Hello:

I have a 1992 SC400 that has been having some battery trouble. After sitting overnight, the car will not start. So far, it has cranked after my 8 hour work days but by that time the battery is clearly weakened. I took the battery to be load tested and it failed. The result was 550CCA of 700CCA (the battery is 3 years old).

Before I purchased a new battery, I decided to take it home and use my multimeter to test for a parasitic drain. The battery measures 12.4-12.5V. When running, it measures 13.6V meaning the alternator is doing its job.

I then did the parasitic drain test by removing the battery cable and putting the multimeter in to measure draw with the engine and all accessories off. The draw was consistently .459A...I then started pulling fuses and when I got to the "DOME" 10A fuse the draw dropped immediately to .023 or 23mA (which I understand is within acceptable range).

I made sure no lights were left on etc, etc and even closed my wife in the trunk so she could confirm the trunk light was going off. Has anyone experienced this and have any suggestions on where to start? Anyone have a wiring diagram for the DOME circuit? I can confirm that it controls the in-dash clock, green foot light, dome lights, steering wheel adjustment and cigarette lighter.

Also, is the .5A draw enough to pull my weakened battery down overnight? I'm afraid something else may be coming on at random times that I haven't caught with the multimeter. I have kept the battery hooked up to a 2A trickle charge over night to get me to/from work.

Side note: not sure if this could be related but when the car doors are open the doors sometimes "unlock" themselves over and over again as if I'm pushing the key FOB. Hasn't bothered me before because it doesn't lock them and doesn't do it when the door is closed.

Thanks in advance for any advice.

 

How did you talk your wife into the trunk?
Great one!

 

It seemed more entertaining than feeling if the bulb was hot.

 

LMAO! So did you let her out yet?

Um, have you checked for shorts in the door wiring yet? If they do strange things when open, you may have a wire that is pinched or has worn through the insulation and is contacting with the door open.

 

Ok, I will check that out. I have to remove the door panel to fix the window regulator anyways

More info: I put the fuse back in yesterday to set the steering wheel position and then pulled it again. Since then several strange things have happened. 1. The clock somehow came back on but it is way more dim than anything else and doesn't count. 2. The orange needle on the speedo has blinked to life a couple of time which has never happened. 3. The speedo itself has actually worked which hasn't happened consistently in years. 4. The trip-meter counts as normal but resets every time the car is turned off.

Besides that, the car has started fine every morning since I pulled the DOME fuse. Glad I didn't buy a new battery.