TM 9-2320-360-20-1 WARNING Jewelry can catch on equipment and cause injury or short across electrical circuit and cause severe burns or electrical shock.  Remove rings, bracelets, watches, necklaces, and any other jewelry before working around HET Tractor. WIRE NO. 1676 VOLTAGE TEST (1) Turn ENGINE switch to ON position. (2) Place positive (+) probe of multimeter on wire no. 1676 at TRAILER B O.  TAIL relay. (3) Place negative (-) probe of multimeter on ground and look for 10-14 volts on multimeter. (4) Turn ENGINE switch to OFF position. WIRE NO. 1680 VOLTAGE TEST (1) Turn ENGINE switch to ON position. (2) Place BLACK OUT LIGHTS switch in the on position. (3) Place BLACK OUT MARKER switch in the on position. (4) Place positive (+) probe of multimeter on wire no. 1680 at TRAILER B O.  TAIL relay. (5) Place negative (-) probe of multimeter on ground and look for 10-14 volts on multimeter. (6) Place BLACK OUT LIGHTS switch in the off position. (7) Place BLACK OUT MARKER switch in the off position. (8) Turn ENGINE switch to OFF position. Check ground wire no. 1435 from TRAILER B.O. TAIL relay for loose connections or damage. CONTINUITY TEST CAUTION Electrical power must be disconnected from circuit before continuity can be checked.  Failure to comply may result in damage to test equipment or electrical system. (1) Disconnect wiring from components at each end of wire. (2) Set multimeter to ohms position. NOTE A reading of infinity indicates an open circuit. (3) Connect multimeter leads to eachend of wire and check multimeter for continuity. NOTE Any reading besides infinity indicates a grounded wire. (4) Remove multimeter lead from one end of wire and connect to chassis ground. Change 2  2-571