2008 Honda Accord EX-L, 4-door sedan, 4-cycl engine, auto trans.

Bought this car 2 months ago and was told something was draining the battery when the car sat for 2-3 days, requiring it to need jumped to start. So, went in with my eyes open. Battery is 1 1/2 years old, but had it tested at a local parts store and they assured me the battery, alternator and starter were all in great condition.

So, using a fully charged battery, I connect my multi-meter up to check for parasitic draw (red lead to negative battery cable unhooked and black lead to negative battery post). I see a .36 amp draw initially. I start pulling fuses in the engine compartment box and fuse #15 (10 amp) is the culprit. Reading on the meter drops to .02 amps. Those of you familiar with this B-Can fuse listed as "Back Up" know that it provides power to about 2 dozen different items (audio unit, driver's door courtesy light, passenger door courtesy light, gauge control module, HFL system, Navigation system, Immobilizer Keyless Control, Master Power Window driver’s side door switch, Drivers MICU, Passengers MICU, and on and on.......).

Working it from there, I discover that by unplugging the Master Power Window Switch, the reading drops to .03 amps. I have not went any further. I ordered a replacement switch and I have the same issue with it installed. All of the windows and locks worked fine using this switch and also worked with the old switch I just replaced. Have I not went far enough downstream I wonder?

When I initially hook up the meter, the door locks engage and I get a reading of .36 amps. 1 minute and 15 seconds later, this drops to a reading of .26 amps. I assume this is the car going into "sleep mode", but I have read that this should only take 30-40 seconds, so seems longer than usual if correct. When I unplug the wiring harness from the Master Power Windows Switch, it takes 7 minutes before the meter reading drops to .03 amps. Should it take this long? I would think it would be instantly.

So, if you have read all of this - thank you. I am trying to understand if the Master Power Window Switch seems logical to be the root cause of this battery drain, or if I stopped digging prematurely when it appeared to be. If anyone else has disconnected this switch previously, did it take 7 minutes to drop amperage? Since I replaced the switch, this is not something that would have to be reprogramed is it?

 

The cause may be due to a faulty driver's door lock actuator/**** switch (it is part of the door lock actuator assembly). The multiplex system may detect the door is not locked/closed and stay awake.

 

Interesting. Whenever the drivers side door is closed, I hear what may be the door actuator "locking and unlocking" 2-3 times. At first, I thought this was something rattling inside of the door, but when I shake the door, there is no rattle. I've heard the noise since the car was purchased 2 months ago, but whenever I watch the lock on the door after closing it, it doesn't move, so I was not sure what I was hearing.

I did not see a change on the meter when I unplugged the door actuator harness from the door lock actuator. But to be fair, I unplugged it, didn't see a change and plugged it right back in. The Power mirror switch was unplugged for several minutes before I noticed the meter drop, as it was the last thing to check and I took a break before reassembling. That may have been a lucky catch. As mentioned, all windows work fine with this switch and the previous one, so that's part of the head scratching.

 

On any modern vehicle(including Honda) it takes any where from 5 to 60 mins for all of the modules to completely enter "sleep" mode.
Chasing a draw before that allotted time is an exercise in futility.

After 60 mins(or less) the vehicle should not have a draw greater that 50mA(.05a)

 

Update: Took the car to the local Honda dealer and let them plug it in to zero in on the culprit. They replaced the under dash driver's side fuse box. 1 week later and it appears to be good to go. No issues since.

 

Interesting it ended up being the fuse box, but hey at least its fixed. Must have been a short to power or ground in the circuitry of the fuse box.