ELECTRICAL EQUIPMENT - Q.2 4. Fault Finding on AC5 The  AC  5  alternator  is  so  designed  that  a  flow  of current   indicated   either   by   the   extinguishing   of   the warning  light,  or  as  shown  on  the  ammeter,  is  sufficient evidence   that   the   system   is   in   proper   working   order. Therefore,   no   open   circuit,   voltage   or   current   output checks should be performed on the installation UNLESS:— (a)   The    warning    light    fails    to    illuminate    when    the generator  is  stationary,  and  the  switch  is  closed  OR fails  to  become  extinguished  when  the  alternator  is running. (b)   No charging current is shown on ammeter. (c)   The battery is flat. (d)   The   battery   is   "boiling",   indicating   loss   of   voltage control. If  any  of  the  above  symptoms  occur,  the  procedure indicated below should be followed. (a)   Connect  a  good  quality  moving  coil  voltmeter  0-50 volts  range  across  the  battery  or  regulator  negative terminal,   and   one   of   the   three   positive   terminals marked  LO,  MED,  HI.    Disconnect  alternator  output terminal.    Fit  a  good  quality  moving  coil  0-100  amp ammeter  in  series  with  the  alternator  terminal  and output  lead.    The  battery  should  be  in  a  charged condition. (b)   Close the warning light switch (master electric switch on  dashboard)  when  the  warning  lamp  should  light up. (c)   Switch   on   a   10-15   amperes   load   such   as   lights, fans, etc., for fifteen minutes. (d)   Start engine and run at fast idle speed when 1. The warning light should go out. 2. The    ammeter    records    a    small    charge    dc- pendant on engine speed. (e)   Increase   engine   speed   momentarily   to   maximum speed,  when  the  charging  current  should  be  about 30 Amperes for 24 Volt,  and 53 Amperes for 12 volt systems. (f) With   the   alternator   running   at   approximately   half speed,  (engine  speed  about  1.500)  rev/min)  switch off   electrical   load.      Depending   on   the   connection selected  for  the  positive  sensing  wire  LO,  MED  or HI,  the  voltage  should  rise  to  between  26  and  28 volts  on  24  volt  systems  and  13-14  volts  on  12  volt systems  and  then  remain  constant.    At  the  same time the current reading should drop appreciably. Any variance in the above data could indicate a fault and  the  following  procedure  should  be  adopted  before disconnecting any components. The  regulator  is  a  sealed  unit  and  is  non-repairable and if found to be faulty it must be replaced. Warning   Lamp   does   not   light   up   when   switched "On". Check the bulb. If no fault Check  all  wiring  connections  at  regulator,  alternator and battery. If no fault Switch   off,   disconnect   “F”   lead   at   regulator   and connect it to the negative terminal. Switch on.  If warning lamp lights up, the regulator is faulty.  If lamp fails to light up, the alternator is faulty. Warning Lamp does not go out and Ammeter shows no output when running. Check all regulator, alternator and battery connections. If no fault Switch   off,   disconnect   “F”   lead   at   regulator   and connect to regulator negative terminal. Switch on, and run at fast idle. If no output,  alternator is faulty. If output appears, regulator is faulty. Warning  Lamp  does  not  go  out  when  running  and Ammeter shows reduced output with full output only at  maximum  speed  or  Warning  Lamp  goes  out  but Alternator delivers reduced output.  Full output only at maximum speed. Alternator   faulty.        Remove    from    installation    and apply open circuit diode check. Warning  Lamp  flashes  intermittently  and  Ammeter needle  oscillates  when  Battery  is  fully  charged  and no loads are switched in. Check for excessive resistance in regulator negative sensing lead. If no fault, regulator is faulty.