Engine Controls - System/component Tests Eagle Talon I

INTRODUCTION

Before testing separate components or systems, perform procedures in BASIC TESTING article in this Section. Since many computer-controlled and monitored components set a trouble code if they malfunction, also perform procedures in G - TESTS W/ CODES article in this section.

Note. Testing individual components does not isolate shorts or opens. Perform all voltage tests with a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure. Use ohmmeter to isolate wiring harness shorts or opens.

Turbocharger Pressure Check

1. Disconnect turbocharger pressure control hose at wastegate solenoid valve (attached to air cleaner) and plug nipple. Attach pressure gauge to hose. (Scheme 9)
2. Drive vehicle and accelerate engine, in 2nd gear, to greater than 3500 RPM. Measure turbocharger pressure when pressure gauge stabilizes. On M/T models, pressure gauge should read 6-12 psi (.4-.8 kg/cm 2 ). On A/T models, pressure gauge should read 6-10 psi (.4-.7 kg/cm 2 ).
3. If pressure gauge reading is more than specified, check wastegate actuator. See WASTEGATE ACTUATOR TEST below. Replace wastegate actuator as required. If pressure gauge reading is less than specified, check for malfunctioning wastegate valve, turbocharger pressure leaks and faulty turbocharger.

Scheme 9

Wastegate Actuator Test

Wastegate actuator is mounted on turbocharger. (Scheme 9) On M/T models, apply a pressure of 11 psi (.8 kg/cm 2 ) to wastegate actuator. On A/T models, apply a pressure of 10 psi (.7 kg/cm 2 ) to wastegate actuator. On all models, check that wastegate actuator rod moves. Replace wastegate actuator if rod does not move or actuator does not hold pressure.

Wastegate Solenoid Valve

1. Wastegate solenoid valve is located on air cleaner assembly. Disconnect wastegate solenoid valve electrical connector and vacuum hose.
2. Connect a hand-held vacuum pump to wastegate solenoid valve fitting where vacuum hose was connected. Apply vacuum. Vacuum should hold. If vacuum does not hold, replace wastegate solenoid valve. If vacuum holds, go to next step.
3. With wastegate solenoid valve electrical connector disconnected, apply battery voltage to wastegate solenoid valve terminals. Apply vacuum with hand-held vacuum pump. Vacuum should not hold. If vacuum holds, replace wastegate solenoid valve. If wastegate solenoid valve does not hold vacuum, go to next step.
4. Using an ohmmeter, check wastegate solenoid valve resistance. Connect ohmmeter leads between wastegate solenoid valve terminals. Ohmmeter should read 36-44 ohms at 68°F (20°C). If resistance is not within specification, replace wastegate solenoid valve.

Air By-Pass Valve

1. Air by-pass valve is located on intercooler inlet water hose. Remove air by-pass valve.
2. Check if air by-pass valve is closed. If air by-pass valve is open, replace valve. If air by-pass valve is closed, go to next step.
3. Connect a hand-held vacuum pump to air by-pass valve vacuum fitting. Apply 16 in. Hg vacuum. Valve should open when vacuum is applied. If valve does not open, replace air by-pass valve.

Purge Control Valve

See EMISSION SYSTEMS & SUB-SYSTEMS .

Harness Check

1. If during SELF-DIAGNOSTICS testing, Electronic Control Unit (ECU) is found to be faulty, perform the following steps to confirm diagnosis.
2. Most components are incorrectly diagnosed due to faulty electrical connectors or poor connections between component and vehicle.
3. Sometimes, simply disconnecting and connecting an electrical component will provide a good electrical connection. Before replacing ECU, check all components in suspected circuit. If components are okay, carefully disconnect ECU from vehicle harness.
4. Inspect ECU harness connector and ECU contact pins for corrosion. Clean harness connector and ECU contact pins with contact cleaner.
5. Inspect ECU harness connector for bent pins, missing pins and broken wires. Repair or replace as necessary.
6. Connect ECU harness connector to ECU and retest system with Diagnostic Readout Box (DRB-II) or similar scan tester. See appropriate G - TESTS W/ CODES article in this Section. If vehicle does not pass test and fails with the same message, replace ECU.

Airflow Sensor

1. Airflow sensor is located inside air cleaner assembly. Disconnect airflow sensor electrical connector. Using an ohmmeter, measure resistance between airflow sensor connector terminals No. 4 and 6 (non-turbo models), or terminals No. 6 and 8 (turbo models). (Scheme 10)
2. Resistance should be approximately 6000 ohms at 32°F (0°C), 2700 ohms at 68°F (20°C) and 400 ohms at 176°F (80°C). Note that as temperature increases, resistance decreases.
3. If airflow sensor resistance is not as specified or if resistance remains unchanged, replace airflow sensor.

Scheme 10

Coolant Temperature Sensor

1. Coolant temperature sensor is located on intake manifold. Remove coolant temperature sensor. Place sensing portion of coolant temperature sensor in water.
2. Gradually heat water and read resistance values across terminals. See «COOLANT TEMPERATURE SENSOR RESISTANCE»(/eagle/talon/i-1989-1994/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. If coolant temperature sensor resistance is not within specification, replace sensor.

COOLANT TEMPERATURE SENSOR RESISTANCE

Crank Angle Sensor

On all 2.0L engines, crank angle sensor is located on rear side of cylinder head, coupled to intake camshaft. On 1.8L engines, crank angle sensor is located inside distributor. For testing procedure, see appropriate G - TESTS W/ CODES article in this section.

Detonation Sensor (2.0L Turbo)

Detonation sensor is located on left side of cylinder block (firewall side). For testing procedure, see appropriate G - TESTS W/ CODES article in this section.

EGR Temperature Sensor (California Models)

See EMISSION SYSTEMS & SUB-SYSTEMS .

Idle Position Switch (1.8L)

1. Idle position switch is integral with idle speed control servo, located on throttle body. Disconnect motor position sensor connector. Using an ohmmeter, check continuity between motor position sensor connector terminal No. 4 and body ground. (Scheme 11)
2. With accelerator pedal depressed, continuity should not exist. With accelerator pedal released, continuity should exist. Replace idle speed control servo assembly if switch does not test as specified.

Scheme 11

Idle Position Switch (2.0L & 2.0L Turbo)

1. Idle position switch is located on throttle body. Disconnect idle position switch connector. Using an ohmmeter, check continuity between switch terminal and ground.
2. With accelerator pedal depressed, no continuity should exist. With accelerator pedal released, continuity should exist. Replace idle position switch if it does not test as specified.

Motor Position Sensor & Idle Speed Control Servo (1.8L)

1. Motor position sensor is integral with idle speed control servo, located on throttle body. Disconnect motor position sensor connector. Using an ohmmeter, measure resistance between motor position sensor terminals No. 2 and 3. (Scheme 11) Ohmmeter should read 4000-6000 ohms.
2. If resistance is not within specification, replace idle speed control servo. If resistance is within specification, go to next step. CAUTION: When activating idle speed control plunger, DO NOT apply more than 6 volts. Higher voltage may cause damage to servo gears.
3. Disconnect idle speed control servo connector. Connect a 6-volt power source between idle speed control servo terminals No. 1 and 2 to activate idle speed control servo plunger. (Scheme 11)
4. Using an ohmmeter, measure resistance between motor position sensor terminals No. 3 and 5 when idle speed control servo plunger is activated. Ohmmeter should read 4000-6000 ohms.
5. Replace idle speed control servo if resistance is not within specification, or if idle speed control servo plunger does not extend and retract smoothly.

Oxygen Sensor (1.8L)

1. Oxygen sensor is located at outlet of exhaust manifold. Warm engine until coolant temperature reaches 185-205°F (85-95°C).
2. Disconnect oxygen sensor connector and connect a voltmeter to connector. With engine speed greater than 1300 RPM, measure oxygen sensor output voltage. Output voltage should be .6-1.0 volt. If output voltage is not within specification, replace oxygen sensor.

Oxygen Sensor (2.0L & 2.0L Turbo)

1. Oxygen sensor is located at outlet of exhaust manifold or turbocharger. Warm engine until coolant temperature reaches 185-205°F (85-95°C).
2. Disconnect oxygen sensor connector. Using an ohmmeter, measure resistance between oxygen sensor terminals No. 3 and 4. (Scheme 12)
3. Resistance of a cold oxygen sensor should be approximately 12 ohms with an oxygen sensor temperature of 68°F (20°C). A hot oxygen sensor should have resistance of 30 ohms or more with an oxygen sensor temperature of 752°F (400°C).
4. If oxygen sensor resistance is not as specified, replace oxygen sensor. If resistance is okay, go to next step. CAUTION: Damage to oxygen sensor may result if battery voltage is applied to wrong oxygen sensor terminals.
5. Apply battery voltage across oxygen sensor terminals No. 3 and 4. (Scheme 12) Connect a digital voltmeter to oxygen sensor terminals No. 1 and 2.
6. With engine speed greater than 1300 RPM, measure oxygen sensor output voltage. Output voltage should be.6-1.0 volt. If output voltage is not within specification, replace oxygen sensor.

Scheme 12

Power Steering Pressure Switch

1. Power steering pressure switch is located on side of power steering pump. Disconnect power steering pressure hose from power steering pump. Connect, in series, a pressure gauge shutoff valve assembly capable of handling 250 psi (17.5 kg/cm 2 ), 2 tee-in pressure hoses and appropriate adapters. (Scheme 13)
2. Bleed air from system by grounding coil wire and cranking engine while turning steering wheel all the way from left to right 6 times. Start engine and turn steering wheel back and forth to raise fluid temperature to approximately 122-140°F (50-60°C).
3. With engine idling, disconnect electrical connector from oil pressure switch, and connect an ohmmeter to pressure switch terminal and engine ground.
4. Gradually close shutoff valve to pressure gauge to increase hydraulic pressure. Ensure pressure switch is closed (ohmmeter shows continuity) at a pressure of 213-284 psi (14.9-19.9 kg/cm 2 ).
5. Gradually open shutoff valve and ensure switch is open (ohmmeter shows no continuity) at 100-171 psi (7-12 kg/cm 2 ). Remove testing equipment. Bleed air from system by grounding coil wire and cranking engine while turning steering wheel all the way from left to right 6 times. Replace power steering switch if it does not test as specified.

Scheme 13

Throttle Position Sensor (TPS)

1. TPS is located on throttle body. Disconnect TPS connector. Measure resistance between TPS terminals No. 4 (sensor ground) and No. 1 (sensor power). (Scheme 14)
2. Resistance should be approximately 3500-6500 ohms. If resistance is not within specification, replace TPS. If resistance is within specification, go to next step.
3. Connect an ohmmeter between terminals No. 4 (sensor ground) and No. 2 (sensor output). (Scheme 14) Operate throttle valve slowly from idle position to fully open position. Resistance should change smoothly in proportion to throttle valve opening angle. Replace TPS if it does not test as described.

Scheme 14

Vehicle Speed Sensor

1. Vehicle speed sensor is located in speedometer. (Scheme 15) Connect ohmmeter across reed switch terminals and rotate speedometer cable. (Scheme 16)
2. Ohmmeter reading should fluctuate between continuity and no continuity when speedometer is rotated. Replace vehicle speed sensor if it does not test as described.

Scheme 15

Scheme 16

RELAYS

Control Relay (1.8L)

1. Control relay is located on right side of center console. Disconnect control relay connector. Using an ohmmeter, measure resistance between control relay terminals No. 3 and 5, and terminals No. 2 and 5. (Scheme 17) Resistance should be about 95 ohms. If resistance is about 95 ohms, go to next step. If resistance is not as specified, replace relay.
2. Measure resistance between control relay terminals No. 6 and 7. Resistance should be about 35 ohms. If resistance is about 35 ohms, go to next step. If resistance is not as specified, replace relay.
3. Check for continuity between terminals No. 6 and 8 in both directions. Continuity should exist in one direction only (circuit is equipped with diode). If continuity is okay, go to next step. If continuity is not okay, replace relay.
4. Using a 12-volt power source, connect positive lead terminal No. 7 and negative lead to terminal No. 6. Using an ohmmeter, check for continuity between terminals No. 1 and 4. Continuity should exist. Disconnect negative lead from terminal No. 6, continuity should not exist. If continuity is as specified, go to next step. If continuity is not as specified, replace relay.
5. Connect positive lead to terminal No. 8 and negative lead to terminal No. 6. Using an ohmmeter, check for continuity between terminals No. 2 and 4. If continuity exists, go to next step. If continuity does not exist, replace relay.
6. Disconnect negative lead from terminal No. 6. Check for continuity between terminals No. 2 and 4. Continuity should not exist. If continuity exists, replace relay.

Scheme 17

Control Relay (2.0L & 2.0L Turbo)

1. Control relay is located on right side of center console. Disconnect control relay connector.
2. Using a 12-volt power source, connect positive lead to control relay terminal No. 10 and negative lead to terminal No. 8. (Scheme 18) Using a voltmeter, check for voltage at terminals No. 4 and No. 5. Battery voltage should exist. Disconnect negative lead from terminal No. 8. Voltage should no longer exist at terminals No. 4 and No. 5.
3. Connect negative lead to terminal No. 6. Ensure continuity is NOT present at terminals No. 2 and 3. Connect positive lead to terminal No. 9 and negative lead to terminal No. 6. Continuity should exist between terminals No. 2 and No. 3.
4. Connect positive lead to terminal No. 3. If voltage exists at terminal No. 2, repair short to ground. Connect positive lead to terminal No. 3 and negative lead to terminal No. 7. If battery voltage does not exist at terminal No. 2, replace control relay.

Scheme 18

EGR Control Solenoid Valve (California Models)

See EMISSION SYSTEMS & SUB-SYSTEMS .

Fuel Pressure Control Solenoid Valve (2.0L Turbo)

1. Mark fuel pressure control valve vacuum hoses for installation reference. Disconnect fuel pressure control valve Blue-striped and Black vacuum hoses. Disconnect fuel pressure control valve electrical connector.
2. Using a 12-volt power source, connect positive and negative leads to fuel pressure control solenoid valve terminals. Using a hand-held vacuum pump, apply vacuum to fitting where Black vacuum hose was connected. Vacuum should hold.
3. Disconnect battery voltage. Place a finger over other vacuum fitting and apply vacuum again. Vacuum should hold. Remove finger. Vacuum should no longer hold.
4. Using an ohmmeter, check resistance between fuel pressure control solenoid valve terminals. Resistance should be approximately 36-46 ohms at 68°F (20°C). If fuel pressure control solenoid valve does not test as specified, replace solenoid valve.

Purge Control Solenoid Valve

See EMISSION SYSTEMS & SUB-SYSTEMS .

FUEL DELIVERY

Note. For fuel system pressure testing, see appropriate BASIC TESTING article in this section.

Fuel Injector Operating Check

Using a stethoscope, check injector operating sound during engine cranking and idling. Ensure operating sound increases as engine RPM is increased.

Fuel Injector Resistance Check

1. Disconnect fuel injector connector. Using an ohmmeter, measure resistance between fuel injector terminals.
2. On 1.8L and 2.0L non-turbo, resistance should be 13-16 ohms at 68°F (20°C).
3. On 2.0L turbo, resistance should be 2-3 ohms at 68°F (20°C). On all models, if resistance is not to specification, replace fuel injector.

IDLE CONTROL SYSTEM

Idle Speed Control Servo (1.8L)

1. Idle speed control servo is located on throttle body. Disconnect idle speed control servo connector. Check continuity of idle speed control servo coil.
2. Using an ohmmeter, check resistance between idle speed control servo connector terminals No. 1 and 2. (Scheme 11) Ohmmeter should read 5-35 ohms at 68°F (20°C). Connect a 6-volt power source across idle speed control servo connector terminals No. 1 and 2. Idle speed control servo should operate. Replace idle speed control servo if it does not test as described.

IGNITION SYSTEM

Note. For basic ignition checks, see appropriate BASIC TESTING article in this section.

Detonation sensor is located on left side of cylinder block (firewall side). For testing procedure, see appropriate G - TESTS W/ CODES article in this section.

Ignition Coil (1.8L)

Using an ohmmeter, measure resistance of primary and secondary coil. Primary coil resistance should be .9-1.2 ohms at 68°F (20°C). Secondary resistance should be 1900-27,000 ohms at 68°F (20°C).

Ignition Coil (2.0L & 2.0L Turbo)

1. Disconnect ignition coil connector. Using an ohmmeter, measure primary coil resistance between ignition coil terminals No. 3 and 2. (Scheme 19), TEST 1. Also, measure resistance between ignition coil connector terminals No. 3 and 1. Primary resistance should be.77-.95 ohms at 68°F (20°C).
2. With ignition coil connector still disconnected, measure secondary coil resistance. Measure resistance between high-voltage terminals for cylinders No. 1 and 4, and between high-voltage terminals for cylinders No. 2 and 3. (Scheme 19), TEST 2.
3. Secondary resistance should be 10,300-13,900 ohms. Replace ignition coil if it does not test as described.

Scheme 19

Note. To test power transistors, use an analog ohmmeter.

Power Transistor (1.8L)

1. Connect ohmmeter leads between power transistor terminals No. 5 and 8. (Scheme 20) Using a 1.5-volt dry cell battery, connect positive battery lead to power transistor terminal No. 6 and negative lead to terminal No. 5.
2. Check for continuity with dry cell battery connected and disconnected. Continuity should exist with battery connected. No continuity should exist with battery disconnected. If power transistor does not test as specified, replace power transistor.

Scheme 20

Power Transistor (2.0L & 2.0L Turbo)

1. To check power transistor for cylinders No. 1 and 4, connect ohmmeter leads between power transistor terminals No. 3 and 7. (Scheme 21), TEST 1. Using a 1.5-volt dry cell battery, connect positive battery lead to power transistor terminal No. 6 and negative lead to terminal No. 3.
2. Check for continuity with dry cell battery connected and disconnected. Continuity should exist with battery connected. No continuity should exist with battery disconnected.
3. To check power transistor for cylinders No. 2 and 3, connect ohmmeter between power transistor terminals No. 1 and 3. (Scheme 21), TEST 2. Using 1.5-volt dry cell battery, connect positive battery lead to power transistor terminal No. 2 and negative lead to terminal No. 3.
4. Check for continuity with dry cell battery connected and disconnected. Continuity should exist with battery connected. No continuity should exist with battery disconnected. If transistor(s) do not test as described, replace power transistor(s).

Scheme 21

EGR System Inspection (Federal & Canadian)

1. Disconnect Green-striped vacuum hose from EGR valve at throttle body. Plug fitting at throttle body where vacuum hose was connected. Connect a hand-held vacuum pump to Green-striped vacuum hose.
2. With engine cold and coolant temperature less than 104°F (40°C), start engine and let idle. Using hand-held vacuum pump, try applying vacuum. Vacuum should not hold.
3. Run engine until coolant temperature is greater than 176°F (80°C). With engine idling, apply 2 in. Hg vacuum. Ensure vacuum holds.
4. Apply 8.5 in. Hg vacuum. If idle becomes unstable, engine stalls and vacuum holds, system is okay. If EGR system does not function as described, perform individual component testing.

EGR System Inspection (California)

1. Connect a vacuum "T" into Green-striped vacuum hose from EGR valve and connect a hand-held vacuum pump to vacuum "T".
2. Start engine and let idle. With engine cold and coolant temperature less than 68°F (20°C), snap throttle open to race engine. If no change in vacuum reading is observed, system is okay.
3. Run engine until coolant temperature is greater than 158°F (70°C). Snap throttle open to race engine. If vacuum increases to 4 in. Hg vacuum or more, system is okay.
4. Disconnect vacuum pump from vacuum "T" and connect it directly to EGR valve. Apply 8.5 in. Hg vacuum, ensure engine stops, or idle becomes unstable. If engine stops or idle becomes unstable, system is okay. If EGR system does not function as described, perform individual component testing.

EGR Valve (Except Federal & Canadian 1.8L)

1. Remove EGR valve and check valve for sticking and carbon deposits. Clean EGR valve to ensure tight valve seat contact. Connect a hand-held vacuum pump to EGR valve.
2. Apply 19 in. Hg vacuum and ensure vacuum holds. Ensure air blows through EGR ports. Release vacuum and apply 1.8 in. Hg vacuum or less. Ensure air does not blow through EGR ports. If EGR valve does not test as described, replace EGR valve.

EGR Temperature Sensor (California)

1. Remove EGR temperature sensor located below EGR valve. Place sensing portion of exhaust gas temperature sensor in water.
2. Gradually heat water and read resistance values across terminals. See «TESTING EGR TEMPERATURE SENSOR»(/eagle/talon/i-1989-1994/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. Replace exhaust gas temperature sensor if resistance is not within specification.

TESTING EGR TEMPERATURE SENSOR

Thermovalve (Federal & Canadian)

1. Mark vacuum hoses for installation reference. Disconnect vacuum hoses from thermovalve. Connect a hand-held vacuum pump to thermovalve fitting. Apply vacuum.
2. With engine coolant temperature less than 122°F (50°C), vacuum should not hold. With engine coolant temperature greater than 176°F (80°C), vacuum should hold. Replace thermovalve if it does not function as described.

EGR Control Solenoid Valve (California)

1. Mark vacuum hoses for installation reference. Disconnect Yellow and Green-striped vacuum hose from EGR control solenoid valve.
2. Disconnect EGR control solenoid valve electrical connector. Connect a hand-held vacuum pump where Green-striped vacuum hose was connected. Apply battery voltage to EGR solenoid valve terminals.
3. Apply vacuum with hand-held vacuum pump. When battery voltage is applied, vacuum should hold. When battery voltage is disconnected, vacuum should not hold.
4. Disconnect battery voltage. Using an ohmmeter, check EGR control solenoid valve resistance. Resistance should be 36-44 ohms at 68°F (20°C). Replace EGR control solenoid valve if it does not test as described.

Purge Control System Inspection

1. Disconnect Red-striped vacuum hose from purge control solenoid valve at throttle body. Plug throttle body fitting. Connect a hand-held vacuum pump to Red-striped vacuum hose. Plug fitting at throttle body where Red-striped vacuum hose was connected.
2. With engine cold and coolant temperature less than 140°F (60°C), start engine and let idle. Apply 15 in. Hg vacuum. Ensure vacuum holds. Increase engine speed to 3000 RPM. With vacuum maintained at 15 in. Hg, vacuum should still hold. Warm engine until coolant temperature is greater than 158°F (70°C).
3. Within 3 minutes after starting engine, increase engine speed to 3000 RPM. Using hand-held vacuum pump, try applying vacuum. Ensure vacuum does not hold. Reduce engine speed to idle. With engine idling, apply 15 in. Hg vacuum. Ensure vacuum holds. NOTE: When performing next step, if altitude is greater than 7200 feet or intake air temperature is greater than 122°F (50°C), vacuum will leak continuously.
4. After 3 minutes have elapsed from starting engine, increase engine speed to 3000 RPM. Apply 15 in. Hg vacuum. Vacuum should hold momentarily then leak.
5. If purge control system does not function as described, perform individual component testing.

1. Mark purge control solenoid valve vacuum hoses for installation reference. Disconnect Black and Red-striped vacuum hose from purge control solenoid valve.
2. Disconnect purge control solenoid valve electrical connector. Connect a hand-held vacuum pump to fitting where Red-striped vacuum hose was connected. Apply vacuum. Connect battery voltage to purge control valve terminals.
3. On non-turbo models, when battery voltage is applied, vacuum should not hold; when battery voltage is disconnected, vacuum should hold. On turbo models, when battery voltage is applied vacuum should hold; when battery voltage is disconnected, vacuum should not hold.
4. On all models, measure resistance between purge control solenoid valve terminals. Resistance should be 36-44 ohms at 68°F (20°C). Replace purge control solenoid valve if it does not function as described.

Purge Control Valve (2.0L Turbo)

1. Remove purge control valve. Lightly blow air into purge control valve fitting "D". (Scheme 22) Ensure air does not blow through to fitting "C".
2. Using a hand-held vacuum pump, apply 8 in. Hg vacuum to fitting "A". Lightly blow air into purge control valve fitting "D". Ensure air blows through to fitting "C".
3. Apply 16 in. Hg vacuum, in turn, to fitting "A" and fitting "B". (Scheme 22) Ensure vacuum holds both times. Replace purge control valve if it does not test as described.

Scheme 22

PCV Valve

Remove PCV valve from valve cover. Start engine and let idle. Put finger over opening of PCV valve. Ensure a vacuum is felt with finger. If vacuum is not felt, clean or replace PCV valve as necessary.

MISCELLANEOUS CONTROLS

Note. Although some of the controlled devices listed here are not technically engine performance components, they can affect driveability if they malfunction.

A/C Control Unit

1. A/C switch is located above A/C-heater unit. (Scheme 23) Disconnect A/C control unit electrical connector. Turn ignition switch and A/C switch to the ON position. Set temperature control lever to MAX COOL and blower switch to HI position. NOTE: Refer to Fig. (Scheme 24) during the following testing procedure.
2. Using an ohmmeter, measure resistance between terminals No. 1 and 6, and terminals No. 5 and 7 on wire side of A/C control unit connector. Ohmmeter should read 1350-1650 ohms at 77°F (25°C).
3. Using a voltmeter, measure voltage between terminals No. 2 and 3 on wire side of A/C control unit connector. With A/C switch in the ON position, voltmeter should read approximately 12 volts. Turn A/C switch to the OFF position. Measure voltage between terminals No. 2 and 8. Voltmeter should read zero volt.
4. Using an ohmmeter, check continuity between terminals No. 3, 4, 8 and ground. Continuity should exist.
5. Using a voltmeter, measure voltage between terminals No. 3 and 9. With engine coolant temperature at 172°F (78°C), voltmeter should read 12 volts. With engine temperature at 185°F (85°C), check voltage between terminals No. 8 and 9. Voltmeter should read zero volt.
6. Turn ECONO switch to ON position, measure voltage between terminals No. 3 and 10. Voltmeter should read 12 volts. Turn ECONO switch to OFF position. Measure voltage between terminals No. 8 and 10. Voltmeter should read zero volt.
7. If ohmmeter and voltmeter readings are within specification, replace A/C control unit.

Scheme 23

Scheme 24

See also:
• EMISSION SYSTEMS & SUB-SYSTEMS