Principles of Operation
There are 4 main principles involved with the basic theory of operation
- Heat transfer
- Latent heat of vaporization
- Relative humidity
- Effects of pressure
Normal Operation
Under normal operation, the air inlet door actuator motors are supplied voltage or ground on circuit 1116 (DG), depending on desired actuator rotation, by the electronic manual temperature control (EMTC) module. The EMTC module then supplies the appropriate voltage or ground to the other side of the actuator motor on circuit 1117 (LG).
Under normal operation, to rotate the mode door actuator clockwise, the EMTC module supplies voltage to the BLEND, DEFROST and FLOOR/PANEL mode door actuator motors through the door actuator feed B circuits, and supplies ground through the door actuator feed A circuits. To rotate the mode door actuator counterclockwise, the EMTC module reverses the voltage and ground circuits.
The mode door actuator feedback resistors are supplied a ground from the EMTC module by the mode door actuator return circuits and a 5-volt reference voltage on the mode door actuator reference circuits. The EMTC module reads the voltage on the mode door actuator feedback circuits to determine the mode door actuator position by the position of the actuator feedback resistor wiper arm.
Under normal operation, warm coolant flows from the engine through the heater core and back to the engine.
Under normal operation, when A/C is requested, a ground signal is sent to the smart junction box (SJB) through circuit 1397 (GY/RD) then a message is sent from the SJB through the CAN bus to the PCM. Voltage is provided to the A/C cycling switch through circuit 391 (RD/YE). The PCM receives input from the A/C cycling switch through circuit 420 (DB/YE) and (4.6L only) through the dual function pressure switch to circuit 198 (DG/OG).
The PCM provides a ground for the A/C clutch relay coil through circuit 321 (GY/WH). When the relay is activated, ignition voltage is supplied to the A/C clutch solenoid through circuit 883 (PK/LB). Ground is supplied for the A/C clutch through circuit 1205 (BK).
Under normal operation, when A/C is requested, a ground signal is sent to the smart junction box (SJB) through circuit 1397 (GY/RD) then a message is sent from the SJB through the CAN bus to the PCM. Voltage is provided to the A/C cycling switch through circuit 391 (RD/YE). The PCM receives input from the A/C cycling switch through circuit 420 (DB/YE) and (4.6L only) through the dual function pressure switch to circuit 198 (DG/OG).
The PCM provides a ground for the A/C clutch relay coil through circuit 321 (GY/WH). When the relay is activated, ignition voltage is supplied to the A/C clutch solenoid through circuit 883 (PK/LB). Ground is supplied for the A/C clutch through circuit 1205 (BK).
Under normal operation, the blower motor relay coil receives ignition voltage. The coil receives ground from the EMTC module through circuit 364 (BK/LG) if any position but OFF is selected. Voltage is supplied to the relay switch contact. When the relay coil is energized, voltage is delivered to the blower motor through circuit 371 (PK/WH). Ground for the blower motor is provided through circuit 261 (DG/BK) from the blower resistor or the blower switch (HI). The blower resistor and blower switch is grounded through circuit 1205 (BK).
Under normal operation, the blower motor is provided a ground from the blower resistor through circuit 261 (DG/BK). The resistor gets a ground from circuit 1205 (BK) in the lowest blower setting. In MED-LO and MED-HI the resistor gets a ground through circuit 754 (LG/WH) or 752 (YE/RD), depending on selected speed. In HI, the blower motor is grounded directly through the blower switch from circuit 261 (DG/BK) to circuit 1205 (BK). The blower switch receives its ground from circuit 1205 (BK).
Refrigerant Identification Testing
SPECIAL TOOL Refrigerant Identifier with Air-Radiator 198-00003 or equivalent
Scheme 1
Refrigerant Identification
Note. An A/C refrigerant analyzer must be used to identify gas samples taken directly from the refrigeration system or storage containers prior to recovering or charging the refrigerant system.
- Follow the instructions included with the refrigerant identifier to obtain the sample for testing.
- The scan tool will display one of the following: If the purity level of R-134a is 98% or greater by weight, the green PASS light emitting diode (LED) will light. The weight concentrations of R-134a, R-12, R-22, hydrocarbons and air will be displayed on the digital display. If refrigerant R-134a does not meet the 98% purity level, the red FAIL LED will light and an alarm will sound alerting the user of potential hazards. The weight concentrations of R-134a, R-12, R-22 and hydrocarbons will be displayed on the digital display. If hydrocarbon concentrations are 2% or greater by weight, the red FAIL LED will light, "Hydrocarbon High" will be displayed on the digital display, and an alarm will sound alerting the user of potential hazards. The weight concentrations of R-134a, R-12, R-22 and hydrocarbons will also be displayed on the digital display.
- The percentage of air contained in the sample will be displayed if the R-134a content is 98% or greater. The scan tool eliminates the effect of air when determining the refrigerant sample content because air is not considered a contaminant, although air can affect A/C system performance. When the scan tool has determined that a refrigerant source is pure (R-134a is 98% or greater by weight) and air concentration levels are 2% or greater by weight, the scan tool will prompt the user if an air purge is desired.
- If contaminated refrigerant is detected, repeat the refrigerant identification test to verify that the refrigerant is indeed contaminated.