It's been a while since I last posted something here. I need your help in figuring out what is draining my battery. It started 2 days ago. I have had my battery charged and tested. It came back good after the first day. Then I took my car in with the car running and had them run an alt test which came back steady though a bit low.

Yesterday (so day 2) I took my multimeter out and tested the battery voltage at 13.4V (with car off) and with the car running at 13.9 V.

So from all indicators, I have a good battery and alternator. Yet overnight (for the 2nd night in a row) the battery is completely drained (no lights come on, power door locks won't work, etc). I did not have time to check my battery voltage but after the first night it was down to 8.7 V. I assume something similar after the 2nd night.

I will get the battery charged up and will disconnect it overnight to verify that it is not the battery.

Any help in figuring out what the battery draw is would be much appreciated. Anyone have anything that you were able to fix?

I only have 1 aftermarket accessory, a CD player but I haven't used that in a long time. It is not disconnected but maybe that is the first thing I need to do. Any other thoughts? I have turned off the dome light and the headlights were all off on both nights.

Thank you for helping me get to the bottom of this one.

 

Check the trunk light. Open the trunk and immediately feel if the light is already warm from staying on. (This assumes of course that the car has been sitting with a live battery connected for a while).

Disconnecting the battery while parked is the critical test.

13.4 with the battery at rest is kind of a lot. It is usually in the 12's. Cheap digital voltmeters will read HIGHER than the actual voltage if the 9 volt battery in the meter is weak. If you don't have 13.8 volts with the engine running but everything else turned off, the alternator isn't working very well.

 

Thanks. I have not had the guts to leave it on for a long time after having to recharge the battery twice. Would the trunk light feel warm even after 1 hr? I can try that. I checked the trunk light while everything was closed from the back seat and did not see it lit up.

I did connect my multimeter and noticed that it is drawing 3.2 amps of current while the battery is connected. I removed my aftermarket CD player and it did not change the current draw which conclusively removes that as the source. Any help would be greatly appreciate. 3.2 amps is a lot in my eyes.

 

Did this aftermarket CD player involve an external amplifier? Those are a common cause of battery drain. Look under the seats and in the trunk. If there are any aftermarket wires connected direct to the battery, disconnect them.

3.2A is a lot of current. Does the key actually turn off everything that should be off when the key is off (turn signals, wipers, heater, etc)? You could leave the ammeter connected and start pulling fuses to try to see what stops it.

 

I just might have to resort to pulling fuses at this point. Something big is draining this battery. My aftermarket CD player is only the player. No amps of any kind. I'll try to get to the bottom of this and let you all know soon. I hope that this is not a ground wire problem as they can be difficult to spot and fix.

 

An update is in order. I have done 2 sets of things.
First, I pulled every fuse out of the car both the ones under the steering wheel and the ones under the hood on the passenger side. My car does not have any ABS. Even after pulling all the fuses out, the car was draining at 2.8 amps. Thinking that this means it was a bad battery, (2) I changed the battery out since it was still under warranty.

Unfortunately steps 1 and 2 did not solve the problem. 2 days later, my battery was too low to start the car today.

I'm back to square one. If pulling the fuses did not yield a solution, does this mean that I have a short somewhere from the batttery to the starter to the alternator? If so, how can I tell? If I unplug the wires to the alternator will that disconnect everything and therefore not tell me the problem is with the alternator or will that yield information for me.

As I was measuring current it seems to be fluctuating quite a bit. It started at 2.5 amps and then went down to 10 mA and then went back up all within a 5 min time span.

Any help would be greatly appreciate.

 

Disconnect the big white wire at the alternator. If that stops the drain, replace alternator. Do not run the engine with the wire disconnected.

 

mk, have you seen this youtube video?

My system is doing this exact same thing. My first battery had a consistent current of 3.24 amps when everything was off. So I got a different battery. This one has a 2.5 amp current draw for a few seconds and then drops down to about 10 mA. So I know that the current draw is normal but my battery still died overnight. So I tried this test following the youtube video and my voltmeter does exactly the same thing. As soon as I connect the alternator with no keys etc, the voltage begins to drop steadily but without the alternator plugged in, it remains steady.

I'm suspecting that it is the alternator and will replace it tomorrow but I wanted to get your opinion on this test on youtube. It happens to be on a 99 civic which is the same gen as mine. Thank you for all your help so far.

 

The 4 wires in the round plug, unplugged from the alternator, should not have voltage to ground with the key off. If there is voltage there it's a problem with the car wiring not the alternator.

 

Thanks, mk. I went ahead and replaced the alternator. I hope this fixes the issue. I'll try it over the next two nights. If not, I'll take a look at the wires to see if they are causing a short.

One slight difference so far is that the battery light comes on when I turn the key. It was not coming on while I was having the battery drain. Hopefully that is a good sign that it was indeed the alternator itself and not the wiring.