Bench Testing
Bench testing of both the inside and the driver side outside mirrors can be done if proper care is exercised. Connect the inside mirror ground terminal pin to ground and the fused ignition switch output (run-start) terminal pin to 12 volts. The inside mirror can now be tested by completely blocking the ambient photocell (forward-facing) light sensor and shining a light into the headlight photocell (rearward-facing) light sensor.
In the following test, 1.2 volts is applied to the outside mirror dimming circuits. DO NOT apply 12 volts to these circuits or the mirror dimming circuitry will be damaged and require replacement.
For an outside mirror, there are two pigtail wire circuits (auto day/night mirror plus and auto day/night mirror minus) that are normally controlled by the outputs from the inside mirror circuitry. Applying 1.2 volts to these two circuits should cause the outside mirror glass to darken. If the mirror glass does not darken, the entire mirror glass and case assembly can be replaced just as it is when the glass has been broken.