Monday, July 4, 2011

AC COMPRESSOR CLUTCH NOT ENGAGING ON 1994 Oldsmobile Cutlass Ciera

First put battery voltage to the a/c compressor(dk greenwire) to see if it works with the clutch ,the fan on this car does not come on until it reaches 215-226 degrees ,so at idle it may take awhile to come on ,if it is not overheating or showing hot ,worry about that later ,also crossing over the 2 wires at the coolant sensor should make the fan come on , See the electrical diagram for this system ....,crossing over the brown and light blue wires at the low pressure switch should kick on the compressor and fan

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SAME DIAGRAM ONE MORE TIME<
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CIRCUIT DESCRIPTION :
The A/C RElay is ECM controlled to delay A/C clutch engagement 0.3 seconds after A/C is turned "ON." This allows the IAC to adjust engine rpm before the A/C clutch engages. The ECM also causes the relay to disengage the A/C clutch during wot operation. The A/C relay is energized when the ECM provides a ground path for CKT 366.

TEST DESCRIPTION : Numbers below refer to circled numbers on the diagnostic chart.

  1. Checks A/C LOW pressure switch.
  2. Verifies that the A/C request signal is present at the ECM

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CIRCUIT DESCRIPTION :
The A/C Relay is ECM controlled to delay A/C clutch engagement 0.3 seconds after A/C is turned "ON." This allows the IAC to adjust engine speed before the A/C clutch engages. The ECM also causes the relay to disengage the A/C clutch during WOT operation. The A/C relay is energized when the ECM provides a ground path for CKT 366.

TEST DESCRIPTION : Numbers below refer to circled numbers on the diagnostic chart.

  1. Test light "ON" verifies the integrity of CKT 366, 639, and QDM "B" in the ECM.
  2. Test light "ON" verifies the integrity of CKT 639 to terminal "30" of the AC relay.
  3. Bypasses the relay to determine whether the relay or the compressor clutch or clutch wiring is faulty

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PURPOSE
The coolant temperature Sensor (CTS) is used to control:

  • Fuel delivery
  • Torque Converter Clutch (TCC)
  • Engine Spark Timing (EST)
  • Controlled Canister Purge (CCP)
  • Idle Air Control (IAC)
  • Cooling Fan

OPERATION:
The CTS is a thermistor that is located in the engine coolant flow. When the coolant temperature is low, the sensor produces a high resistance. When the coolant temperature is high, the sensor produces a low resistance.

The ECM sends a 5.0 volt signal to the CTS through a resistor in the computer and measures the voltage. The voltage will be high or low depending on coolant temperature. With the CTS varying its resistance, the ECM can sense engine coolant temperature by reading the varying voltage.

LOCATION:
Engine thermostat and coolant outlet.

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