TM 5-6115-640-14&P Table 4-1.  Unit Preventive Maintenance Checks and Services - Continued H - Hours of operation W - Weekly M - Monthly S - Semiannually (As indicated) (40 hours) (100 hours) (500 hours) INTERVAL ITEM Item to be inspected Procedures NO. H W M S 6 300 Batteries Perform a hydrometer test on batteries every 300 hours, or quarterly.  Refer to TM 5-6115-615-12 for test procedures. 7 100 Dust Valves on Air Cleaner Clean out dust valve on air cleaner assembly every 100 operating hours (more fre- quently under unusual con- tions). 8 1000 Air Cleaner Clean every 1000 operating hours or as conditions dictate.  Replace air cleaner every 2000 opera- ting hours. 9 Taillights Inspect for broken or cracked lenses or defective bulbs.  Replace if neces- sary. 10 Intervehicular Cable Check for cuts, breaks, frayed wires, or damaged plug. 11 Drawbar Ring Check security for mount- ing.  Inspect ring for excessive wear. 12 Safety Chains Inspect for broken links or missing chain(s). 13 Reflectors Inspect for any cracked, broken, or missing reflec- tors.  Replace if neces- sary. 4-15