How can I find out if it’s the steering wheel assembly or the motor in the fluid can ? Thanks

 

Are you talking about the wiper motor, or the squirter motor?

 

In either case, remove the connector and test for voltage while someone operates the switch that turns that "thing" on.

 

If its the wipers, note that the harness connection at the motor to the main harness (under the washer-jets cover behind the hood) can disintegrate due to UV exposure! The connector body is literally disintegrating around the terminals. If this is so, replacement connector shells can be bought at EasternBeaver.com. Mine in my 80 SA were shot. Make sure you wrap the new one with some sort of (eg) electrical tape to protect from sun...

Stu A
80GS
AZ