TM 10-3930-659-34 2-17.  HEAT SHRINKABLE TUBING. Use heat shrinkable tubing (Item 56, Appendix B) to insulate soldered and crimped electrical connections as follows: (1) Cut desired length of new heat shrinkable tubing twice the diameter of the connection to be covered. (2) Slide heat shrinkable tubing onto the wire and out of the way before making electrical connection. (3) After making electrical connection, slide heat shrinkable tubing into place over electrical connection. WARNING DO NOT touch heat shrinkable tubing for at least 30 seconds after heating.  Heat shrinkable tubing is hot and will burn you. (4) Hold  heat  gun  (Item  35,  Appendix  E)  4-5  in.    (10.2-12.7  cm)  away  from  heat  shrinkable  tubing  and  apply heat  for  approximately  30  seconds.    Stop  applying  heat  as  soon  as  heat  shrinkable  tubing  forms  to  the  shape  of  the electrical connection. 2-18.  ELECTRICAL GROUND POINTS. Many electrical problems are the result of poor ground connections.  You can ensure that ground connections are good by performing the following steps: WARNING Although  battery  disconnect  switch  must  be  on  and  battery  ground  cable  connected  In  order  to  test electrical  circuit  voltage,  turn  off  battery  disconnect  switch  or  disconnect  battery  ground  cable  before performing resistance tests or replacing parts.  This will prevent shock to personnel, and damage to parts and equipment. (1) Remove hardware connecting ground cable terminal lug to ground point. WARNING Dry cleaning solvent, P-D-680, Is toxic and flammable.  Always wear protective goggles and gloves, and use  only  In  a  well-ventilated  area.    Avoid  contact  with  skin,  eyes,  and  clothes,  and  DO  NOT  breathe vapors.    DO  NOT  use  near  open  flame  or  excessive  heat.    The  solvent’s  flash  point  is  1000F-1380F (380C-590C).    If  you  become  dizzy  while  using  cleaning  solvent,  immediately  get  fresh  air  and  medical help. If solvent contacts eyes, immediately wash your eyes and get medical aid. (2) Clean mounting hardware, ground cable terminal lugs, and ground point with dry cleaning solvent (Item 47, Appendix B) and scrub brush (Item 5, Appendix B). (3)    Remove any rust with wire brush (Item 6, Appendix B) and crocus cloth (Item 8, Appendix B). 2-10