Fault Codes/Rehlko/AUX SWITCH OPENRehlkoAUX SWITCH OPENUnclassifiedTransfer SwitchWhat This Code MeansATS is in neither position; All inputs are openPossible Causes•Main shaft auxiliary switches openRelated Rehlko Fault CodesAUXILIARYSWITCHOPENBUSLIVEDEADATS FAIL XFRCHECK ATS COMERRORATS COMERRORCHECK MODULE SETUP TO CLEAR FAULTATSCONTACTOROKFFAIL TO OPEN SOURCE1FAIL TO OPEN SOURCE2FORCEDTRANSTOOFFBrowse all Rehlko fault codes→ASK RUDY ABOUT THIS FAULTGet a diagnosis walkthrough for AUX SWITCH OPEN on your specific Rehlko unit — cited to the OEM manual, not a forum guess.Your question about AUX SWITCH OPENGET THE ANSWERFree account required — we'll bring your question with you.