Is there a relay? Or is there a fan thermal-switch with a dark blue and black wire connector that is screwed into the radiator tank under the battery?
Understand that this is from my 1978 service manual and might be different than what you have.
By jumping the radiator-mounted thermal switch with a wire, the fan should run. It is in a series circuit with the fan motor. It can handle the current draw of the fan motor.
I know that on fuel injection cars if you unplug the 2-wire coolant temperature sensor that is mounted on the thermostat housing on the cylinder head, the PCM will default to 'fan on' and light the 'ck eng' light.
1983 might be too early for this feature.
It sounds like the radiator thermal switch may have failed open?