Quantcast CHECKING THE 120 VOLT AC STARTER MOTOR

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TM 5-4240-501-14&P STARTERS Gear Drive 12V & 120V Insert  the  tachometer  in  the  end  of   the   starter   motor shaft  and  activate  the  starter  motor.    A  starter  motor  in good condition will be within the following specifications. 1. Starter motor RPM - 5,600 minimum. 2. Current - 6 amperes maximum (disregard surge current) CHECKING THE 120 VOLT AC STARTER MOTOR A performance test of the 120 volt starter motor may be made in the following manner. Equipment Needed - 1. A tachometer capable of reading 10,000 RPM. 2. An  ammeter  capable  of  reading  0  to  10  amperes AC (RMS). DANGER:  The  performance  test  of  this  starter  requires the  use  of  an  ammeter,  connected  in  the  120  volt  AC starter  motor  circuit.    Extreme  care  should  be  used  in making   this   test   to   minimize   the   hazard   of   electrical shock. Clamp the starter motor in a vise as shown.  An ammeter may    be    connected    as    shown    in    the    accompanying illustration.  Fig.  73.  Plug the electrical cord into a 120 volt  outlet  and  insert  the  tachometer  in  the  end  of  the starter motor shaft. CAUTION:  Starter  motor  housing  contains  two  powerful ceramic   magnets   that   may   crack   if   motor   housing   is clamped  in  a  vise  or  struck  with  a  hammer  or  a  hard object. Fig.  73 - Checking 120 Volt Starter Motoi Performance A   starter   motor   in   good   condition   will   be   within   the following specifications. 1. Starter Motor RPM - 8,300 minimum. 2. Current -- 1/2 amperes maximum AC. If either the 120 volt AC or 12 volt DC starter motor does not    perform    satisfactorily,    the    following     should     be checked and corrected if necessary. 1. Binding condition between the pinion gear, helix and drive gear assembly. 2. Misalignment or binding between motor bearings. 3. Starter motor brushes sticking in brush holders. 4. Dirty or worn commutator. 5. Shorted, open or grounded armature. A.  Shorted armature (wire insulation worn and wires touching  one  another)  will  be  indicated  by  slow speed and high current. B.  Open armature (wire broken) will be indicated by low or no RPM. C.  Grounded   armature   (wire   insulation   worn   and wire  touching  armature  lamination  or  shaft)  will be indicated by excessive current or no RPM. 6. A defective starter motor switch (in cord). 7. A defective starter motor rectifier assembly. 8. Weakened magnets. DISASSEMBLY OF STARTER MOTOR Study Fig.  69 prior to starter motor disassembly. NOTE:  END  HEAD,  END  CAP  AND  HOUSING  MUST BE   PLACED   IN   THE   SAME   POSITION   AS   WHEN REMOVED,  OR  INTERFERENCE  MAY  RESULT.    See Fig.  74. Fig.  74 - Match Marks Remove thru bolts.  Fig.  75.  The end cap may then be removed. (See  checking  starter  motor  drive  if  repair,  cleaning  or replacement of drive assembly is necessary.) 20


 


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