1990 Subaru Legacy L, Battery Goes Dead

This 1990 Subaru Legacy L came in with the complaint that the battery would go dead while the vehicle sat for a couple of days. This little Subaru had been to two other shops including a dealership without having the problem resolved. The battery had been replaced three times and the seat belt retractor motors had been disconnected.  I connected my multimeter amp leads in series between the battery negative post and the battery negative cable end. There was a nominal .30 amp draw even after letting the system sit for an hour. None of the test accessible fuses in the underhood fuse box showed any sign of a drain.


Moving to the dash fuse box under the driver’s side of the dash …


…I removed the cover to access the fuses for testing.


The 20 amp fuse in the dead center of the fuse box indicated  a current flow…


…of .80 millivolts.  Removing the 20 amp power door lock fuse also removed the .30 amp drain on the battery. Knowing that there was a problem in the power door lock system and that my testing up until this point had been done with the doors unlocked I decided to lock the doors and check the result. The drain went away. My thinking at this point was that there was a problem in a solid state module. The only issue with that train of thought was that according to the wiring diagram there are only four actuators and one switch. No modules in the system.  Then my thought process changed to bent linkage inside the driver’s door.


To access the linkage and the single switch, the door panel has to be removed. There are three phillips headed screws at the lower front corner of the door panel that have to be removed.


The interior door handle trim panel is held in place by three locking tabs. One under the handle as shown below and one above the handle in the same general area.


Then the trim panel needs to be pushed slightly towards the front of the door to release the third clip.


Then the cover shown below has to be removed to access the screw behind it.



There may or may not be a piece of foam that has to be removed in order to access yet another phillips headed screw.



This triangular panel needs to be removed either grabbing or prying at the upper end and pulling it loose from the door.



Then the door panel can be grabbed and the lower front edge and pulled loose from the door. Working around the edge to loosen all of the push pin clips. After the edges are loose the door panel can be lifted up and then off of the door.  Looking down at the inside of the door panel the power window switch assembly can be disconnected.


This door panel has been off several times and there was sticky black adhesive all over the place. I had to carefully pull the vapor barrier loose at the lower rear corner, roll it forward and secure it in place with tape to keep the sticky adhesive from going everywhere.


After following the wiring harness down and reaching inside the door I was able to disconnect the power door lock switch. I did remove the switch and door latch assembly thinking that I would find some sort of damage that was causing the battery drain issue but after careful examination I determined that the linkage and the switch were not the problem. By the way the drain was also gone with the switch disconnected.


Instead I turned my attention to testing the circuits going into the power door lock switch. The red wire has power at all times and is supplied by the power door lock fuse. There is supposed to be a constant ground on the red/yellow wire. All other wires are supposed to read open. Meaning no continuity to ground or power. I found a ground circuit on the black wire. Looking at the wiring diagram I realized that the black wire attaches to each of the door lock actuators. Internally each actuator has a blocking diode built in to the circuitry. I removed all of the door panels and disconnected all three of the door lock actuators. The driver’s door on this model does not have an actuator. It relies on the movement of either the key or the interior door lock handle to actually lock and unlock the door with a mechanical linkage.  My drain was still there and it had me scratching my head until the light bulb went off and I remembered that the tailgate also has a lock actuator. After disconnecting that actuator the drain was gone.


I called the dealership to order a new actuator and found out that it was only supplied as the latch and actuator assembly. However it was no longer available. I searched high and low and finally found a new actuator by itself as a Airtex/Wells part number DLA598. Do not confuse it with a SMP / Standard Motor Products part number DLA598. The SMP part fits a Dodge application and not a Subaru.  It is listed as a right front door lock actuator for a USA model Legacy L. I think I may have bought the very last one in existence. As a final note I took the old actuator apart in order to replace what I thought would be a faulty diode. The diode tested as being good. I also found a capacitor also installed in the actuator. To get the actuator apart I wound up having to damage the electrical socket portion since it was designed to be assembled one time and not to be taken apart. If I had not been able to find a replacement the repair of the battery drain would have been to simply disconnect the tailgate door lock actuator.

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