As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
HDG SELECT LIGHT OUT. ACFT GROUNDED. UNABLE TO DUPLICATE. HDG SELECT LIGHT OPERATES CORRECTLY FROM LIGHTS TEST SWITCH ON P1 PANEL. PERFORMED MCP INSTALLATION TEST IAW AMM 22-11-34-740-801, TEST PASSED. PERFORMED DFCS MCP INTERFACE TEST (BITE GRP 60.50), REF B737-800 FIM 22-11 TASK 802, HDG SELECT LIGHT PERFORMED CORRECTLY. CHECKS GOOD FOR SERVICE.