B757 CREW AT FL320 HAS YAW DAMPER FAILURE WHICH CAUSES A SIGNIFICANT LEFT YAW AND EICAS MSG.

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IN CRUISE FLT AT FL320 FLYING AT .81 MACH; WE WERE JUST CLRED AFTER THE INTXN AND ZZZ. ACFT SUDDENLY VEERED TO THE L AND WE RECEIVED AN EMER DOOR MESSAGE AND YAW DAMPER EICAS MESSAGE. ACFT RETURNED TO STABLE FLT AND ONLY EMER DOORS LIGHT WENT OUT. FEW MINS LATER; EMER DOOR LIGHT CAME BACK ON. AT THIS TIME; WE DECLARED AN EMER DSNDING TO 15000 FT. WE BROADCAST OUR DSCNT. WE NOTICED MORE MESSAGES APPEARING ON EICAS; HOWEVER; UPON REACHING 15000 FT; ACFT WAS STABLE AND FLYING SAFELY. WE ELECTED TO FLY TO ZZZ; VERSUS ZZZ1 DUE TO THE FACT BOTH ARPTS WERE EQUAL DISTANCE; HOWEVER; FLYING TO ZZZ1 WOULD HAVE BEEN GREATER HEADWINDS. WE LANDED SAFELY AT ZZZ; WITH NO FURTHER PROBS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE AIRCRAFT WAS DISPATCHED WITH ONE YAW DAMPER ON MEL; RESULTING IN THE SHARP YAW WHEN THE SECOND FAILED. THE EMERGENCY DOOR WARNING MAY HAVE INITIALLY BEEN TRIGGERED BY THE YAW AND A VERY SENSITIVE MICRO SWITCH; HOWEVER NO DISCREPANCY COULD BE FOUND BY MAINTENANCE AFTER LANDING. THE REPORTER ALSO STATES THAT THEY HAD NUMEROUS OTHER EICAS MESSAGES DURING THE DESCENT THAT SEEMED TO APPEAR AND DISAPPEAR WHEN THE HF TRANSMIT SWITCH WAS PRESSED. HE DOES NOT KNOW HOW THIS ISSUE WAS RESOLVED.