Section 01-14: Handles, Locks, Latches and Mechanisms
1993 Mustang Workshop Manual
DIAGNOSIS AND TESTING

Relay

There is no relay test for the 2-door models. Power is supplied directly to the door lock motor through the door lock switch except in keyless entry equipped vehicles which have power door lock relays located in the keyless entry module, located on the underside of the rear package tray.

Refer to the following Diagnosis Charts when servicing the power door locks and switches.

NOTE: Before starting electrical diagnosis, check for mechanical binds by manually operating the door locks. Then, operate lock system several times from each switch, while observing the operation of all door locks. Be sure battery is fully charged.

ConditionPossible SourceAction
  • One Door Lock Does Not Work
  • Latch or linkage binding.
  • Using Multi-Purpose Grease D7AZ-19584-AA (ESR-M1C159-A and ESB-M1C106-B) or equivalent, spray into latch opening and manually cycle ten times. Check for interference around night latch and all linkage.
 
  • Open or shorted circuit.
  • Check for voltage at actuator connector, operating switch in both positions. Service circuit if necessary.
 
  • Malfunctioning actuator.
  • Test actuator. Replace if necessary.
  • All Door Locks Do Not Work
  • Malfunctioning circuit breaker.
  • Check circuit breaker. (Refer to Section 18-01.) Replace if necessary.
 
  • Open or shorted circuit.
  • Check wiring and connections between circuit breaker and door lock switches. Service if necessary.
  • All Locks Work From One Switch Only
  • Open or shorted circuit.
  • Check wiring and connections between circuit breaker and inoperative switch. Service if necessary.
 
  • Malfunctioning switch.
  • Test actuator. Replace if necessary.
  • Door Locks Operate One Way Only
  • Open or shorted circuit.
  • Check wiring and connections between door lock switches and motors. Service if necessary.
 
  • Malfunctioning switch.
  • Test actuator. Replace if necessary.
 
  • Open ground circuit.
  • Check ground circuit from LH switch. Service if necessary.
  • Door Locks Work With Engine Running Only
  • Low charge in battery.
 
  • Loose or corroded connections.
  • Check wiring and connections. Service if necessary.
 
  • Latch or linkage binding.
  • Using Multi-Purpose Grease D7AZ-19584-AA (ESR-M1C159-A and ESB-M1C106-B) or equivalent, spray into latch opening and manually cycle ten times. Check for interference around night latch and all linkage.
  • Locks Do Not Work In Below Freezing Weather
  • Frozen door latch or linkage.
  • Bring vehicle into heated garage to allow lock system to thaw. Verify that all locks now work. Using Multi-Purpose Grease D7AZ-19584-AA (ESR-M1C159-A and ESB-M1C106-B) or equivalent, spray into latch opening and manually cycle ten times. May be necessary to remove door trim panel to lubricate entire latch and linkage system. Refer to Section 01-05.
  • Locks Work Intermittently
  • Loose connections.
  • Check connectors. Secure if necessary.
 
  • Poor ground at LH switch.
  • Check ground circuit from LH switch. Service if necessary.
 
  • Malfunctioning switch.
  • Test switch. Replace if necessary.