This happened to me on a road trip in my 84 Cougar. It was a long time ago, but first make sure your belts are tight! But I believe you may need to replace the alternator. If the battery is old, its cheap insurance to do both.
usually that the battery isn't taking a charge. have the alternator checked, many shops will test the charging system for free
You probably have a bad alternator. Need to check the charging system.
had to replace the battery in my 2002 Mercury Mountaineer but now the theft light is blinking, it is cranking up. How can I stop it?
not charging the battery properly... check the alternator.
I have what looks like a battery light on my dashboard. What does this mean?
Get the alternator checked before your battery goes dead.
I can tell you that on a 2000 mercury cougar it is a fuse on the positive cable between the battery and the alternator
If the alternator is not working the battery gets discharged. In most cars a light will show on the dashboard - battery light icon, and this will suggest fault in the battery or alternator. You will need to start the car and check if it is charging the battery, and most garages will do this check for you
Needs new alternator.
it means your battery isn't charging from the alternator, could be a fault either with the alternator or your aux drive belt maybe snapped is the most likely causes
Battery light usually means alternator not charging. Most common solutions would be be a bad alternator, bad connection, or loose alternator belt. If the battery and alt test ok than check the connections to the alternator and battery. You may also have a battery drain (something that is staying on and killing the battery)
Change your alternator