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Home >> GMC >> 1990 >> Forward Control 3.9 L >> Repair and Diagnosis >> Accessories & Equipment >> Cruise Control Systems >> Cruise Control System - Vacuum Servo >> Description & Operation >> Control Switch Operation >> Set/Coast

Control Switch Operation: Set/Coast

To set vehicle speed, turn control switch to ON position. With vehicle speed at 25 MPH or more, press and release SET/COAST button. Vehicle will maintain set speed.

To increase speed during engaged cruise, accelerate to desired speed. Press and release SET/COAST button. Vehicle will maintain new set speed.

To decrease speed during engaged cruise, press and hold SET/COAST button. System will disengage. When vehicle has slowed to desired speed, release SET/COAST button. Vehicle will maintain new set speed.

To decrease speed by one MPH increments during engaged cruise, tap SET/COAST button (quickly press and release button; DO NOT press and hold button). Vehicle speed will decrease one MPH for each tap of the button. System can tap down until it reaches low speed lock-out (25 MPH).