Ok, what does THAT red thing mean?
---------- Post added at 08:51 PM ---------- Previous post was at 08:39 PM ----------
Ok, the internet says
"The Magic Eye® that is used in Motorcraft batteries provides 4 stages of indication, they are:
1. Green: battery is charged and the acid level is good.
2. Yellow: Battery is partially dis-charged and the acid level is good. Re-charge the battery or drive the vehicle.
3. Red: Battery is dis-charged and the acid level is good. Charge the battery.
4. Clear and bright: Acid level is low!!! Add distilled water if possible. If not, change out the battery. Do not charge or jump start the battery!!!
While the Magic Eye® is only located in one cell, it is still quite accurate for indicating the state of charge of all cells as they are within 95% of the same condition. If there is a catastrophic failure such as an internal short circuit, the battery would be bad, but the eye would still show green as the density of the acid is still technically correct. This is very rare."
So it must be true.