TM 10-3930-671-24 Alternator Maintenance Precautions WARNING • Disconnect the battery, before connecting or disconnecting test instruments (except voltmeter) or before  removing  or  replacing  any  unit or    wiring.    Accidental    grounding    or shorting   at   the   regulator,   alternator, ammeter   or   accessories,   will   cause severe   damage   to   the   units   and/or wiring and possible injury to personnel. • If a booster battery or a fast charger is used,  its  polarity  must  be  connected correctly   to   prevent   damage   to   the electrical system components. Connect  positive  to  positive,  negative to   negative.      Connect   the   negative cable  ground  connection  last  (but  not to   the   battery   because   an   explosion could result). CAUTION • The     field     circuit     must     never     be grounded on this system, between  the alternator and the regulator. Grounding of the field terminal either at the alternator or regulator  will  damage the regulator. • Do   not   ground   the   output   terminal. Grounding    of    the    alternator    output terminal   may   damage   the   alternator and/or circuit and components. • Do not connect battery to the regulator field     terminal     or     damage     to     the regulator will result. • Do not attempt to polarize the altemator.  No  polarization  is  required. Any   attempt   to   do   so   may   result   in damage  to  the  alternator,  regulator,  or circuits. • Be sure the alternator and battery have the   same   ground   polarity.      Battery polarity    should    be    checked    with    a voltmeter before connecting the battery.  Reversed battery connections may   damage   the   rectifiers,   wiring   or other    components    of    the    charging system. NOTE • Do  not  short  across  or  ground  any  of the terminals on the alternator or in the charging  circuit,  except  as  specifically instructed in a troubleshooting procedure. • The alternator must not be operated on open   circuit   with   the   rotor   winding energized.  Check all terminals for tight connections. Alternator Inspection 1. Inspect   the   terminals   for   corrosion   and   loose connections. 2. Inspect wiring for damaged or worn insulation. 3. Check mounting bolts for tightness. 4. Check  the  alternator  drive  belt  for  wear,  correct alignment and correct tension. NOTE When servicing the charging system, never  remove  a  unit  until  tests  have shown it to be defective. Troubleshooting Procedures NOTE Following   these   procedures   in   the order    presented    will    lead    to    the location  and  correction  of  charging system defects in the shortest possible time.  Usually only a portion of  these  procedures  will  need  to  be performed.  It will never be necessary to perform all the procedures in order to locate the trouble. Figure 1. 1. A  basic  wiring  diagram  showing  charging  circuit connections is shown in Figure 1. Refer to Section 6.1, Electrical System Wiring, for additional information. Figure 2. F-262