The customer was having to jump start the car battery even after a relatively short sitting time.
The car battery didn't go down while driving but while sitting.
Those clues would have you thinking of a bad battery as most likely but the battery had been replaced with new and still had the same problem. Next likely would be an excessive drain on the battery while sitting. You have to do some testing and see where it takes you.
Now the car had only been sitting a few minutes since the customer dropped it off but that battery was completely dead when I tried to crank the car. A good battery won't die that quickly even if you leave the key on and all accessories on. The battery will need to be tested.
I did have to use the jumper to start the car. When you are doing electrical system tests you should make sure you have a good battery that is fully charged. I like to use a battery tester that measures internal plate resistance. This requires removal of the battery terminals and direct connection to the battery posts. The tester will output more information but BAD or GOOD is handy too.
I couldn't test the system with this battery so I removed it and replaced it with a known good battery from my stock for testing purposes. After connecting the new battery I have to wait until enough time has passed for modules on the car to "time out". Test for a draw too soon and you could be tracing a problem that is a perfectly normal condition. Waiting time varies. I've waited as long as 3 hours on some Fords and as little as 0 minutes on others for normal draw to shut off. I use 50mA as the magic number just because most use that as the spec. If I'm under 50mA draw then there is either no drain problem or it is intermittent and not present at this time. This car had a battery draw problem.
With a reading like that I wanted to see if anything was obviously turned on. I'm looking at lighting such as dome lamps, interior lamps, glove box, etc. I'm also looking for wiring that doesn't look factory. Sometimes people wire aftermarket accessories to battery circuits that should be on accessory circuits. I remembered the customer mentioned that his radio had stopped working right before he started having the problem but that no one had thought that was related ( I was not the first place he took his car.) The radio was factory and no extra wiring there but with that radio still in mind, and while checking that the rear trunk light was working properly I took a look at the two rear speakers that hang down into the trunk compartment. One speaker was broken at a porcelain connection point. I'm not a stereo professional but with the porcelain broken one wire was against the speaker frame. I moved the wire away from the metal frame and took another look at the meter.
Major difference! But what was the excessive draw remaining? Well the trunk was still open.
Closed the trunk lid. Looked at the Meter.
Battery draw problem found and traced to right rear speaker. I cut the two wires at the broken connector to prevent the problem re-occuring until (or if) the customer decided to replace the speaker. Like I said, I'm not a stereo specialist but I did see a similar problem with a Mustang caused by a rear amplifier. My guess is this Toyota has an amplifier as well and the speaker caused a problem with the amplifier. Btw, the radio worked fine after, minus one rear speaker.
Do you remember the bad battery? Sometimes you can get life back from an extremely discharged battery if you charge very slowly and up to full capacity. It was worth a try here because the battery was actually new and might just come back despite the test result. I put the charger on the battery and then went back to the car testing.
I needed to test the alternator while I had a good battery on the car. I didn't suspect a bad alternator but it would be stupid to not test it while at this point. You can make an alternator test as simple or as involved as it needs to be. Start with simple. You connect the voltmeter and read your initial battery voltage before starting the car. You start the car and watch that your voltage goes up when the car is running. That is your alternator working. Here I just wanted to see that the alternator was charging. It was.
After an overnight charge on the battery it was back to a 100% charge. I re-installed the battery then did a few engine cranks while headlamps were on to remove the surface charge before re-testing.
Almost finished. I did the previous drain and charging tests with a different battery. To be thorough I need to quick check those things with the re-charged battery that was now once again on the car.
That's the story of the how the magic really works!
Kenneth Hayes
G&G Auto Repair
