Table 4-2. Troubleshooting-Continued Malfunction 7. Condenser air output volume low. 8. Air conditioner fails to heat. 9. Excessive noise. Probable  Cause Dirty   or   damaged   filter   or louvers. Iced or dirty evaporator coil. Defective evaporator fan. Defective  fan  motor. Evaporator fan speed switch set at low speed. Dirty condenser coil or guard. Defective   HIGH-LOW   con- denser fan thermostatic switch. Defective condenser fan. Defective fan motor. Air outlet Iouvers stuck in closed position. Selector   switch   improperly adjusted. Temperature control switch set incorrectly. Dirty evaporator return air filter. Defective evaporator fan motor. Defective  temperature  selector switch or mode selector switch. Defective heaters or wiring. Defective heater relay. Defective  heater  high  tem- perature cutout thermostatic switch. Evaporator  or  condenser  fan vibrating. Evaporator or condenser fan motor worn or defective. Compressor knocks or chatters. a. b. c. d. c. a. b. c. d. f. b. g. h. a. b. c. Clean or replace filter (para 4- 7). Clean or replace louvers as required  (para  4-18). De-ice and clean coil (para 4-24). Replace fan. Replace motor (para 4-38 and 4- 40). Reset switch to HIGH speed. Clean  coil  and  guard  (para  4-23). Replace switch (para 4-41). Replace fan. Replace motor (para 4-38 and 4- 40). Free louvers and control cable. Adjust  control  or  refer  to  direct support maintenance if actuating cylinder   is   not   functioning properly. Reset selector switch to LO-Heat or  HI-Heat  (para  2-10). Reset switch (para. 2-10). Clean fitter (para 4-17). Replace rnotor (para. 4-38 and 4- 40). Replace  defective  switch  (para  4- 44 through 4-48). Tighten connections and repair damaged wiring. Replace defective heaters (para 4-35). Replace defect relay ( para 4- 50 thru 4-54). Replace defective thermostatic switch  (para 4-34). Tighten fans on shafts. Tighten all mounting screws. Replace worn or defective motor (para 4-38 and 4-40). Stop  air  conditioner  and  report condition   to   direct   support maintenance. Section   VI. RADIO   INTERFERENCE   SUPPRESSION 4-13.   General   Methods   Used   to   Attain Proper   Suppression Essentially,  suppression  is  attained  by  providing  a low  resistance  path  to  ground  for  the  stray  currents. Methods   used   include   shielding   ignition   and   high frequency  wires,  grounding  the  frame  with  bonding straps  and  using  capacitors  and  resistors. 4-14.    Interference Suppression Components The   control   module,   junction   box   and   electrical system   components   are   grounded   to   the   housing. The  housing  is  connected  to  a  ground  wire  in  the power   supply.   Capacitors   (fig.   4-1)   are   located Corrective  Action across   the   rectifier   terminals.   Grommets   are   in- serted   in   the   heater   support   bracket   to   isolate heating  elements  from  bracket  to  prevent  metal  to metal   contact   and   scraping   during   expansion   and contraction   of   heating   elements.   Power   inlet   cover chains  are  encased  in  shrink  type  tubing  to  prevent rattling   of   chain   links. 4-15.   Replacement   of   Capacitor a.   Removal. (1)  Remove  front  top  cover  of  air  conditioner. (2)   Disconnect   capacitor   (fig.   4-1)   from terminals 1 and 3 or 2 and 4 of rectifier. 4-5