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
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?
You probably have a bad alternator. Need to check the charging system.
I have what looks like a battery light on my dashboard. What does this mean?
not charging the battery properly... check the alternator.
I can tell you that on a 2000 mercury cougar it is a fuse on the positive cable between the battery and the alternator
Get the alternator checked before your battery goes dead.
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
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
Needs new alternator.
Change your alternator
Your battery or alternator are not supplying enough energy. Get both tested at your local autoparts store.