TM 9-2320-364-20-2 2-1418 29.  HORN DOES NOT OPERATE (CONT). Reverse lights operate   indicating circuit breaker CB3   OK. Cab heater operates indicating   22 to 28 vdc is input to circuit   breaker CB16. Circuit breakers CB3 and CB16   are not tripped. Horn grounded. Circuit breaker CB16 OK. Wire 1026 OK. Wire 1031 OK. Horn button OK. Steering column ground OK. Wire 1016 OK. Harness wire 1016 OK. Horn relay R3 faulty. Wire 1168 faulty. KNOWN INFO POSSIBLE PROBLEMS TEST OPTIONS REASON FOR QUESTION Voltage test. STE/ICE-R #89. If 22 to 28 vdc are not measured, horn relay R3 is faulty. If 22 to 28 vdc are measured, wire 1168 is faulty. YES NO Replace relay R3 (Para 7-95). Verify repair, go to Step 11 of this Fault. 10. Are 22 to 28 vdc measured at horn relay R3, terminal 87 when horn button is pressed? Repair wire 1168 (see schematic Fig 2-36) or notify DS Maintenance. Verify repair, go to Step 11 of this Fault. WARNING Reverse lights operate   indicating circuit breaker CB3   OK. Cab heater operates indicating   22 to 28 vdc is input to circuit   breaker CB16. Circuit breakers CB3 and CB16   are not tripped. Horn grounded. Circuit breaker CB16 OK. Wire 1026 OK. Wire 1031 OK. Horn button OK. Steering column ground OK. Wire 1016 OK. Harness wire 1016 OK. Horn relay R3 OK. Wire 1168 OK. KNOWN INFO POSSIBLE PROBLEMS TEST OPTIONS REASON FOR QUESTION Verify repair. If horn operates, fault has been corrected. YES NO Fault not corrected. Notify DS Maintenance. 11. Does horn operate? Fault corrected. Read   WARNING on Page 2-1419