TM  10-3930-638-24&P 2 - 1 2 .    C O O L I N G    S Y S T E M    T R O U B L E S H O O T I N G    ( c o n t) MALFUNCTION TEST  OR  INSPECTION CORRECTIVE ACTION 3. COOLING SYSTEM NOT PRESSURIZED (cont) Step 2. (cont) a. If pressure drops quickly, radiator has serious leakage. Replace radiator (para 2-17c). b. If pressure holds steady for two or more minutes, radiator check is satisfactory c. If pressure drops slowly, radiator has seepage or slight leakage. Replace radiator (para 2-17c). 2 - 1 3 .     G A G E S     T R O U B L E S H O O T I NG MALFUNCTION TEST  OR  INSPECTION CORRECTIVE ACTION 1. ENGINE OIL PRESSURE GAGE DOES NOT INDICATE CORRECT PRESSURE Step  1. Place IGNITION switch in ON position. Oil pressure gage should indicate zero. a. If zero indication not obtained, proceed to step 2. b. If zero indication obtained, proceed to step 3. Step  2.  Disconnect  wire  from  oil  pressure  sender. Oil  pressure  gage  should  indicate  zero. a. If oil pressure gage indicates 80 (full scale), repair or replace short circuited wire between oil pressure sender and oil pressure gage. b.  If  oil  pressure  gage  indicates  zero,  replace  oil  pressure  sender. c. If oil pressure gage indicates other than zero or 80 (full scale), replace oil pressure gage. Step  3. Temporarily  connect  jumper  wire  between  oil  pressure  gage  SENDER  terminal  and  chassis  ground. Place IGNITION switch in ON position. Oil  pressure  gage  should  indicate  80  (full  scale). a. If 80 (full scale) indication not obtained, proceed to step 4. b. If 80 (full scale) indication obtained, disconnect wire and proceed to step 5. Step 4. Check for +24 Vdc between oil pressure gage IGN terminal and ground (IGNITION switch in ON position). a. If +24 Vdc not obtained, troubleshoot electrical system (para 2-19). b. If +24 Vdc obtained, disconnect jumper wire between oil pressure gage SENDER terminal and ground,  and  replace  oil  pressure  gage  (para  2-18b). 2-27