[MOTORHEAD]

Good morning Andronikos, and happy Easter !The light to the right is the brake fluid level warning, so if you have topped that off and the light is still on, you have a wiring or sender problem.

The light to the left side is the ignition pilot light, which should extinguish when the engine is started (alternator running)
There should be a small yellow wire at the alternator (aux terminal) If the wiring checks out, it may be an internal problem with the alternator.

You said the charging voltage was running 15 v then went down to 14v Proper charging voltage should be 13.75 vdc to 14.25 vdc.

the "cog" belt is your accessory drive belt, not your timing belt and does not require the same tension as a "V' belt, but yours is too loose.