Battery Light On

TBoneVoodoo

I have bought a new battery every year for three years now. Just got a new Interstate battery a month ago. Leave the car parked for about 3 days and it drags when it starts like its almost dead. After driving it charges and cranks right up normal. If I run the headlights, fog lights, heater, radio, wipers back and front and sit idling about 5 minutes the battery light comes on the dash with a warning sound. I cut off the lights and it goes off for a few more minutes then comes back on. If I cut off everything its fine. All summer its always fine except at night. The battery light comes on after driving a while at stop lights and the heater dies down like the car is going to shut off. New Battery, New Alternator not rebuilt. 97,000 miles on the car 2nd owner. Never changed the radio or anything its all factory. Have hot wired where the door locks and headlights stopped working as others did online just bypassing where the wire went threw and that's all that isn't factory on the car. Thanks for any ideas on how to fix this problem.

Mr_Shiftright

First thing you need to do is check the charging system to determine alternator output. Nothing will work right if the alternator is sub-standard.

If the alternator checks out perfectly, then you'd want to test for a "parasitic drain" on the battery. There are excellent videos on YouTube on how to do this.

TBoneVoodoo

I will check out the videos thanks. I have already had the alternator tested then again after I replaced it for no reason as they were both fine. Something is draining the battery for sure but no one that's looked at it can figure it out so far.

TBoneVoodoo

Okay I did the parasitic test and nothing is showing to be draining the battery at all but the clock memory on the radio and it show 0.05 on the meter. The battery showed a full power of 12 amps so its charged. I watched 5 videos on the parasitic drain before I attempted it to learn all the settings on the meter. Also retested the alternator and its putting out 14 amps. I'm lost to whatever it is that's wrong with it.

Mr_Shiftright

How many milliamps draw?

TBoneVoodoo

50

Mr_Shiftright

Well that's acceptable. I wonder if it would be a good idea to let it sit for a while and do the test again, to see if something is randomly turning on.

TBoneVoodoo

It sat for two day before I tested it. Since the headlights and locks went out over a wire fuse I bypassed I have had this problem mainly when the lights are on at night or when its raining after driving it over 20 mins.

Mr_Shiftright

I wonder if you could do a voltage drop test on both the negative and positive sides of the entire electrical circuit. There might be excessive resistance somewhere.

It would be interesting to see how many amps your alternator is putting out on start up. I guess you'd need some kind of loop meter for that.

TBoneVoodoo

okay i will try that and see. thanks!

Mr_Shiftright

It might be that your battery is drawing too much current from the alternator for some reason. It would also be interesting if you put the battery on a charger overnight and fully topped it up, and then see if the behavior of the car changes in any way.