CLUTCH - FIXED DISPLACEMENT A/C COMPRESSOR

The compressor clutch coil electrical circuit for the Denso 10SR15 and 10SR17 fixed displacement A/C compressors is controlled by the powertrain control module (PCM) or the engine control module (ECM) (depending on engine application) through the totally integrated power module (TIPM). Begin testing of a suspected compressor clutch coil problem by performing the preliminary checks.

PRELIMINARY CHECKS

1. Using a scan tool, check for diagnostic trouble codes (DTCs) in the A/C-heater control, TIPM and PCM/ECM. If no diagnostic trouble codes (DTCs) are found, go to 2. If any DTCs are found, repair as required.

2. If the A/C compressor clutch still will not engage, verify the refrigerant charge level. If the refrigerant charge level is OK, go to COIL RESISTANCE TEST and/or COIL CURRENT DRAW TEST. If the refrigerant charge level is not OK, adjust the refrigerant charge as required.

COIL RESISTANCE TEST

1. Disconnect and isolate the negative battery cable.

2. Disconnect the wire harness connector from the A/C clutch field coil connector.

3. Use an ohm meter and Back Probe Tool 6801 and measure the resistance of the clutch field coil at the field coil connector terminals.

4. Refer to the A/C CLUTCH FIELD COIL SPECIFICATIONS for the acceptable A/C clutch coil resistance. Specifications apply for a work area temperature of 21º C (70º F).

1. If the A/C clutch coil reading is below specifications, the coil is shorted and must be replaced.
2. If the A/C clutch coil reading is above specifications, the coil is open and must be replaced.

COIL CURRENT DRAW TEST

1. Verify the battery state of charge. 2. Connect an ammeter (0 to 10 ampere scale selected) in series with the clutch coil feed terminal using Back Probe Tool 6801. Connect a voltmeter (0 to 20 volt scale selected) to measure voltage across the battery and the clutch coil.

3. With the heater-A/C control in the A/C mode and the blower at low speed, start the engine and allow it to run at a normal idle speed.

4. The compressor clutch should engage immediately, and the clutch coil supply voltage should be within two volts of the battery voltage. If the coil supply voltage is OK, go to 5. If the coil supply voltage is not within two volts of battery voltage, test the clutch coil feed circuit for excessive voltage drop and repair as necessary.

5. Refer to the A/C CLUTCH FIELD COIL SPECIFICATIONS for the acceptable A/C clutch field coil current draw. Specifications apply for a work area temperature of 21º C (70º F). If voltage is more than 12.5 volts, add electrical loads by turning on electrical accessories until voltage reads below 12.5 volts.

1. If the compressor clutch coil current reading is zero, the coil is open and must be replaced.
2. If the compressor clutch coil current reading is above specifications, the coil is shorted and must be replaced.

A/C CLUTCH FIELD COIL SPECIFICATIONS

A/C SYSTEM NOISE TESTING

When investigating an A/C system related noise, you must first know the conditions under which the noise occurs. These conditions include: weather, vehicle speed, transmission in gear or neutral, engine speed, engine temperature, and any other special conditions. Noises that develop during A/C operation can often be misleading. For example: what sounds like a failed bearing, may be caused by loose bolts, nuts, mounting brackets or a loose A/C compressor.

NOTE: The A/C compressor must be replaced if any unusual noise is heard from the compressor itself.

1. Select a quiet area for testing. Duplicate the complaint conditions as much as possible. Turn the A/C system On and Off several times to clearly identify any compressor noise. Listen to the A/C compressor while it is operating at maximum and minimum displacement. Probe the A/C compressor with an engine stethoscope or a long screwdriver with the handle held to your ear to better localize the source of the noise. To duplicate high-ambient temperature conditions (high head pressure), restrict the air flow through the A/C condenser. Install a manifold gauge set or a scan tool to be certain that the discharge pressure does not exceed 2600 kPa (377 psi).

NOTE: Drive belts are speed sensitive. At different engine speeds and depending upon drive belt tension, drive belts can develop noises that are mistaken for an A/C compressor noise. Improper drive belt tension can cause a misleading noise when the compressor is operating at maximum displacement, which may not occur when the compressor is at minimum displacement.

2. Check the condition of the accessory drive belt.

NOTE: The A/C compressor must be replaced if the drive hub is broken or if the compressor shaft does not rotate smoothly.

3. Check the compressor hub and pulley and bearing assembly. Be certain that the hub and pulley are properly aligned and that the pulley bearing is mounted securely to the A/C compressor.

NOTE: The A/C compressor must be replaced if any debris or unusually discolored oil is found on the A/C compressor manifold.

4. Check the refrigerant system plumbing for incorrect routing, rubbing or interference, which can cause unusual noises. Also check the refrigerant lines and hoses for kinks or sharp bends that will restrict refrigerant flow, which can cause noises. 5. Loosen all of the compressor mounting hardware and retighten.

CAUTION: Do NOT run the engine with a vacuum pump in operation or with a vacuum present within the A/C system when equipped with the Denso 6SEU16 variable displacement compressor. Failure to follow this caution will result in serious A/C compressor damage.

6. If the noise is from opening and closing of the high pressure relief valve, recover, evacuate and recharge the refrigerant system. If the high pressure relief valve still does not seat properly, replace the A/C compressor.

7. If the noise is from liquid refrigerant slugging in the A/C suction line, replace the A/C receiver/drier.

8. If a slugging condition still exists after replacing the A/C receiver/drier, then replace the A/C compressor.