with the print head or the carriage assembly, or when there is a power surge that has tripped the internal protection circuit.

In many cases, this is caused by a "stuck" carriage. If the print head cannot move freely to the home position during startup, the printer will enter this loop to prevent the motor from burning out. You can confirm this by listening closely during the blink sequence; if you hear a rhythmic clicking or a grinding sound followed by the blinking light, the issue is mechanical. If the printer is completely silent and the light just pulses, it is more likely a voltage issue or a corrupted firmware state.

How to Fix It

To resolve a logic lock or power surge error, you must perform a complete cold reset of the internal capacitors. Follow these exact steps:

1. While the printer is still blinking, press the Power button once to turn it off.
2. Disconnect the AC power cord from the rear of the printer.
3. Unplug the power cord from the wall outlet. If you are using a surge protector or power strip, remove it entirely and prepare to plug directly into a wall socket.
4. Open the front cover (the access door for the ink cartridges). Manually check if the carriage can slide from left to right. If it is stuck, gently nudge it toward the center. Ensure there are no torn pieces of paper or jammed labels in the tracks.
5. Close the cover securely.
6. Wait exactly 120 seconds. This allows the volatile memory (RAM) on the mainboard to clear.
7. Plug the power cord directly into a known-working wall outlet. Avoid using extension cords, as the MG3620 is sensitive to voltage drops.
8. Press the Power button once. Do not hold it down; a single firm press is required.

If That Didn't Work

• Reseat the Ink Cartridges: Open the cover and remove both the PG-245 and CL-246 cartridges. Inspect the gold contact points on the back of the cartridges for ink smears or debris. Clean them with a lint-free cloth and a drop of isopropyl alcohol. Reinsert them firmly until they click into place. A poorly seated cartridge can trigger a fatal boot error.
• Perform a Hard Reset via the Buttons: With the printer off, hold the Stop/Reset button (the red circle triangle) for 5 seconds, then release it and immediately press the Power button. This can sometimes force the printer to bypass a non-critical initialization error.
• Check for Paper Jam Sensor Trigger: Use a flashlight to look at the far right side of the printer where the carriage parks. If a tiny scrap of paper is blocking the optical sensor, the printer will blink and refuse to respond to buttons. Use a pair of tweezers to remove any debris from the encoder strip (the clear plastic strip running across the width of the printer).
• Test with a Different Power Cable: If you have another Canon printer with the same 2-prong power lead, swap them. A partial break in the internal wiring of the power cord can provide enough voltage to light the LED, but not enough to initialize the carriage motors.

Heads Up

• Avoid using "Generic" or "Compatible" ink cartridges that have modified chips, as these can occasionally cause communication errors that lock the printer's firmware.
• Never use a can of compressed air directly into the carriage tracks; this can push dust into the optical encoder strip, causing the carriage to slam into the side and trigger a fatal error.
• Always turn the printer off using the Power button before unplugging it from the wall to prevent corruption of the internal NVRAM.
• If the blinking persists after all these steps, the internal logic board has likely suffered a capacitor failure and the unit will need to be replaced, as the MG3620 mainboards are not modularly repairable.