B1347

Schematic:

CIRCUIT DESCRIPTION
In the process of controlling the compressor clutch, the heater and A/C programmer monitors certain inputs for an indication of a low refrigerant charge. If the system refrigerant state of charge falls below approximately 1/4 capacity, the heater and A/C programmer is capable of detecting this condition. The programmer will display VERY LOW REFRIGERANT-A/C COMPRESSOR OFF on the driver information center (DIC) in order to warn the operator.

The heater and A/C programmer determines the state of the charge by monitoring the temperature change in the low temperature sensor during the compressor engagement. This temperature drop is referenced by the heater and A/C programmer as a function of the ambient air temperature. If the refrigerant charge is too low, the refrigerant boils instantaneously after passing through the orifice tube. This action creates a large rapid change in the low temperature sensor reading. After several incidents are counted, the heater and A/C programmer sets DTC B1347.

The message VERY LOW REFRIGERANT- A/C COMPRESSOR OFF will be displayed on the DIC. If a DTC B1347 is set, the compressor clutch disengages and remains disengaged until DTC B1347 is cleared. DTC B1347 may repeat if excessive pressure exists in the A/C charging station tank. Repair the A/C charging station before properly diagnosing DTC B1347.

FAILURE CONDITIONS
The low side refrigerant temperature drops too quickly during several of the compressor cycles.

ACTION TAKEN WHEN THE DTC SETS
^ The system disables the A/C compressor until the DTC is cleared.
^ The system displays the VERY LOW REFRIGERANT-A/C COMPRESSOR OFF message on the DIC.

TEST DESCRIPTION

Steps 1-11:

1. Perform the HVAC Diagnostic System Check before continuing with the diagnosis of this DTC.
2. This test inspects for an intermittent open or short in the A/C Low Side Temp Sensor circuit.
3. This test verifies that the sensor is receiving the reference voltage.