It depends on what kind of car you are working on, but it sounds like it can be an external voltage regulator, or even a fuse Some vehicles do not charge with out a rpm signal. The cause of the tach not working may also fix the alternator.
your alternator is not charging
Red means that the battery charge level is low or that the alternator is not charging battery properly. Check alternator, voltage regulator, connectors.
Odds are, Yes, the alternator is not functioning properly. Have the charging system checked.
Don't know this cars specifics, but usually, if the alternator light is on in your dash (the battery symbol) it means that your alternator is not charging your battery or that your battery cannot hold a charge.
If your battery is not charging properly the charging system warning light ( located just to the right of the " F " on your fuel gauge ) will light up . It is the picture of a battery
alternator is probably not charging. you need to fix this NOW. new alternator is likely the only repair.
It's most likely your alternator going out, or something wrong with the charging system.....
Charging system is not working properly. Have the alternator tested at any auto parts store for free.
alternator needs to be replaced. battery also might be a problem due to the alternator not charging it
charging system not charging battery with new batttery, alternator and fuel pump. what will make that happen ?
Is it charging, if not have you checked wiring to alternator.
Have the charging system checked. Possibly loose or corroded wiring, a loose alternator belt, or a bad alternator.