MD90 INCORRECTLY DISPATCHED WITH AN AUTO SPOILER PROB DEFERRED BY MAINT CTL. THE EQUIP PROB WAS NOT ASSESSED PROPERLY. ACFT RECALLED FOR MAINT ACTION. 'BOX' WAS CHANGED AND CIRCUIT BREAKERS RESET. PROB STILL EXISTED AFTER LNDG AT DEST ARPT. ACFT NEW TO AIRLINE.

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AFTER LNDG IN SLC; AN AUTOSPOILER FAULT LIGHT ILLUMINATED ON THE OVERHEAD ANNUNCIATOR PANEL. THE FAULT WAS WRITTEN UP AND MAINT THEN ELECTED TO DEFER THE ITEM. AFTER LOOKING UP THE PROB IN THE MEL; A PERFORMANCE PENALTY WAS NOTED. THE DISPATCHER WAS THEN CONTACTED AND ASKED ABOUT THE LEGALITY OF OPERATING INTO SNA WITH THIS PROB. THE DISPATCHER SAID ACFT COULD BE OPERATED INTO SNA. PLANE THEN DEPARTED FOR SNA. A MESSAGE WAS RECEIVED INFLT TO RETURN TO SLC; BECAUSE THERE WAS APPARENTLY A MISUNDERSTANDING BTWN MAINT AND THE DISPATCHER AS TO WHAT THE REAL PROB WAS AND THE PROPER PERFORMANCE PENALTY WAS NOT APPLIED INITIALLY. THEREFORE; THE ACFT WAS OVERWT FOR LNDG IN SNA. THE PROB WAS A REPEAT WRITE-UP; AND COULD BE CORRECTED BY FOLLOWING THE PROCS IN THE BOOK; WHICH CONSISTED OF RESETTING CIRCUIT BREAKERS FOR THE SYS. THE PROB WAS FIXED IN SLC AND REDISPATCHED FOR SNA. SUPPLEMENTAL INFO FROM ACN 379437: PROB RETURNED AFTER CLRING RWY. WAS OK FOR LNDG. FIXED WITH BOX CHANGE. WE COULDN'T FIND SNA IN ARPT SECTION OF ACFT RESTRS MANUAL. RETURN DECIDED BECAUSE OF LEGALITIES AND SAFETY CONSIDERATIONS.