My car battery stops working-sort of. Here is what happened recently:

- I replaced the radiator and a few things connected to it. I discovered that the fuse for the cooling fan is missing(I don't know if one was there since I got the car) . So I put one in (20A). When I turn the ac on, the cooling fan and condenser fan would come on at the same time for about 30s then stop, and repeat after 15s or so, I don't know if this is normal.

- The battery die after I didn't use my car for a week. I have to jump start. I was able to start my car if I drove it everyday (usually about 30 minutes), but the battery is weak. If I don't drive it for about 2 days, the battery dies again.

So I check the voltage.

- The voltage show 12.4v_ when the engine is not running.
- I have to jump start- it show 14.3v when the engine is running and nothing is on ( light, ac, radio...)
- When running, rev at 1500 rpm, and everything is on(light,ac, radio...), the voltage drop to 11._v ->10._v ->9._v and lower, but jump up about one number when the fans (cooling and condenser) stop , and continue to drop when the fans turn on. If either the ac or the headlights is off, the voltage will jump up and stay around 13.5v.
- So I removed the fuse of the cooling fan (mention above), and turn everything on(ac, lights...) when the engine is running-1500rpm. No more voltage drop. And the condenser fan is running- NONSTOP ( maybe because the engine was running about 20 minutes before removing the fuse of the cooling fan or the ac is on- I have no experience). So I turn off everything one by one: voltage is 12.8v when highbeams off, 13.9v when headlights off, 14.05v when ac off , 14.18v when fan inside car's off and the same when radio's off.

- I did the alternator test as this video shows and everything is good --I can't do a battery test yet b/c the car won't start after I turn it off(bad decision ), need to wait for someone to get home to do jump start and drive it around to charge the battery.

Base on my long story, I would like to see if anyone can give suggestions

Thanks

 

I'm leaning towards a bad battery.

But maybe something in the car is draining it? Test by driving around to charge the battery. Stop the car & disconnect the negative cable from the battery post. After 2 days hook up the battery & see if the battery is drained. If it drains while disconnected, then the battery is bad.

 

I jumped start to go to school this morning.It died in the parking lot. To put my self out of misery, I went to oreilly and get a new battery. They also have a tool to test my old battery, and said it is bad.

- Just a little question. I test draining on the new battery and it is 0.1A. Is this normal?(I found the fuse drawing the Amp: backup ACC, but will post a new thread if I can't find a fix)

Thanks in advance

 

Not sure but 100 milliamps sound a bit high. How did you measure that?

If you simply have the key in the ignition (switched off) there's some loads that can still be active. You might have to figure out how to make the alarm system think the hood is closed, then wait a few minutes for things like the multiplexer modules to shut down.

A couple of watts might be something silly like a lamp inside the glovebox that times out & turns off after 2 minutes. Or maybe something is preventing it from shutting off and it stays on forever...

 

I closed everything (door, lights.. and no key in there), popoff the hood, remove the negative cable, connect the cable to one end of the multi-meter, the other end(multimeter) connect to the battery. I think maybe the alarm as you said. I'll try to search a way to work with it. Thanks

 

It may be as simple as doing just the same thing but continuing to measure for a few minutes. Computers & things will "wake up" when you re-connect the battery through the multi-meter. You might find the current measurement will drop lower after a few minutes.

 

I let the car sit for 2 days. then recheck it. It shows zero drawing now . Thanks a lot