Section 01-10: Seats and Tracks
1994 Mustang Workshop Manual
DIAGNOSIS AND TESTING

Pinpoint Tests

 

PINPOINT TEST A: POWER SEAT COMPLETELY INOPERATIVE

 

A1 CHECK SUPPLY AND GROUND  

Yes
GO to A6.

No
GO to A2.

 

A2 CHECK GROUND CONTINUITY

Yes
GO to A3.

No
SERVICE open in Circuit 57 (BK). RESTORE vehicle. REPEAT A1.

 

A3 CHECK SUPPLY

  • Measure voltage between Pin 7 Circuit 51 (BK/W) and a known good ground.
  • Is voltage 10 volts or more?
Yes
GO to A6.

No
GO to A4.

 

A4 CHECK SUPPLY SHORT TO GROUND

  • Measure resistance between Pin 7 Circuit 51 (BK/W) and a known good ground.
  • Is resistance 100k ohms or more?
Yes
GO to A5.

No
SERVICE short to ground Circuit 51 (BK/W). RESTORE vehicle. RETEST system.

 

A5 CHECK SUPPLY CIRCUIT CONTINUITY

  • Check continuity of Circuit 51 (BK/W) between power seat connector Pin 7 and Circuit 171 (BK/W) at in-line circuit breaker.
  • Is resistance less than 5 ohms?
Yes
REPLACE in-line circuit breaker. GO to A6.

No
SERVICE open in Circuit 51 (BK/W). RESTORE vehicle. RETEST system.

 

A6 CHECK SWITCH CIRCUIT OPERATION

  • Using a jumper wire jump Circuit 51 (BK/W) Pin 7 to appropriate circuits using chart below.
  • Observe operation of seat as jumper is applied.





    Pin Number Circuit Circuit Function
    1 — Not Used
    2 980 (R/W) Seat Moves Rearward
    3 — Not Used
    4 979 (R/BL) Seat Moves Downward
    5 57 (BK) Ground
    6 978 (Y/BL) Seat Moves Upward
    7 51 (BK/W) Supply
    8 981 (Y/W) Seat Moves Forward
    9 — Not Used

  • Did seat operate properly?
Yes
REPLACE power seat switch. RESTORE vehicle. RETEST system.

No
GO to A7.

 

A7 CHECK SWITCH OUTPUT CIRCUITS FOR SHORT TO GROUND

  • Measure resistance between pins given below and a known good ground.

    SEAT REGULATOR CONTROL SWITCH
    Pin Number Circuit Circuit Function
    1 — Not Used
    2 980 (R/W) Seat Moves Rearward
    3 — Not Used
    4 979 (R/BL) Seat Moves Downward
    5 57 (BK) Ground
    6 978 (Y/BL) Seat Moves Upward
    7 51 (BK/W) Supply
    8 981 (Y/W) Seat Moves Forward
    9 — Not Used

  • Is resistance 100k ohms or more?
Yes
GO to A8.

No
SERVICE suspect circuit for short to ground. RESTORE vehicle. RETEST system.

 

A8 CHECK SEAT REGULATOR MOTOR OPERATION

  • Disconnect seat regulator motor connector.
  • Using jumper wire connected to battery positive, connect the other end to the appropriate pin per chart below.
  • Using a second jumper wire, connect one end to appropriate pin per chart, connect other end to a known good ground.





    Pin Circuit Battery (+) Pin Circuit Ground (-) Seat Function
    1 980 (R/W) 2 981 (Y/W) Seat Moves Rearward
    2 981 (Y/W) 1 980 (R/W) Seat Moves Forward
    3 978 (Y/BL) 4 979 (R/BL) Seat Moves Upward
    4 979 (R/BL) 3 978 (Y/BL) Seat Moves Downward

  • Reverse jumper wires per chart and observe motor operation.
  • Did seat regulator motor operate correctly?
Yes
GO to A9.

No
REPLACE power seat regulator motor and transmission assembly. RESTORE vehicle. RETEST system.

 

A9 CHECK POWER SEAT CIRCUIT CONTINUITY

  • Using an ohmmeter, check each circuit from power seat regulator motor connector to power seat regulator control switch connector.
  • Is resistance 5 ohms or less?
Yes
Power seat system OK. RESTORE vehicle. RETEST system.

No
SERVICE suspect circuit for open. RESTORE vehicle. RETEST system.

 

PINPOINT TEST B: FORWARD/BACKWARD SLIDING OPERATION DOES NOT WORK PROPERLY

 

B1 CHECK POWER SEAT REGULATOR MOTOR FORWARD/BACKWARD OPERATION  

  • Disconnect power seat regulator motor connector.
  • Using a jumper wire connected to battery positive, connect the other end to appropriate pin per chart, connect other end to a known good ground.





    Pin Circuit Battery (+) Pin Circuit Ground (-) Seat Function
    1 980 (R/W) 2 981 (Y/W) Seat Moves Rearward
    2 981 (Y/W) 1 980 (R/W) Seat Moves Forward
    3 978 (Y/BL) 4 979 (R/BL) Seat Moves Upward
    4 979 (R/BL) 3 978 (Y/BL) Seat Moves Downward

  • Reverse jumper wires per chart and observe motor operation.
  • Did seat move properly?
Yes
LEAVE jumper wires connected to supply and ground, being careful not to touch them together. GO to B2.

No
REPLACE power seat regulator motor and transmission assembly. RESTORE vehicle. RETEST system.

 

B2 CHECK POWER SEAT FORWARD/BACKWARD CIRCUITS

  • Reconnect power seat regulator motor .
  • Remove seat back control switch and housing as outlined.
  • Connect jumper wires to pins per chart below.





    Pin Circuit Battery (+) Pin Circuit Ground (-) Seat Function
    2 980 (R/W) 8 981 (Y/W) Seat Moves Rearward
    4 979 (R/BL) 6 978 (Y/BL) Seat Moves Downward
    6 978 (Y/BL) 4 979 (R/BL) Seat Moves Upward
    8 981 (Y/W) 2 980 (R/W) Seat Moves Forward

  • Reverse jumper wires per chart and observe seat operation.
  • Did seat move properly?
Yes
REPLACE power seat back control switch and housing . RESTORE vehicle. RETEST system.

No
SERVICE suspect circuit for open. RESTORE vehicle. RETEST system.

 

PINPOINT TEST C: UP/DOWN LIFTING OPERATION DOES NOT WORK PROPERLY

 

C1 CHECK POWER SEAT MOTOR UPWARD/DOWNWARD OPERATION  

  • Disconnect seat regulator motor connector.
  • Using a jumper wire connected to battery positive, connect the other end to appropriate pin per chart below.
  • Using a second jumper wire, connect one end to appropriate pin per chart, connect other end to a known good ground.





    Pin Circuit Battery (+) Pin Circuit Ground (-) Seat Function
    1 980 (R/W) 2 981 (Y/W) Seat Moves Rearward
    2 981 (Y/W) 1 980 (R/W) Seat Moves Forward
    3 978 (Y/BL) 4 979 (R/BL) Seat Moves Upward
    4 979 (R/BL) 3 978 (Y/BL) Seat Moves Downward

  • Reverse jumper wires per chart and observe motor operation.
  • Did seat move properly?
Yes
LEAVE jumper wires connected to supply and ground being careful not to touch them together. GO to C2.

No
REPLACE power seat regulator motor and transmission. RESTORE vehicle. RETEST system.

 

C2 CHECK POWER SEAT REGULATOR MOTOR LIFTING CIRCUITS

  • Reconnect power seat regulator motor .
  • Remove seat back control switch and housing as outlined.
  • Connect jumper wires to pins per chart below.





    Pin Circuit Battery (+) Pin Circuit Ground (-) Seat Function
    2 980 (R/W) 8 981 (Y/W) Seat Moves Rearward
    4 979 (R/BL) 6 978 (Y/BL) Seat Moves Downward
    6 978 (Y/BL) 4 979 (R/BL) Seat Moves Upward
    8 981 (Y/W) 2 980 (R/W) Seat Moves Forward

  • Reverse jumper wires per chart and observe seat operation.
  • Did seat move properly?
Yes
REPLACE power seat back control switch and housing . RESTORE vehicle. RETEST system.

No
SERVICE suspect circuit for open. RESTORE vehicle. RETEST system.

 

PINPOINT TEST D: POWER LUMBAR SUPPORT/BOLSTER DOES NOT WORK PROPERLY

 

D1 CHECK SUPPLY AND GROUND  

  • Remove seat back control switch and housing as outlined.
  • Connect a test lamp between Circuit 517 (BK/W) Pin 1 and a known good ground.
  • Did test lamp illuminate?
Yes
GO to D5.

No
GO to D2.

 

D2 CHECK SUPPLY FOR SHORT TO GROUND

  • Measure resistance between Circuit 517 (BK/W) Pin 1 and a known good ground.
  • Is resistance 100k ohms or more?
Yes
GO to D3.

No
SERVICE short to ground Circuit 517 (BK/W). RESTORE vehicle. RETEST system.

 

D3 CHECK SUPPLY CIRCUIT CONTINUITY

  • Check continuity from Circuit 517 (BK/W) Pin 1 at seat back control switch and housing to Circuit 171 (BK/W) at in-line circuit breaker.
  • Is resistance 5 ohms or less?
Yes
REPLACE in-line circuit breaker. GO to D4.

No
SERVICE open Circuit 517 (BK/W). RESTORE vehicle. RETEST system.

 

D4 CHECK SWITCH OPERATION

  • Connect test lamp to Circuit 490 (R) Pin 2 and a known good ground.
  • Actuate seat back control switch and housing to inflate position.
  • Did test lamp illuminate?
Yes
GO to D5.

No
REPLACE seat back control switch and housing . RESTORE vehicle. RETEST system.

 

D5 CHECK FRONT SEAT BACK PAD ADJUSTING PUMP

  • Actuate seat back control switch and housing to the inflate position.
  • Did front seat back pad adjusting pump run?
Yes
GO to D9.

No
GO to D6.

 

D6 CHECK FRONT SEAT BACK PAD ADJUSTING PUMP SUPPLY AND GROUND

  • Disconnect front seat back pad adjusting pump .
  • Connect one lead of voltmeter to Circuit 490 (R) Pin 1 of harness connector. Connect other lead of voltmeter to Circuit 57 (BK) Pin 2 of harness connector.
  • Did voltmeter show battery voltage?
Yes
REPLACE front seat back pad adjusting pump . RESTORE vehicle. RETEST system.

No
GO to D7.

 

D7 CHECK FRONT SEAT BACK PAD ADJUSTING PUMP SUPPLY

  • Connect test lamp to Circuit 490 (R) and a known good ground.
  • Actuate seat back control switch and housing to inflate position.
  • Did test lamp illuminate?
Yes
SERVICE open in Circuit 57 (BK). RESTORE vehicle. RETEST system.

No
GO to D8.

 

D8 CHECK FRONT SEAT BACK PAD ADJUSTING PUMP SUPPLY CIRCUIT FOR SHORT TO GROUND

  • Check continuity of Circuit 490 (R) Pin 1 to Circuit 490 (R) Pin 1 at motor connector.
  • Is resistance 5 ohms or less?
Yes
REPLACE seat back control switch and housing . RESTORE vehicle. RETEST system.

No
SERVICE open in Circuit 490 (R). RESTORE vehicle. RETEST system.

 

D9 CHECK FRONT SEAT BACK PAD ADJUSTING SYSTEM

  • Actuate seat back control switch and housing to inflate position.
  • Observe front seat back pad adjuster .
  • Did front seat back pad adjuster inflate?
Yes
GO to D13.

No
GO to D10.

 

D10 CHECK FRONT SEAT BACK PAD ADJUSTER

  • Gain access to front seat back pad adjuster as outlined.
  • Inspect front seat back pad adjuster .
  • Is there any visible damage to the front seat back pad adjuster ?
Yes
SERVICE as necessary. RESTORE vehicle. RETEST system.

No
GO to D11.

 

D11 CHECK FRONT SEAT BACK PAD ADJUSTING PUMP

  • Disconnect hose from front seat back pad adjusting pump . Actuate front seat back pad adjusting pump with seat back control switch and housing .
  • Is front seat back pad adjusting pump pumping air?
Yes
RECONNECT hose. GO to D12.

No
REPLACE front seat back pad adjusting pump . RESTORE vehicle. RETEST system.

 

D12 CHECK FRONT SEAT ADJUSTING MOTOR DRIVE TUBE

  • Actuate seat back control switch and housing to inflate position.
  • Disconnect front seat adjusting motor drive tube at front seat back pad adjuster .
  • Is there air being pumped to the front seat back pad adjuster ?
Yes
REPLACE front seat adjusting motor drive tube . GO to D13.

No
REPLACE seat back control switch and housing . RESTORE vehicle. RETEST system.

 

D13 CHECK LUMBAR SUPPORT AIR EXHAUST

  • Actuate seat back control switch and housing to the deflate position.
  • Does front seat back pad adjuster deflate?
Yes
Front seat back pad adjuster OK. RESTORE vehicle.

No
REPLACE seat back control switch and housing . RESTORE vehicle. RETEST system.