C340 PLT HAD AN ALT AND TRACK DEV WHILE ATTEMPTING THE VOR RWY 26L APCH TO ELP.

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ON DEC/WED/03; ACFT X; A CESSNA 340; DEPARTED CORPUS CHRISTI; TX (CRP) AT APPROX XA15 HRS FOR EL PASO; TX (ELP). A DUATS BRIEFING WAS OBTAINED. THE DEP AND ENRTE PORTIONS OF THE FLT WERE UNREMARKABLE. AFTER HDOF FROM ZAB TO ELP APCH; APCH VECTORED ACFT X FIRST TO THE S AND THEN TO THE N OF THE VOR 081 DEG RADIAL FOR TFC. THIS WAS A VOR APCH TO RWY 26L AND WAS INITIALLY FLOWN WITH THE AUTOPLT ON IN THE HEADING MODE WITH ALT HOLD ENGAGED. ABOUT 12-15 MI E OF THE VOR AT 6500 FT; ACFT X WAS CLRED FOR THE APCH AND INSTRUCTED TO TRACK THE 081 DEG RADIAL INBOUND. WX AT THE TIME WAS CLR OF IMMEDIATE CLOUDS (BASES ABOUT 8500 FT MSL) BUT FORWARD VISIBILITY WAS LIMITED; ALTHOUGH THE GND WAS VISIBLE IN DUSK TO DARK TRANSITION LIGHTING WITH MODERATE TURB AND RELATIVELY HIGH WINDS AND BLOWING DUST. CLOSE TO INTERCEPTING THE 081 DEG RADIAL; THE PLT'S ATTN WAS DIVERTED BY A SMELL IN THE COCKPIT NOT UNLIKE AN ELECTRICAL OVERHEAT. HOWEVER; THERE WAS NO FIRE OR SMOKE. THE PLT'S ATTN WAS DIVERTED AND THE ACFT CROSSED S OF THE 081 DEG RADIAL BY A 4 DOT DEFLECTION OF THE VOR. THE PLT CAUGHT THE TRACKING ERROR AND PROCEEDED N TO REINTERCEPT THE 081 DEG RADIAL. ABOUT 1 MIN LATER; WHEN THE ACFT WAS ABOUT 2.2 MI FROM THE VOR; ATC FIRST ADVISED OF THE TRACKING ERROR AND CANCELED THE APCH CLRNC AND THEN ALMOST IMMEDIATELY REINSTATED IT AS THE ACFT WAS APCHING THE 081 DEG RADIAL. COMPOUNDING THE PROB; THE TWR ISSUED A LOW ALT ALERT AS THE ACFT HAD DSNDED BELOW 5400 FT TO ABOUT 5000 FT; BTWN GIFEN INTXN AND THE VOR. THE PLT IMMEDIATELY DISCONNECTED THE AUTOPLT AND CLBED TO 5400 FT AND THE REST OF THE APCH WAS UNREMARKABLE. DURING THIS TIME; THE ACFT WAS MOSTLY CLR OF CLOUDS AND GND LIGHTS WERE VISIBLE. CONTRIBUTING FACTORS: SMELL OF AN ELECTRICAL PROB IN THE COCKPIT DIVERTING THE PLT'S ATTN DURING A CRITICAL PHASE OF FLT; AUTOPLT ALT HOLD MALFUNCTIONED WHEN APCH FLAPS WERE LOWERED; PLT'S FAILURE TO MORE ACCURATELY MONITOR THE APCH COURSE AND ALT WHILE CHKING FOR ELECTRICAL PROBS. CORRECTIVE ACTION: PLT WILL REVIEW CRM PROCS AND WILL FLY MORE INST APCHS TO SHARPEN HIS SKILLS BOTH IN A SIMULATOR AND IN THE ACFT.