TM 9--2350--292--20--1 0187 00--147 0187 00 PREVENTIVE MAINTENANCE CHECKS AND SERVICES INCLUDING LUBRICATION INSTRUCTIONS -- CONTINUED TABLE 3 PREVENTIVE MAINTENANCE CHECKS AND SERVICES INCLUDING LUBRICATION INSTRUCTIONS, SEMIANNUALLY -- CONTINUED ITEM NO. NOT FULLY MISSION CAPABLE IF: PROCEDURE LOCATION ITEM TO CHECK/ SERVICE INTERVAL SEMIANNUALLY EXTERIOR 56 Auxiliary Power Unit (HATZ) -- Continued c.  Replace primary fuel filter (4) (WP 0609 00). d. Replace secondary fuel filter (5) (WP 0609 00). Any fuel leaks. e. Remove bottom cap (6) of fuel/water separator (7) then remove and replace fuel/water separator filter element (8) and install bottom cap (6). f.   Tighten  fuel  and  oil  connections  that leak. g. Inspect air system components; replace if damaged or deteriorated. h. Service air cleaner. Check for cleanliness and obstructions. Replace filter if damaged (WP 0608 00)). Clean if dirty (TM 9--2350--292--10). i.   Start APU engine (TM 9--2350--292--10). Listen for unusual noises in engine and generator which might indicate improper operation. j.   Observe warning lights and oil pressure gauge to see if unit is functioning properly (TM 9--2350--292--10). Oil pressure gauge should indicate approximately 55 to 80 psi (368 to 551 kPa). Shut off engine. k. Remove adhesive from thermostatic switch S1 (9). Using a jumper wire, short the terminals of thermostatic switch S1 (9) and observe the sump fan operation. Apply adhesive (item 25, WP 0716 00) to exposed terminals of switch S1 (9). l.   Remove adhesive from thermostatic switch S2 (10). Using a jumper wire, short the terminals of thermostatic switch S2 (10) and observe the door fan operation. Apply adhesive (item 25, WP 0716 00) to exposed terminals of switch S2 (10). 9 10 EMERGENCY FUEL SHUT-- OFF PRIMARY  SECONDARY FUEL FILTERS AUX. POWER UNIT 5 4 6 8 7 Dirty or obstructed air cleaner. Any unusual noises. Malfunctioning lights or low pressure. Door fan or sump fan does not operate.