A047

Diagnostic Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION

In the process of controlling the compressor clutch, the Air Conditioning Programmer (ACP) monitors certain inputs for an indication of low refrigerant charge. If the system refrigerant state of charge should fall below approximately one third its capacity, the ACP is capable of detecting this condition and displaying a message to warn the operator.

ACP determines the state of charge by monitoring the temperature change in the LST sensor during the initial moments of compressor engagement. If refrigerant charge is too low, the refrigerant boils instantaneously after it passes through the orifice tube, creating a large rapid change in the LST sensor reading. If the temperature change is too great, a Very Low Refrigerant counter is incremented in the ACP. After several incidents have been counted, within a calibrated time, the ACP sets DTC A047 and the compressor clutch disengages. The compressor clutch remains disengaged until DTC A047 is cleared. Additionally, the ACP goes into ECON mode and the 'ECON' indicator is displayed on the Electronic Climate Control (ECC). The Driver Information Center (DIC) displays message "VERY LOW REFRIGERANT - A/C COMPRESSOR OFF" to warn the operator.

FAILURE CONDITION(S)

A047 - VERY LOW A/C REFRIGERANT CONDITION WARNING sets if the low side refrigerant temperature drops too quickly during several compressor cycles or the low refrigerant pressure switch opens during several compressor cycles.

ACTION TAKEN

1. DIC displays message "VERY LOW REFRIGERANT - A/C COMPRESSOR OFF" to warn operator.

2. Compressor clutch disengaged until DTC is cleared.

NOTES ON FAULT TREE

1. Check for intermittent open or short in pressure switch circuit.

2. Check for a restriction within the HVAC refrigerant system.

3. An offset in the ACP temperature sensors AD26 Actual Outside or AD28 Low Side may cause the triggering of a false DTC. After a long cold soak (preferably overnight) In a shaded cool environment, enter diagnostic without starting engine. All the listed sensor displays should be within 2°C of each other.

4. Recover and recharge system.

NOTES ON INTERMITTENT CONNECTION
If an intermittent DTC is being set, select ACP Snapshot Data for DTC and note value of ACP data parameter. Manipulate the related wiring while observing ACP data parameter. If a failure is induced, the displayed data parameter value will be outside the sensors normal operating range.