SECTION Q Alternator, Dynamo and Starter Motor ALTERNATOR Models AC5 and 11AC 1. General At    the    time    of    writing    there    are    two    types    of alternator supplied with the 4.236 marine engine, namely the  AC  5  with  its  associated  440  regulator,  and  the  11 AC with the 4 TR Control Box. These are driven by the engine in the same manner as   a   D.C.   Generator,   namely,   belt   driven   from   the crankshaft pulley, but the advantage lies in their ability to provide higher maximum output at lower speeds, to cope with   increased   electrical   load   demanded   by   modem equipment.  They are also much lighter in weight, output for output. As   opposed   to   the   DC    Generator    in    which    the armature windings rotate inside a stationary field system, the    alternator    has    a    rotating    field    system    inside   a stationary  generating  winding.    When  the  rotor  rotates inside   the   stator,   the   output   produced   is   alternating current (AC).  This is unsuitable for charging the battery which  requires  direct  current  (DC),  so  it  is  rectified  by means of diodes which converts it to uni-directional flow to the battery. The   alternator   voltage   output   is   maintained   within close   limits   by   means   of   a   control   box   which   is   fully transistorized and functions as fast switches. 2. Precautions As  previously  described  the  diodes  in  the  alternator function  as  one-way  valves  and  the  transistors  in  the regulator/control box operate as fast switches.  Both are accurate and sensitive. They     do     not     wear     out     and     seldom     require adjustment,  but  because  they  are  sensitive  to  voltage changes  and  high  temperature,  the  precautions  are  vital to prevent them from being destroyed. (a)   DO NOT disconnect the battery whilst  the  engine  is running.      This   will   cause   a   voltage   surge   in   the alternator  charging  system  that  will  immediately  ruin the diodes or transistors. (b)   DO NOT disconnect a lead without first stopping the engine  and  turning  all  electrical  switches  to  the  off position. (c)   DO NOT cause a short circuit by connecting leads to incorrect   terminals.      Always   identify   a   lead   to   its correct terminal.  A short circuit or wrong connection giving reverse polarity will immediately and permanently ruin transistors or diodes. (d)   DO  NOT  connect  a  battery  into  the  system  without checking for correct polarity and voltage. (e)   DO   NOT   "flash"   connections   to   check   for   current flow.  No matter how brief the contact the transistors may be ruined. 3. Maintenance The alternator  charging  system  will  normally  require very little attention, but it should be kept free from build- up of dirt, and a check made if it fails to keep the battery charged. (a)   Regularly   inspect   the   driving   belts   for   wear   and correct   tension.      It   is   important   to   ensure   that   all belts on a multiple belt drive have equal tension and are each carrying their share of the load.  Slack belts will  wear  rapidly  and  cause  slip  which  will  not  drive the   alternator   at   the   required   speed.      Drive   belts which are too tight impose severe side thrust on the alternator bearings and shorten their life. Periodically   ensure   that   the   alternator   is   correctly aligned to the drive. (b)   Do not replace faulty belts individually in a multi-belt system.  A complete matched set of drive belts must always be used. (c)   Keep  the  alternator  clean  with  a  cloth  moistened  in kerosene  or  cleaning  fluids.    Ensure  that  ventilation slots and air spaces are clear and unobstructed. (d)   Remove any dirt accumulated on the regulator/control    box    housing,    and    ensure    that cooling air can pass freely over the casing.