TM 5-41-287-15 1 Microswitch S101 13 Electrical connector plug P109 2 Condenser fan motor B10 14 Thru-bulkhead electrical connector J107-J109 3 Voltage conversion connector P111 15 Electrical tray assembly 4 Low ambient switch S102 16 Fuse holder and fuse F1 5 High-low pressure switch S103 17 Electrical connector jack J101 6 Terminal board TB-1 18 Electrical connector jack J102 7 Evaporator blower motor R102 19 Thru-bulkhead electrical connector J106-JL108 8 Compressor motor R10 20 Electrical connector plug P108 9 Solenoid valve coil L101 21 Electrical connector plug P104 10 Voltage conversion connector P110 22 Electrical connection jack J104 11 Electrical connector plug P111 23 Heater bank (2) 12 Thru-bulkhead electrical connector J105J113 24 Heater temperature switch S104 Figure 6-2. Continued (5) Reconnect wires 109 and 111 to ter- minal board TB1. c. High-low Pressure Switch (S103). Isolate leads 110 and 112 from Terminal Board TB1; and check for continuity. If con- tinuity exists replace switch. There is no practical method for checking high-low pres- sure switch operation in the air conditioner under operating conditions. It is recommended that a suspected high-low pressure swi’cbh be replaced. d. Heater Temperature Switch (Si04). Using a multimeter, check heater temperature switch S104 as follows: (1) Remove power input plug. (2) Connect the multimeter test leads between J112-B and J112-D terminals. (3) Check to determine that heater tem- perature switch is closed. (4) Disconnect P107 from J107. (5) Place a thermometer  thru  condi- tioned air outlet screen so that thermometer bulb is near heater temperature switch. (6) Connect power supply plug to Input Power receptacle J101. (7) Start air conditioner. Set air condi- tioning switch to HEAT position; then turn temperature control rheostat dial clockwise to WARM position. (8) Observe that heater temperature switch opens when thermometer reads 126  t 5°F and closes when temperature falls to 105 +5°F. (9) If heater temperature switch does not open at 125 + 5°F and close at 105 ± 50F, the switch is defective and must be replaced. (10)  Remove multitester test leads, con- nect P107 to J107 and remove thermometer. 6-5 e. Thermostat (S105). Using a multimeter check thermostat S105 as follows: (1) Remove thermostat  S105,  (para 3-39) leaving thermostat leads attached to terminal board TB1. (2) Connect multimeter test leads to terminal board TB2 contacts I and 2. (3) Run air conditioner with air condi- tioning switch in HEAT position and temper- ature control switch set to maximum WARM position. (4) Set thermostat bulb in water having a temperature of 40 + 5°F. Determine that heaters are operating and that multimeter indicates continuity between TB2 control 1 and 3. (5) Set thermostat bulb in water having a temperature of 105 + 10°F; then set tem- perature control switch to maximum COOL position. Determine that heaters deenergize and that multimeter indicates an open circuit between TB2 contacts 1 and 3. (6) Set the air conditioning switch to COOL position. (7) Immerse thermostat bulb in water having a temperature of 40 + 50F. (8) Rotate temperature control switch to maximum WARM position and note that mul- timeter indicates an open circuit across TB2 contacts 1 and 3. Also note that refrigerant ceases to flow through refrigerant liquid sight indicator. (9) Set master circuit breaker to OFF position and disconnect power input plug from J101.