B737-800
Flight Crew Air Transport Pilot (ATP)
Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Flight Crew FLC Overrode Automation; Flight Crew Returned To Clearance
Aircraft
While flying the GLASR ONE Arrival into SEA; the LNAV appeared to malfunction and didn't make the turn to 163 degrees at the HETHR intersection. I proceeded to select heading to have the autopilot make the turn. The heading select button was unresponsive. I then disconnected the autopilot and made the turn. While in the turn; Approach asked about our heading.
We were on the GLASR ONE arrival into SEA; the LNAV disconnected and did not make the turn south to 163 degrees at HETHR intersection. The Captain was flying pilot used heading bug to make the turn and still no response; he then disconnected the autopilot and hand flew the turn. After the turn the controller asked what heading we were on. I told him 163 degrees. Nothing further was said.
B737-800 flight crew reported that their aircraft did not make the turn to 163 degrees at HETHR on the GLASR1 arrival to SEA. Heading select was engaged with no effect then the auto pilot was disengaged and the aircraft turned manually.