TM 9-4940-342-14&P Table 5-1.  Troubleshooting - Continued Malfunction Probable cause Corrective action 10.  Low operating tem- perature - Continued d.  Scale buildup in cod - Continued pressure   gage   and   outlet   pressure gage exceeds 100 psi unit should be descaled. e.  Soot buildup in coil. e.  Inspect coil and remove burner and heater shell hat. Wash soot off coil. f.   Combustion air adjusted incorrectly. f.   See malfunction 3, step h. g.  Copper tube lines or regulator are leaking or cracked. g.  Locate  and  repair  leaks  or  replace lines. h.  Improper venting of combustion chamber (excessive wind). h.  Check for excessive downdraft vent stack restriction. 11.  Excessive smoke in burner exhaust. a.  Combustion air adjusted in- correctly. a.  See malfunction 3, step h. b. Blower inlet dirty or obstructed, or dirty blower. b.  Inspect blower inlet. Clean inlet and remove obstruction. Clean blower. c.  Incorrect blower rotation. c.  See malfunction 3, step f. d.  Dirty fuel strainer. d.  See malfunction 6, step d. e.  Water in fuel. e.  See malfunction 8, step k. f.   Dirty or worn burner nozzles. f.   See malfunction 8, step g. g.  Improper fuel being used. g.  Use  only  fuels  having  30-38  API rating. h.  Excessive soot buildup in coil or combustion chamber. h.  See malfunction 10, step e. 12.  Unit operates rough, coil hammers and vibrates. a.  Air dome needs draining. a.  Coil outlet and back pressure gages pulsate.   Drain   air   dome   every   4 hours.   (see   daily   maintenance   in- structions.) b.  Back pressure in heating coils excessive (scale buildup). b.  Coil outlet and back pressure gages pulsate.  Run  back  pressure  check. Descale unit. c.  Faulty bearings in water pump. c.  Coil outlet and back pressure gages pulsate. See malfunction 9, step h. d.  Pump and motor belts are slipping. d.  Refer     to     belt     adjustment     and tighten  in  accordance  with  recom- mendations. Section III. GENERAL MAINTENANCE 5-4. Maintenance and Adjustments 5-5. General This   section   provides   the   procedures   for   main- tenance  and  adjustments  that  are  required  to  keep the steam cleaner operating properly. 5-6. Coil Descaling Procedure (Acid Washing) a.  Under    all    operating    conditions,    natural mineral  deposits  in  water  will  form  scale  deposits within the heating coils, requiring periodic removal. b.  The  descaling  procedure  is  accomplished  as follows: (1)  Remove  nozzle  from  cleaning  gun.  Turn off water supply to cleaner and close soap solution metering valve. (2)  Disconnect  coil  inlet  hose  (water  supply hose   from   water   pump   to   air   dome   inlet   pipe assembly)  and  attach  auxiliary  descale  pump  and tank.  (Not  required  when  using  unit  water  supply tank.) CAUTION For extremely frequent descaling, it is advisable to use auxiliary descale pump and tank. (3)  Fill auxiliary or unit tank 1/3 full of water and affix cleaning gun in a manner that, with descale pump in operation, water is circulating from descale tank  through  heating  coil,  steam  hose  and  cleaning gun back to descale tank. (4)    Be  sure  there  is  adequate  water  level  in descale    tank    to    maintain    acid    pump    prime. Returning water is filtered through the screening to avoid  recirculating  scale  chips  during  acid  wash procedure. 33