How do you Test ignition module 1991 thunder bird super-coupe?

Best advice is to get the Harley Shop Manual for your particular year Sportster. They have a 3 page diagnostic chart in mine for 1998. Follow through the test procedures outlined to tell if the ignition module or a related part is bad.

You may need to make a special wiring harness test cable to be able to check certain voltages while the module is connected.