GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2002 🢒 Eldorado 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 DTC B1347

Circuit Description

The HVAC control processor monitors the A/C refrigerant charge through the A/C refrigerant low temperature sensor. The HVAC control processor detects low system refrigerant capacity by monitoring a change in the low temperature sensor during the A/C compressor clutch engagement. If the refrigerant charge is too low, the refrigerant boils immediately after passing through the orifice tube. This action creates a large, rapid change in the A/C refrigerant low temperature sensor reading. The message LOW REFRIGERANT-A/C OFF will be displayed on the DIC. If the DTC sets, the A/C compressor clutch will disengage.

Conditions for Running the DTC

The ignition is turned ON and the engine is running.

Conditions for Setting the DTC

The HVAC control processor detects a rapid change in the signal circuit of the A/C refrigerant low temperature sensor.

Action Taken When the DTC Sets
    • The system disables the A/C compressor until the DTC is cleared.
    • The system displays the LOW REFRIGERANT-A/C OFF message on the DIC.

Conditions for Clearing the DTC
    • The DTC will become history if the HVAC control processor no longer detects a condition.
    • The history DTC clears after 50 fault-free ignition cycles.
    • The DTC can be cleared with a scan tool.

Diagnostic Aids

If the condition is not present, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. Verify the ambient air temperature and the refrigerant level before continuing with the diagnostics of the DTC.

  2. Tests for the proper operation of the circuit in the high voltage range.

    3.

  3. Tests for the proper operation of the circuit in the low voltage range.

Step

Action

Yes

No

Schematic Reference: HVAC Schematics

1

Did you perform the HVAC Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - HVAC Systems - Automatic

2

Important: Verify that the ambient air temperature, which is displayed on the driver information center, is greater than 5.5°C (42°F). Verify that the A/C system is correctly charged. Refer to Refrigerant Recovery and Recharging and Refrigerant System Capacities in Heating, Ventilation and Air Conditiong. If the A/C system operates, verify the performance. Refer to Air Conditioning (A/C) System Performance Test in Heating, Ventilation and Air Conditioning.

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, observe the Raw Evaporator Temp. sensor parameter in the Heating and Air Conditioning Open/Short data list.

Does the scan tool display Open or Short?

Go to Step 3

Go to Diagnostic Aids

3

  1. Turn OFF the ignition.
  2. Disconnect the A/C refrigerant low temperature sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the Raw Evaporator Temp. sensor parameter.

Does the scan tool display Open?

Go to Step 4

Go to Step 5

4

  1. Turn OFF the ignition.
  2. Connect a 3-amp fused jumper between the signal circuit and the low reference circuit of the A/C refrigerant low temperature sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the Raw Evaporator Temp. sensor parameter.

Does the scan tool display Short?

Go to Step 8

Go to Step 6

5

Test the signal circuit of the A/C refrigerant low temperature sensor for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 9

6

Test the signal circuit of the A/C refrigerant low temperature sensor for a short to voltage, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 7

7

Test the low reference circuit of the A/C refrigerant low temperature sensor for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 9

8

Inspect for poor connections at the harness connector of the low temperature sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 10

9

Inspect for poor connections at the harness connector of the HVAC control processor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 11

10

Replace the A/C refrigerant low temperature sensor. Refer to Air Conditioning (A/C) Refrigerant Low Temperature Sensor Replacement in Heating, Ventilation and Air Conditioning.

Did you complete the replacement?

Go to Step 12

--

11

Important: Perform the recalibration procedure for the HVAC control processor.

Replace the HVAC control processor. Refer to HVAC Control Processor Replacement .

Did you complete the replacement?

Go to Step 12

--

12
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running in the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK