ATC Head Illumination Inoperative
NOTE:
After making any repairs, perform BODY VERIFICATION TEST
under VERIFICATION TESTS.
Possible Causes:
- Identify ATC Head Illumination Problem
- Ground Circuit Open
- Panel Lamps Feed Circuit Open
- ATC Head - Illumination Inoperative
Testing
- Turn the park lights on and observe the ATC head display. If the problem is with the letters and LED lights, replace the automatic temperature control head. See AUTOMATIC A/C-HEATER SYSTEMS - CONCORDE, INTREPID & 300M article in HVAC. If the problem is not with the letters and LED lights, go to next step.
- Turn ignition off. Disconnect ATC head harness connector. See Figure . Turn off all lights. Measure the resistance between ground and the ground circuit (cavity No. 3). If the resistance is 5 ohms or less, go to next step. If the resistance is 5 ohms or more, repair the ground circuit for an open.
- Turn the park lights on. Measure the voltage of the park lights feed circuit. Rotate the dimmer switch thumb wheel and observe the voltage. If the voltage range is less than 3.5 volts to more than 9 volts when the switch is rotated, replace the automatic temperature control head. See AUTOMATIC A/C-HEATER SYSTEMS - CONCORDE, INTREPID & 300M article in HVAC. If not, repair the panel lights feed circuit for an open.
NOTE:
This step checks the background lights.