SYS.OK|MANUAL.DB● LIVE
HOMESERVICE MANUALSFORD1987THUNDERBIRD BASE, 3.8 3REPAIR AND DIAGNOSIS (SINGLE PAGE)ACCESSORIES & EQUIPMENTANTI-THEFT SYSTEMSKEYLESS ENTRY SYSTEMTESTINGTEST C - KEYPAD INPUTTEST PROCEDURES
1987 Ford Thunderbird Base, 3.8 3

Test Procedures

1987 Ford Thunderbird Base, 3.8 3SECTION Test Procedures
  1. Disconnect keypad and Brown connector. Determine which button is malfunctioning. See KEYPAD INPUT TEST  table. Check appropriate pin/circuit for a short to ground between keypad and Brown connector. If short is found, go to step 3). If no short is found, go to next step.
  2. With Brown connector disconnected, check for short between malfunctioning button and pin No. 12 in Brown connector. See Keyless Entry Module Connector Terminal Identification in TEST A  . If no short is found, go to step 4). If short is found, replace keypad and repeat QUICK TEST  .
    KEYPAD INPUT TEST

    Key Circuit No. Pin No.
    "1/2" 78 3
    "3/4" 79 4
    "5/6" 121 5
    "7/8" 122 6
    "9/0" 123 7
  3. Remove door trim panel. Disconnect keypad connector. Check circuit that corresponds to malfunctioning button for resistance of less than 100,000 ohms between keypad connector and ground, and then at pin No. 12 in Brown connector. If resistance to ground or at pin No. 12 is low, replace switch. If resistance is not low, repair harness between Brown connector and keypad connector. Repeat QUICK TEST  .
  4. With "1/2" button depressed, verify that wire between pin No. 12 of Brown connector and pin No. 3 of keypad connector is not open or shorted to ground. If wire is okay, go to next step. If not, repair open or short in wire and repeat QUICK TEST  .
  5. Connect Brown connector. Connect voltmeter between pin No. 1 of Brown connector and ground. For each button that failed to light on keypad, connect a jumper wire for 5 seconds between pin No. 12 of Brown connector and keypad pins No. 3 through 7. If readings are 5 volts or more, go to next step. If not, replace keyless entry module and repeat QUICK TEST  .
  6. Remove door trim panel. Disconnect keypad connector. On Town Car, check resistance between pins No. 3 and 6 of keypad. On all other models, check resistance between pins No. 1 and 8 of keypad. If reading is 10 ohms or more, replace keypad and repeat QUICK TEST  . If reading is less than 10 ohms, go to next step.
  7. Check continuity between all pins in keypad until all pin pairs have been checked. On Town Car, continuity should exist between pins No. 3 and 6; all other pin pairs should not. On all other models, continuity should exist between pins No. 1 and 8; all other pin pairs should not exhibit continuity. If okay, go to next step. If shorts are found, replace keypad and repeat QUICK TEST  .
  8. Check continuity between pins No. 2 and 5 of keypad connector. Repeat procedure for each key (in turn), checking continuity between corresponding pin and pin No. 5 of keypad connector. See the KEYPAD INPUT TEST  table. If continuity exists, repair open or short in wiring of non-functional button(s). If no continuity exists, replace keypad and repeat QUICK TEST  .
RENDER: 1.0x

NO RELATED

Recommended Tools & Savings

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Affiliate disclosure: We may earn a commission at no extra cost to you.

Shop Manual-Ready ToolsFree Quote CheckQuote Shield Pro

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.