OPERATING ON AUTOPLT IN IMC -- DESPITE FAULTY ARTIFICIAL HORIZON. BE35 PLT GETS DISORIENTED; SUFFERS VERTIGO AND LOSS OF CTL DURING APCH. BREAKS OUT IN TIME TO SAFELY REORIENT THE ACFT AND BE VECTORED FOR A VISUAL APCH AND LNDG.

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HAD INDICATION THAT THE HORIZ ARTIFICIAL HORIZON GYRO WAS GOING BAD ENRTE FROM LHM. WOULD NOT HOLD ALT; SO JUST USED HDG BUG AND TRIMMED FOR ALT (CENTURY 2000/3 AXIS) ON-TOP MOST OF WAY WITH CLOUDS PARTING SO TOA WAS VISIBLE BEFORE BEING VECTORED TO THE COAST LINE FOR L DOWNWIND TO LGB RWY 30 ILS. SHOULD HAVE REQUESTED 'CONTACT' APCH AS THE CEILING AND VISIBILITY WERE OK FOR VFR EXCEPT THE 800 FT CEILING. ENTERED CLOUD AT 1600 FT HDG 120 DEGS. USE HDG BUT TO BASE TURN 030 DEGS AND INTERCEPT HDG OF 330 DEGS. ALT WENT NOSE UP RADICALLY SO TURNED OFF AUTOPLT AND LEVELED. LOC WAS FULL SCALE OFF BECAUSE NOT YET INTERCEPTED. SAW VFR TO THE R SO TURNED IMMEDIATELY TO SAFETY AS GAUGES WERE NO IMMEDIATE HELP. SHOULD HAVE CONTINUED STRAIGHT AHEAD WITH THE INTERCEPT HDG AND TALKED TO CTLR. INDUCED A FULL CASE OF VERTIGO SO WAS UNABLE TO NAV OR TALK -- JUST FLY BELOW THE CLOUDS. FINALLY REGAINED ORIENTATION WITH THE HELP OF CTLR TURNED 180 DEGS; INTERCEPTED VFR AND LANDED. GYRO HAD BEEN OVERHAULED. THIS WAS 5TH FAILURE. AVIONICS SHOP CONFIRMED GYRO BAD. GYRO OVERHAULED. OVERHAULED GYRO CHKS OK; BUT NOW AUTOPLT WILL NOT ENGAGE (SINCE INCIDENT) -- BEING CHKED.