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Home >> Lincoln >> 2009 >> Navigator RWD >> Repair and Diagnosis >> Electrical >> Gauges >> Instrument Cluster Illumination & Instrument Panel Illumination >> Diagnosis And Testing >> Instrument Cluster and Panel Illumination >> Pinpoint Tests >> Pinpoint Test A: All The Dimmable Illumination Is Inoperative >> Normal Operation

Normal Operation

The Smart Junction Box (SJB) sends a voltage reference signal to the instrument panel dimmer switch through circuit CLN27 (WH/BN). The signal is routed through a variable resistor within the instrument panel dimmer switch and then back to the SJB  through circuit RLN29 (WH/OG) to an internal ground. The reference voltage changes depending on the position of the dimmer switch. When the dimmer switch is in the lowest setting, the resistance is low. When the SJB  senses the voltage is low (switch in the lowest setting), the dimmable backlighting intensity is low. When the SJB  senses the voltage reference is high (switch in the highest setting), the dimmable backlighting intensity is bright. The signal should be within a range (depending on the switch position) that the SJB  monitors. If the signal is too high (an open circuit or short to voltage), the SJB  faults the dimmable backlighting to full nighttime brightness. If circuit CLN27 (WH/BN) is short to ground, the SJB  interprets this as the lowest setting and sets the backlighting to the lowest intensity level, appearing to be inoperative.

Based on input received from the instrument panel dimmer switch, the SJB  sends a message over the network to the backlight modules indicating the backlighting intensity level and a pulse-width modulated voltage to the hardwired dimmable illumination sources through circuit VLN04 (VT/GY) (Navigator only) and/or circuit VLN18 (BU/WH) (Expedition) (Navigator auxiliary climate control assembly).

This pinpoint test is intended to diagnose the following: 

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