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Home >> Jeep >> 1999 >> Grand Cherokee Laredo, 4.0 S, AWD >> Repair and Diagnosis >> Body & Frame >> Body, Cab Control Systems >> Body Control Computer - Tests >> Windshield Wiper/Washer System Symptom Tests >> Wiper Operates Constantly With Ignition On

Wiper Operates Constantly With Ignition On

  1. Replace wiper on/off relay in Power Distribution Center (PDC) with known good relay. If wipers operate correctly, replace wiper on/off relay. If wipers do not operate, go to next step.
  2. Turn ignition off. Remove wiper high/low relay and on/off relay in Power Distribution Center (PDC). Using voltmeter, measure voltage between ground and terminal No. 30 (Yellow/Dark Green wire) on wiper high/low relay socket. If voltage is greater than 10 volts, repair Yellow/Dark Green wire for short to voltage. If voltage is 10 volts or less, go to next step.
  3. Disconnect wiper motor connector. Turn ignition on. Measure voltage between ground and terminal No. 87A (Brown/White wire) on wiper high/low relay socket. If voltage is greater than 10 volts, repair Brown/White wire for short to voltage. If voltage is 10 volts or less, go to next step.
  4. Measure voltage between ground and terminal No. 87 (Red/Yellow wire) on wiper high/low relay socket. If voltage is greater than 10 volts, repair Red/Yellow wire for short to voltage. If voltage is 10 volts or less, go to next step.
  5. Using ohmmeter, measure resistance between ground and terminal No. 85 (Black wire) on wiper on/off relay socket. If resistance is less than 5 ohms, repair Black wire for short to ground. If resistance is 5 ohms or greater, go to next step.
  6. Ensure ignition is off. Connect test light to terminals No. 85 and 86 on wiper on/off relay from Power Distribution Center (PDC). Turn ignition on. Using scan tool, actuate wiper relay. If test light pulses, test is complete. If test light does not pulse, replace Body Control Module (BCM).
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