[shorod]

I don't have the wiring diagram for the 1989, but am using a 1992 diagram for reference and hoping they are similar (although the body style of the SHO changed in 1992).

At least for the 1992 model, the park and run functions are performed by the wiper motor assembly. For the interval wipers there is an "interval governor" box separate from the wiper motor. The troubleshooting guide indicates if the interval wipers work with the switch in the off position, the possible causes are an open condition in the wiper switch (in the wiper motor assembly) or an open condition in the Orange wire.

Possible causes for wipers that won't park are listed as an open condition in the wiper switch or no voltage to the wiper motor.

The common "cause" for both conditions is the wiper switch in the wiper motor assembly.

-Rod