It's worth verifying that the test mode connectors are not connected... Near the wind shield wiper motor, there are 2 one wire connector sets. One set is green, one set is white. They should NOT be connected for normal operation.
These cars can be inexpensive - IF you do all your own repairs, and you collect lots of spare parts. Many parts are NLA from dealers or aftermarket. I run 2 so I have transportation when one has a problem, as often, parts are not in stock anywhere... Except what I have collected in my garage.