THE 9TH MAG HYADES 12.52-HR ECLIPSING BINARY (EB) V471 TAURI (BD +16 516) HAS BEEN INTENSELY STUDIED AT NEARLY ALL WAVELENGTHS SINCE ITS DISCOVERY BY NELSON&YOUNG (1970). FEW CLOSE BINARIES OFFER MORE FUNDAMENTAL INSIGHTS INTO THEIR EVOLUTIONARY HISTORY THAN V471 TAURI. V471 TAU CONSISTS OF A ROCHE-LOBE DETACHED CHROMO-SPHERICALLY-ACTIVE K2V STAR AND A HOT (~35 000K) DAZ WHITE DWARF (WD) (E.G. GUINAN&SION 1984 SION ET AL. 2012 VACCARO ET AL. 2015). V471 TAU IS A DESCENDANT OF COMMON ENVELOPE (CE) EVOLUTION IN WHICH THE PRIMARY COMPONENT (THE PRESENT WD) OF THE WIDE BINARY EVOLVED TO AN ASYMPTOTIC BRANCH GIANT LEADING TO THE SPIRALING IN OF ITS COOL DWARF SECONDARY WITH EVENTUAL EJECTION OF THE COMMON ENVELOP. V471 TAU IS THE ONE OF NEAREST EXAMPLES OF A POST-CE (PCE) / PRE-CV SYSTEM. SURPRISINGLY PERIODIC 9.25 MIN (~555-SEC) X-RAY VARIATIONS WERE DISCOVERED BY JENSEN ET AL. (1986) WITH EXOSAT. THIS PERIODICITY WAS SUBSEQUENTLY CONFIRMED WITH ADDITIONAL X-RAY UV&U OBSERVATIONS (SEE CLEMENS ET AL. 1992 SION ET AL. 2012). THE 9.25 MIN MODULATED VARIATIONS ARE THEORIZED TO ARISE FROM THE ROTATION PERIOD OF THE WD AND ORIGINATE FROM ACCRETING WINDS ONTO THE TILTED MAGNETIC POLES OF THE STAR. SUBSEQUENT STUDIES HAVE SHOWN THAT THE 9.25-MIN UV AND X-RAY VARIATIONS ARE ~180-DEG OUT OF PHASE. CLEMENS ET AL. 1992 AND SION ET AL. 2012 SUGGEST THE MAGNETIC POLES OF THE SPINNING WD APPEAR RELATIVELY DARK AT X-RAYS (DUE TO THE HIGHER OPACITY OF METALS IN THE ACCRETING GAS) AND BRIGHT IN THE UV (DUE TO ACCRETION HEATING/ENERGY FROM THE K-STAR STELLAR WIND). NICER S CAPABILITIES WILL ALLOW THESE VARIATIONS TO BE OBSERVED WITH AN EXCELLENT COMBINATION OF S/N AND TEMPORAL RESOLUTION. WE RECENTLY COMPLETED A DETAILED ANALYSIS OF OVER 45-YEARS OF V471 TAU ECLIPSE TIMINGS (MARCHIONI ET AL. 2018). THE ANALYSIS OF THE OBSERVED MINUS COMPUTED TIMES (O-C S) SHOW A WELL-DEFINED 35.2-YR PERIODIC (NEAR-SINUSOIDAL) PERIODICITY (SEE FIG.3). THIS SMALL GRAVITATIONAL PULL WAS MODELLED BY A SUB-STELLAR TERTIARY BODY WITH M SIN I = 0.043 M. P = 35.2 YRS A = 13.6 AU&E = 0.1. OUR STUDY ALSO SHOWS EVIDENCE OF A 9.7+/-1.6 YR (LIGHT SEMI-AMPLITUDE ~20S) PERIOD POSSIBLY FROM THE KEPLERIAN LTTE FROM A LARGE JUPITER-SIZE 4TH BODY. BUT THIS IS LESS CERTAIN. OBJECTIVES: (1) WE WILL CAPITALIZE ON NICER S UNIQUE CAPABILITIES TO SECURE RAPID HIGH-S/N X-RAY MEASURES OF THE TARGET. THIS IS CRUCIAL TO DETAIL THE SPIN PHASE RESOLVED X-RAY FLUXES OF THE MAGNETIC WD AND TO ISOLATE&STUDY FLARES FROM THE K-STAR WHICH THE K2 SATELLITE HAS SHOWN OCCUR FREQUENTLY. WE WILL ALSO SEARCH FOR ANY EFFECT THAT FLARES (AND THE ENHANCED WINDS) HAVE ON THE WD ACCRETION. THE RESULTING XRAY CURVE WILL BE MODELED TO TEST AND CHARACTERIZE THE STELLAR WIND ACCRETION HYPOTHESIS&CONFIRM/DENY THE PRESENCE OF THE BROWN DWARF USING THE 9.25 MIN ROTATION TIMINGS OF THE WD. (2) OUR ANALYSIS OF X-RAY DATA FROM 1980-2015 INDICATES A POSSIBLE ~15.5-YR ACTIVITY CYCLE (SEE FIG. 4). THE REQUESTED NICER OBSERVATIONS WILL YIELD FRESH LX MEASURES THAT WILL TEST THIS POSSIBLE CYCLE. OUR ANALYSIS PREDICTS AN LX MAXIMUM DURING 2019-2020. (3) PERIOD ANALYSIS OF THE NICER DATA WILL YIELD AN INDEPENDENT MEASURE OF THE WD ROTATION RATE. THIS WILL BE COMPARED WITH PREVIOUS ROTATION PERIOD DETERMINATIONS GOING BACK TO 1985 TO SEARCH FOR PERIOD CHANGES FROM THE ACCRETION PROCESSES. WE HAVE USED PRIOR CHANDRA ACIS X-RAY DATA TO MEASURE THE ROTATION PERIOD IN 2002 AND FIND THAT THE PERIOD IS SLIGHTLY SHORTER THAN THE PERIOD MEASURED FROM THE 1985 EXOSAT DATA. THE NICER OBSERVATIONS WILL EXTEND THE TIME BASELINE. (4) AS DONE BY VANDERBOSCH ET AL. 2017 WE WILL USE THE ROTATION OF THE WD AS AN INDEPENDENT CLOCK TO MEASURE AND TEST GRAVITATIONAL EFFECTS ON THE EB BARYCENTER BY THE BROWN DWARF THAT IS INDICATED FROM THE LTTE ANALYSIS OF 45-YRS OF EB ECLIPSE TIMINGS. THE ANALYSIS OF ECLIPSING TIMINGS SHOWS A WELL-DEFINED 35.3-YR PERIODIC OBSERVATIONS OF O-CS FIT BY THE LTTE OF A BROWN DWARF.