Hello and welcome to Just answer.com, Super mechanic here. About your vehicle.
There seems to be a little confusion about the vehicle.
88 or 98
Chevy or Ford
Sorry my fault. 88
I see. The 88 models didn't use a relay for the wipers. There is however, a pulse module, on the motor. Let me give you the tests for both types.
WINDSHIELD WIPERS INOPERATIVE
MOTOR OPERATES BUT WIPER BLADES DO NOT
WIPER BLADES STOP AT RANDOM POSITION ON WINDSHIELD
MOTOR INOPERATIVE AT LOW OR HIGH SPEED
MOTOR OPERATES AT ONE SPEED IN BOTH HIGH & LOW SWITCH POSITIONS
MOTOR INOPERATIVE IN DELAY MODE
MOTOR WILL NOT SHUTOFF
WIPERS STOP BUT DO NOT RETURN TO PARK
WIPERS PARK ABOVE NORMAL POSITION
Where is this module located on the vehicle?