The wipers on my Project 87 IROC (wired with a 91 Trans Am harness) work at low and intermittent speeds only. No high speed, they just stop. When turned off they stop where they were at, mid windshield etc and do not park. They will park if I activate the fog light switch. Changed two motor assemblies and circuit boards on the motors. Checked the wiring under the column, motor ground also. Could the contol arm switch in the steering column be faulty? Ideas, suggestions? Thanks.