TM 9-2320-302-20 0010 00-15 Table 1. Electrical System Troubleshooting Procedures - Continued. MALFUNCTION TEST OR INSPECTION CORRECTIVE ACTION Radio Circuits Power  Source  for  24  VDC  Radio  Does  Not Operate. 1.    Check    24    VDC    25A    radio fuse. Replace 25A fuse if defective (WP 0071 00). 2.    Remove  24  VDC  25A  radio fuse.  Check  for  +24  VDC  at lead 421W fuse connector. If +24 VDC is present, go to step 3. If voltage is not present, repair lead  421W  to  24  VDC  constant power bus (WP 0119 00). 3.    Check  for  continuity  between ground lead and ground. If  continuity  is  indicated,  go  to step 4. If continuity is not indicated, repair ground lead (WP 0119 00). 4.    Check  for  +24  VDC  at  lead 421R from radio power source connector. If +24 VDC is not present, repair lead 421R (WP 0119 00). Instrument Wiring Circuits 1.  Instruments on Dashboard Do Not Operate. 1.    Check instruments 10A fuse. Replace 10A fuse if defective (WP 0071 00). 2.    Check for +12 VDC at ignition run power bus connector. If +12 VDC is present, repair lead 81C.   If   voltage   is   not   present, repair  connector  on  ignition  run power bus (WP  00119 00). 2.  Water Temperature Gage Does Not Operate. 1.    Disconnect    lead    81C    from water temperature gage. Check  for  +12  VDC  at  lead 81C. If +12 VDC is present, go to step 2. If voltage is not present, repair lead 81C (WP 0119 00). 2.    Disconnect  ground  lead  from water temperature gage. Check  for  continuity  between lead and ground. If continuity is present, go to step 3.  If  continuity  is  not  indicated, repair ground lead (WP 0119 00). 3.    Disconnect     lead     119     from water temperature gage. Check  for  +8  to  +12  VDC  at water temperature gage. If +8 to +12 VDC is present, go to step  4.  If  voltage  is  not  present, replace   water   temperature   gage (WP 0060 00). 4.    Disconnect     lead     119     from water temperature gage sensor.  Check  for  +8  to  +12 VDC at lead 119. If   +8   to   +12   VDC   is   present, replace   water   temperature   gage sensor (WP 0098 00). If voltage is not  present,  repair  lead  119  (WP 0119 00). 3.  Transmission Oil Temperature Gage Does Not Operate. 1.    Disconnect    lead    81C    from transmission   oil   temperature gage.  Check  for  +12  VDC  at lead 81C. If +12 VDC is present, go to step 2. If voltage is not present, repair lead 81C (WP 0119 00).