HVAC System: Other Chevrolet Metro I

A/C COMPRESSOR CONTROL MODULE

The A/C compressor control module is mounted to evaporator case. Compressor control module controls operation of A/C compressor clutch in response to signals received from dual-pressure switch, evaporator temperature sensor and Powertrain Control Module (PCM). When A/C system is operating, the compressor control module engages the compressor clutch upon demand and when conditions are favorable. The PCM de-energizes the clutch when system pressure is high or low, evaporator temperature signal is low, or engine demand is high. An idle-up signal is sent to PCM, to prevent engine stalling when A/C system is on.

Air Selector Lever

Air selector lever has 5 positions. Each position controls where air will be discharged. (Scheme 3) With lever in ventilation position, cooled air or normal air is discharged from center and side registers of instrument panel.

With air selector lever in bi-level position and A/C switch in OFF position, heated air is discharged from floor vents and fresh unheated air is discharged from center and side registers.

In heater position, most of the heated air or dehumidified heated air is discharged from floor vents. In heater and defrost position, air is discharged to floor, defroster and side window defroster registers. In defrost position, most air is directed to windshield.

Fresh/Recirculated Air Control Lever

A sliding air intake select lever controls fresh air intake and recirculation of inside air. Sliding lever to left recirculates inside air. Sliding lever to right brings fresh air into passenger compartment. (Scheme 3)

Blower Speed Selector Switch

Blower switch regulates 4 blower motor speeds. (Scheme 3) In order for A/C system to operate, blower motor must be in one of 4 speeds.

Temperature Control Lever

Temperature control lever controls amount of airflow through and/or around heater core. Depending upon system control positions, mixture of warm and cold air regulates temperature and humidity of air inside of vehicle. (Scheme 3)

Scheme 3

CONDENSER

The condenser assembly is located in front of radiator. The assembly is made up of coils carrying refrigerant. Fins provide cooling for rapid transfer of heat. Air passing through condenser cools high pressure refrigerant vapor, condensing it into a liquid.

CONDENSER FAN & RELAY

The condenser fan provides airflow across condenser to dissipate heat generated by refrigerant system pressure. Air passing through condenser cools high pressure refrigerant vapor to a liquid. Failure of condenser fan circuit may cause excessive high side pressure.

The condenser fan runs continuously as long as the A/C compressor is engaged. The condenser fan receives voltage from A/C condenser fan relay.

DUAL-PRESSURE SWITCH

The dual-pressure switch is located next to right front inner fender, in the liquid line between the receiver-drier and evaporator. (Scheme 4). The switch stops compressor operation by turning off A/C compressor circuit when refrigerant pressure drops to less than 28 psi (2.0 kg/cm 2 ) or exceeds 455 psi (32 kg/cm 2 ).

Scheme 4

EVAPORATOR TEMPERATURE SENSOR

This sensor is a thermistor that converts temperature into an electrical resistance to determine evaporator core temperature. The sensor is used to prevent evaporator freeze-up. The A/C compressor control module processes information from this sensor to send signals to the compressor clutch for on-off cycling. The sensor turns the compressor clutch off at 32°F (0°C) and back on once temperature in evaporator core reaches 37°F (3°C).

Note. Evaporator temperature sensor may also be referred to as evaporator thermistor.

A/C COMPRESSOR CONTROL CHECK

1. Start engine and move blower switch to any position except off. Depress A/C button to turn A/C system on. The A/C compressor clutch should engage and cycle on and off. The blower motor should run and discharge cold air to the passenger compartment. The A/C condenser fan will turn on and cycle off and on. If system operates as specified, go to next step. If system does not operate as specified, go to appropriate TROUBLE SHOOTING procedure.
2. Depress the A/C button to turn A/C system off. The A/C compressor clutch should disengage and the condenser fan will stop running. If system operates as specified, system check is complete. If system does not operate as specified, go to appropriate TROUBLE SHOOTING procedure.

Blower Motor Inoperative Any Speed

See see HEATER SYSTEM article.

Blower Motor Operates Only In High Position

See see HEATER SYSTEM .

Blower Motor Does Not Operate In High Position

See see HEATER SYSTEM article.

Blower Motor Does Not Operate In Medium-High (M2) Position

See see HEATER SYSTEM article.

Blower Motor Does Not Operate In Medium-Low (M1) Position

See see HEATER SYSTEM article.

Blower Motor Does Not Operate In Low Position

See see HEATER SYSTEM article.

Blower Motor Operates In Off Position

See see HEATER SYSTEM article.

A/C CONDENSER FAN INOPERATIVE

1. Perform «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) . Go to next step.
2. Start engine. Turn blower switch to any position except off. Press A/C switch to on position. If compressor clutch engages, go to next step. If compressor clutch does not engage, go to «A/C COMPRESSOR CLUTCH DOES NOT ENGAGE»(ref-247-S15708557222000030800000) .
3. Using a test light connected to ground, backprobe condenser fan motor connector terminal No. 2 (Red/Blue wire). See «WIRING DIAGRAMS»(ref-247-S06892661392000030800000) . If test light comes on, go to next step. If test light does not come on, go to step 7) .
4. Check for open in Black wire between condenser fan motor and ground. If an open is found, go to next step. If wire is okay, go to step 6) .
5. Repair open in Black wire. Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .
6. Replace condenser fan motor. See «CONDENSER & CONDENSER FAN»(ref-247-S35178694542000030800000) under REMOVAL & INSTALLATION. Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .
7. Remove fuse/relay box. Fuse/relay box is located in engine compartment, near battery. Using a test light connected to ground, backprobe A/C 2 relay (condenser fan) connector terminal No. 3 (Blue/Black wire). If test light comes on, go to next step. If test light does not come on, go to step 9) .
8. Repair open Blue/Black wire (Red/Blue wire after splice) between A/C 2 relay and condenser fan motor. Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .
9. Using a test light connected to ground, backprobe A/C 2 relay connector terminal No. 4 (Red/White wire). If test light comes on, go to step 11) . If test light does not come on, go to next step.
10. Repair open in Red/White wire between A/C 2 relay and splice S122 (located in main harness at relay box). Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .
11. Using a test light connected to battery positive terminal, backprobe A/C 2 relay connector terminal No. 2 (Black wire). If test light comes on, go to step 13) . If test light does not come on, go to next step.
12. Repair open in Black wire between ground connection and A/C 2 relay. Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .
13. Check for open in Black/Red wire between A/C 2 relay connector terminal No. 1 and splice S123. Splice is located in main harness approximately 2" (5 cm) from brake fluid level switch connector breakout. If open is found, go to next step. If wire is okay, go to step 15) .
14. Repair open in Black/Red wire. Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .
15. Replace A/C 2 relay. Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .

A/C CONDENSER FAN RUNS AT ALL TIMES

1. Perform «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) . Go to next step.
2. Start engine. If A/C compressor clutch is engaged, go to «A/C COMPRESSOR CLUTCH ALWAYS ENGAGED»(ref-247-S37131158852000030800000) . If compressor clutch is not engaged, go to next step.
3. Remove A/C 2 relay (condenser fan) from fuse/relay box. Fuse/relay box is located in engine compartment, near battery. If fan stops, go to next step. If fan does not stop, go to step 5) .
4. Replace A/C 2 relay. Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .
5. Repair short to voltage in Blue/Black wire (Red/Blue wire after splice) wire between A/C 2 relay and condenser fan motor. See «WIRING DIAGRAMS»(ref-247-S06892661392000030800000) . Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .

A/C COMPRESSOR CLUTCH DOES NOT ENGAGE

1. Perform «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) . Go to next step.
2. Ensure A/C system is fully charged and no leaks are present. Start engine. Press A/C switch to on position. Move blower speed selector switch to any position other than OFF. Using a test light connected to ground, backprobe compressor clutch connector terminal (Black wire). See «WIRING DIAGRAMS»(ref-247-S06892661392000030800000) . If test light does not come on, go to step 4) . If test light comes on, go to next step.
3. Replace A/C compressor clutch. Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .
4. Remove fuse/relay box from front wheelwell. Using a test light connected to ground, backprobe A/C 1 relay (compressor clutch) connector terminal No. 3 (Black/Red wire). If test light does not come on, go to step 6) . If test light comes on, go to next step.
5. Repair open Black/Red wire between compressor clutch and A/C 1 relay. Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .
6. Using a test light connected to ground, backprobe A/C 1 relay connector terminal No. 4 (Red/White wire). If test light comes on, go to step 8) . If test light does not come on, go to next step.
7. Repair open Red/White wire between A/C 1 relay and A/C fuse. Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .
8. Using a test light connected to ground, backprobe A/C 1 relay connector terminal No. 1 (Light Green wire). If test light comes on, go to step 10) . If test light does not come on, go to next step.
9. Repair open Light Green wire. Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .
10. Disconnect A/C compressor control module connector. A/C compressor control module is mounted to evaporator case. Connect a fused jumper wire between compressor control module harness connector terminal No. 7 (Pink wire) and ground. If compressor clutch engages, go to next step. If compressor clutch does not engage, go to step 12) .
11. Connect a test light between A/C compressor control module connector terminal No. 8 (Black/White wire) and ground. If test light comes on, go to step 16) . If test light does not come on, go to step 15) .
12. Using a fused jumper wire, backprobe A/C 1 relay connector between terminal No. 2 (Pink wire) and ground. If compressor clutch does not engage, go to next step. If clutch engages, go to step 14) .
13. Replace A/C 1 relay. Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .
14. Repair open in Pink wire. Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .
15. Repair open Black/White wire between A/C compressor control module and splice S202. Splice is located in main harness, approximately 3" (8 cm) from junction block connector C6 breakout. Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .
16. Connect test light between A/C compressor control module connector terminal No. 3 (Black/Blue wire) and battery voltage. If test light comes on, go to step 18) . If test light does not come on, go to next step.
17. Repair open in Black wire between A/C compressor control module and ground connection. Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .
18. Connect test light between A/C compressor control module connector terminal No. 9 (Black wire) and battery voltage. If test light comes on, go to step 21) . If test light does not come on, go to next step.
19. Check ground G201, behind left kick panel, for bad ground connection. Repair as necessary. Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) . If ground is okay, go to next step.
20. Repair open in Black wire between A/C compressor control module and ground. Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .
21. Connect a test light between ground and A/C compressor control module connector terminal No. 11 (Blue/White wire). If test light does not come on, go to next step. If test light comes on, go to step 23) .
22. Using a test light connected to ground, backprobe A/C switch connector terminal No. 2 (Blue/White wire). If test light does not come on, go to step 24) . If test light comes on, go to step 25) .
23. Connect a test light between A/C compressor control module connector terminal No. 12 (Orange/Black wire) and battery voltage. If test light comes on, go to step 28) . If test light does not come on, go to step 29) .
24. Using a test light connected to ground, backprobe A/C switch connector terminal No. 1 (Pink/Black wire). If test light comes on, go to step 26) . If test light does not come on, go to step 27) .
25. Repair open Blue/White wire between A/C switch and A/C compressor control module. Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .
26. Replace A/C switch. See see «HEATER SYSTEM»(ref-244) article. Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .
27. Repair open Pink/Black wire between A/C switch and wire splice S233. Splice is located in instrument panel harness, approximately 3" (8 cm) from A/C-heater control panel harness breakout. Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .
28. Disconnect evaporator temperature sensor connector at evaporator case. Using a DVOM, check resistance between temperature sensor connector terminals. Resistance check must be made at room temperature. If resistance is 2000 ohms or less, go to step 34) . If resistance is more than 2000 ohms, go to step 33) .
29. Using a test light connected to battery positive voltage, backprobe dual-pressure switch connector terminal No. 1 (Black wire). If test light comes on, go to next step. If test light does not come on, go to step 32) .
30. Check for open in Orange/Black wire between A/C compressor control module and dual-pressure switch. If open is found, go to step 40) . If wire is okay, go to next step.
31. Replace dual-pressure switch. See «DUAL-PRESSURE SWITCH»(ref-247-S25314332982000030800000) under REMOVAL & INSTALLATION. Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .
32. Repair open Black wire between dual-pressure switch and ground G103. Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .
33. Replace evaporator temperature sensor. See «EVAPORATOR CORE, EXPANSION VALVE & EVAPORATOR TEMPERATURE SENSOR»(ref-247-S38760804532000030800000) under REMOVAL & INSTALLATION. Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .
34. Reconnect evaporator temperature sensor. Using a DVOM, check resistance between A/C compressor control module connector terminals No. 4 (White/Blue wire) and No. 10 (Yellow/Green wire). If resistance is more than 2000 ohms, go to next step. If resistance is 2000 ohms or less, go to step 36) .
35. Repair open in White/Blue wire or Yellow/Green wire between A/C compressor control module and evaporator temperature sensor. Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .
36. Disconnect Powertrain Control Module (PCM) 22-pin Gray connector C-3. PCM is located behind left side of instrument panel, near steering column. Using a DVOM, check resistance between A/C compressor control module connector terminal No. 5 (Light Green/Red wire) and ground. If resistance is infinite, go to next step. If resistance is not infinite, go to step 38) .
37. Repair short to ground in Light Green/Red wire between A/C compressor control module and PCM. Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .
38. Reconnect PCM connector C-3. Remove Light Green/Red wire from A/C compressor control module connector terminal No. 5. Reconnect A/C compressor control module. Using a test light connected to ground, backprobe A/C compressor clutch connector terminal. If test light comes on, check for PCM diagnostic trouble codes and repair as necessary. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If test light does not come on, go to next step.
39. Replace A/C compressor control module. See «A/C COMPRESSOR CONTROL MODULE»(ref-247-S09612714482000030800000) under REMOVAL & INSTALLATION. Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .
40. Repair open in Orange/Black wire. Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .

A/C COMPRESSOR CLUTCH ALWAYS ENGAGED

1. Perform «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) . Go to next step.
2. Start engine. Disconnect A/C switch connector. If compressor is still engaged, go to step 4) . If compressor is not engaged, go to next step.
3. Replace A/C switch. See see «HEATER SYSTEM»(ref-244) article. Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .
4. Disconnect A/C compressor control module connector. A/C compressor control module is mounted to evaporator case. Connect a test light between A/C switch connector terminal No. 2 (Blue/White wire) and ground. See «WIRING DIAGRAMS»(ref-247-S06892661392000030800000) . If test light does not come on, go to step 6) . If test light comes on, go to next step.
5. Repair short to voltage in Blue/White wire between A/C switch and A/C compressor control module. Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .
6. Remove fuse/relay box from wheelwell. Disconnect A/C 1 and A/C 2 relays (compressor clutch) connector and condenser fan relay connectors. If compressor clutch is not engaged, go to step 8) . If compressor clutch is engaged, go to next step.
7. Repair short to voltage in Black/Red wire between A/C 1 relay, A/C 2 relay (condenser fan) and splice S123. Splice is located in main harness, approximately 2" (5 cm) from brake fluid level switch connector breakout. Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .
8. Reconnect condenser fan relay connector. If compressor clutch is not engaged, go to step 10) . If compressor clutch is engaged, go to next step.
9. Replace A/C 2 relay (condenser fan). Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .
10. Using a DVOM, check resistance between A/C 1 relay connector terminal No. 2 (Pink wire) and ground. If resistance is infinite, go to step 12) . If resistance is not infinite, go to next step.
11. Repair short to ground in Pink wire between compressor clutch relay and A/C compressor control module. Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .
12. Reconnect A/C 1 (compressor clutch) relay connector. If compressor clutch is not engaged, go to step 14) . If compressor clutch is engaged, go to next step.
13. Replace A/C 1 (compressor clutch) relay. Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .
14. Replace A/C compressor control module. See «A/C COMPRESSOR CONTROL MODULE»(ref-247-S09612714482000030800000) under REMOVAL & INSTALLATION. Go to «A/C COMPRESSOR CONTROL CHECK»(ref-247-S00063047862000030800000) .

A/C SYSTEM PERFORMANCE

1. Turn ignition switch to locked position. Apply parking brake. Open hood. Connect A/C manifold gauge set to vehicle. Start engine, warm up to normal operating temperature, and allow it to run at idle.
2. Open all doors and windows. Set air mode to ventilation, recirculated air mode, temperature control at full cold, A/C on and blower motor speed to high. Place thermometer in instrument panel center outlet.
3. Observe manifold gauge set and thermometer, then record pressures and temperature once they stabilize. Compare pressures and outlet air temperature with «PRESSURE SPECIFICATIONS»(ref-247-S41492883592000030800000) and «OUTLET TEMPERATURE SPECIFICATIONS»(ref-247-S12827840602000030800000) tables. Service A/C refrigerant system as necessary.

PRESSURE SPECIFICATIONS

OUTLET TEMPERATURE SPECIFICATIONS

A/C 1 RELAY (COMPRESSOR CLUTCH) & A/C 2 RELAY (CONDENSER FAN)

Remove relay from fuse/relay box. Fuse/relay box is located in engine compartment, near battery. Connect battery voltage between relay terminals No. 1 and 3. (Scheme 5) Using a DVOM, check continuity between relay terminals No. 2 and 4. Continuity should exist. If continuity does not exist, replace relay.

Scheme 5

EXPANSION VALVE

1. Remove expansion valve. See «EVAPORATOR CORE, EXPANSION VALVE & EVAPORATOR TEMPERATURE SENSOR»(ref-247-S38760804532000030800000) under REMOVAL & INSTALLATION. Connect A/C manifold gauge set to expansion valve. Connect gauge set charging hose to R-134a refrigerant bottle. (Scheme 6) Soak expansion valve's sensing bulb in water.
2. Close both high and low pressure valves. Open valve to refrigerant bottle. Open high pressure valve to approximately 70 psi (5.0 kg/cm 2 ). Read and record low pressure gauge reading. Measure temperature of water.
3. Pressure/temperature relationship should be within specification. See «EXPANSION VALVE SPECIFICATIONS»(ref-247-S11715642172000030800000) table. If pressure/temperature relationship is not within specification, replace expansion valve.

EXPANSION VALVE SPECIFICATIONS

Scheme 6