Raspberry Pi red light

Question

I have a Raspberry Pi B+ connected to an external USB disk, a Seagate Portable 1 Tb (no external power source).

Everything is working fine, but when the disk is writing/reading data, the red light (power) blinks, sometimes. But I don't have any power loss, or corrupted data.

I've tested with 3 different power sources:

1) a generic one, that blinks (5V 3A)

2) my original charger from Galaxy S4 (5V 2A) does the same

3) a Galaxy Tab 3 charger (5V 2A) the red light keeps always off

Since the original Samsung chargers are trustable, I believe that my external HD is using too much power? But if this is true, why Raspberry keeps on and I got no corrupted data?

The red light blinking but everything working fine is a real problem? Or can damage it in some weeks or months? Maybe I need consider stop using an external disk?

Thank you.

Answer 1

According to the wiki:

Red power LED is blinking
A blinking red power LED indicates problems with the power supply. On model A and B, it is hard-wired to the 3.3V power supply rail. If it is blinking, as one user has reported1 it means the 5V power supply is dropping out. Use a different power supply.

On model B+ (and presumably also the A+), the circuit has been improved to give a much more reliable warning of poor power quality. The red power LED is wired to an APX803 supervisor[2] which kicks in when the 5V power supply drops below 4.63V[3]. If it does, the LED will blink. Check your connections, cable, and power supply.

Answer 2

The raspberry pi 3B+ also seems to use the red pwr led as a error indicator !

I have a SD card (Apacer 16GB) that came with the pi, preloaded with noobs 245. This card however does NOT work with the pi. When using this card: red pwr led on, NO green light, but after a few secs the RED led starts flashing a code every few seconds: 4x long, 3x short than on again.

So NO Power problem (5A supply, steady at 4.97v) ! This flashing red led only happens with this SD card, other SD cards boots OK....