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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 725 (Door System, Mirror System & Window System) >> Diagnostic Information and Procedures >> Mirrors - Outside Automatic Day-Night Feature Inoperative >> Diagnostic Aids

Diagnostic Aids

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The automatic day-night feature of the driver outside rearview mirror may be inoperative due to the signal circuit being shorted to battery positive voltage. When this condition occurs, both the driver outside rearview mirror and the inside rearview mirror will be in a darkened state. Both mirrors will be permanently damaged and will need to be replaced.

Mirrors - Outside Automatic Day-Night Feature Inoperative

Step Action Value(s) Yes No
Schematic Reference:  Outside Mirror Schematics  
1 Did you review the description and operation of the automatic day-night feature of the driver outside rearview mirror? - Go to Step 2  Go to Symptoms - Doors 
2
  1. Turn ON the ignition, with the engine OFF.
  2. Turn ON the automatic day-night feature of the inside rearview mirror.
  3. Cover the sensor on the back of the inside rearview mirror.
  4. Shine a bright light into the sensor on the face of the inside rearview mirror.
Does the inside rearview mirror darken?
- Go to Step 3  Go to MIRRORS - AUTOMATIC DAY-NIGHT INOPERATIVE
3 While shining a bright light into the sensor on the face of the inside rearview mirror, observe the driver outside rearview mirror.
Does the driver outside rearview mirror darken?
- Go to TESTING FOR INTERMITTENT AND POOR CONNECTIONS Go to Step 4 
4
  1. Turn OFF the ignition.
  2. Disconnect the harness connector of the driver outside rearview mirror.
  3. Turn ON the ignition, with the engine OFF.
  4. Turn ON the automatic day-night feature of the inside rearview mirror.
  5. Cover the sensor on the back of the inside rearview mirror.
  6. Shine a bright light into the sensor on the face of the inside rearview mirror.
  7. Measure the voltage between the signal circuit and the low reference circuit of the driver outside rearview mirror.
Is the voltage within the specified range?
0.75-1.5 V Go to Step 9  Go to Step 5 
5 Is the voltage greater than the specified value? 1.5 V Go to Step 11  Go to Step 6 
6 Measure the voltage between the signal circuit of the driver outside rearview mirror and a good ground.
Is the voltage within the specified range?
0.75-1.5 V Go to Step 8  Go to Step 7 
7 Test the signal circuit of the driver outside rearview mirror for an open or short to ground. Refer to CIRCUIT TESTING and WIRING REPAIRS .
Did you find or correct the condition?
- Go to Step 14  Go to Step 10 
8 Test the low reference circuit of the driver outside rearview mirror for an open or high resistance. Refer to CIRCUIT TESTING and WIRING REPAIRS .
Did you find or correct the condition?
- Go to Step 14  Go to Step 10 
9 Inspect for poor connections at the harness connector of the driver outside rearview mirror. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS and CONNECTOR REPAIRS .
Did you find or correct the condition?
- Go to Step 14  Go to Step 12 
10 Inspect for poor connections at the harness connector of the inside rearview mirror. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS and CONNECTOR REPAIRS .
Did you find or correct the condition?
- Go to Step 14  Go to Step 13 
11
IMPORTANT: A short to battery positive voltage on the signal circuit of the driver outside rearview mirror will cause permanent damage to both the driver outside rearview mirror face and the inside rearview mirror.
Repair the short to voltage in the signal circuit of the driver outside rearview mirror. Refer to WIRING REPAIRS .Did you complete the repair?
- Go to Step 14  -
12 Replace the driver outside rearview mirror. Refer to Mirror Replacement (Power Mirror)  or Mirror Replacement (Manual) .
Did you complete the replacement?
- Go to Step 14  -
13 Replace the inside rearview mirror. Refer to REARVIEW MIRROR REPLACEMENT .Did you complete the replacement? - Go to Step 14  -
14 Operate the system in order to verify the repair.
Did you correct the condition?
- System OK Go to Step 2