Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSPLYMOUTH1990LASER RS, 2.0 R, STANDARDREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS - SYSTEM/COMPONENT TESTSMISCELLANEOUS CONTROLSA/C CONTROL UNIT
1990 Plymouth Laser RS, 2.0 R, Standard
A/C Control Unit
1990 Plymouth Laser RS, 2.0 R, StandardSECTION A/C Control Unit
- A/C switch is located above A/C-heater unit. See Fig 1
. Disconnect A/C control unti 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.NOTE: Refer to Fig 2 during the following testing procedure.
- Using an ohmmeter, measure resistance on wire side of A/C control unit connector terminals No. 1 and 6. Also, measure resistance at terminals No. 1 and 6. Also, measure resistance at terminals No. 5 and 7. Ohmmeter should read 1350-1650 ohms at 77°F (25°C).
- Using a voltmeter, measure voltage on wire side of A/C control unit connector terminals No. 2 and 3. With A/C switch in the ON position, voltmeter should read approximately 12 volts. Turn A/C switch to the OFF position. Measure voltage at terminals No. 2 and 8. Voltmeter should read 0 volts.
- Using an ohmmeter, check continuity at terminals No. 3, 4, 8 and ground. Ohmmeter should indicate continuity.
- Using a voltmeter, measure voltage at terminals No. 9 and 3. With engine coolant temperature at 172°F (78°C), voltmeter should read 12 volts. With engine temperature at 185°F (85°C), check voltage at terminals No. 9 and 8. Voltmeter should read 0 volts.
- Turn ECONO swithc to ON position, measure voltage at terminals No. 10 and 3. Voltmeter should read 12 volts. Turn ECONO switch to OFF position. Measure voltage at terminals No. 10 and 8. Voltmeter should read 0 volts.
- If ohmmeter and voltmeter readings are within specification, replace A/C control unit.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.