1986 Mercury Sable LS, 4D SedanFACTORY OEM SERVICE PROCEDURE

Test Procedures

  1. Disconnect Brown connector and keypad connector. Determine which button has failed and check appropriate circuit for a short to ground between keypad and Brown connector. If short is located, go to step 3) and repeat Quick Test. If okay, go to next step.
  2. Reconnect keypad connector and check for short between appropriate pin and pin 12 in Brown connector. If okay, go to step 4). If short is found, replace keypad and repeat Quick Test.
  3. Remove door trim. Disconnect keypad connector. Check circuits that correspond to malfunction button for resistance less than infinity between keypad connector and ground or pin 12 in Brown connector. See Figure . If low resistance, replace switch. If no low resistance is found, repair harness between module and keypad connectors and repeat Quick Test.
  4. Ensure circuit between Brown connector pin 12 and keypad connector pin 3 is not broken or shorted to ground with 1/2 button depressed. If okay, go to next step. If not, repair and repeat Quick Test.
  5. Connect Brown connector to module. Insert voltmeter lead into back of Brown connector at pin 1, then connect other lead to ground. Momentarily connect a jumper wire between pin 12 in back of Brown connector and pins 3 and 7 for malfunctioning button. At least 5 volts should register on voltmeter for 5 seconds. If not, replace module and repeat Quick Test. If so, go to next step.
  6. Remove door trim and disconnect keypad from connector. Check resistance between pins 8 and 1 of keypad. If more than 10 ohms, replace keypad and retest. If under 10 ohms, go to next step.
  7. Check for continuity between each pin in keypad. Pins 8 and 1 should have continuity; all other pairs should not. If shorts are found, replace keypad and repeat Quick Test. If okay, go to next step.
  8. Check for continuity between pin 2 and 5 of keypad connector, with any button depressed. Then check between each pin and pin 2 as appropriate button is depressed. See Figure . If continuity is present in all circuits, repair wiring. If continuity is not found when button is depressed, replace keypad and repeat Quick Test.
Factory Service Tools

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.

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