If the battey is dead it won't charge. But it sounds like the alternator is bad. If you're sure tha battery is good then it has to be alternator, wiring, connectors or switch.
where is the obd connection point on a 1992 thunderbird OBD1 is usually under hood by battery
check the charging fuse and the fuse able link on field wire
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.
Check a for a blown/burned out fuseable link between starter and alternator
It's most likely your alternator going out, or something wrong with the charging system.....
On a 1992 Ford Thunderbird : The gas tank is under the vehicle , just in front of the rear wheels
In 1992 the Ford installed manual transmissions in the Super Coupe ONLY, automatic was an extra cost option. Thunderbird, Thunderbird Sport, and Thunderbird LX, in V-6 or V-8 had automatic transmissions ONLY.
yes most MN12 Ford Thunderbird/Cougar parts as far as body will interchange
I just checked the owners manual and mine has an 18 gallon tank. 1992 Ford Thunderbird 3.8 liter.
On a 1992 Ford Thunderbird : ( both the 3.8 liter V6 engine and the 5.0 liter V8 engine have a timing CHAIN )
AOD
Disconnect the battery. Turn key to on, stick a long screwdriver through a hole in the bottom of the steering column and pull out the entire key cylinder