Car electrical drain challenge

Factual Questions
1

I’ve got a '88 Dodge Shadow that I purchased from an elderly neighbor back when gas was selling for $4+ a gallon. It looks fine, runs excellent and seems to get 30+ MPG when driven with fuel economy in mind. Though it hasn’t been driven lately now that gas is at a more agreeable price, I am wanting to keep it road worthy in case another hurricane that knocks out some refineries give the gas companies the justification to price gouge again.

I have been well served by this tiny car (that’s called “Stinky” by my wife due to a missing can of crabmeat from a grocery bag that was discovered under the passenger seat, after it exploded during the summer).

I experienced a dead battery a couple days ago, replaced it only to have the new battery drain seemingly overnight.

Here’s some facts that might help shed light on the culprit:

[ul]
[li]The voltage of the alternator reads at 15-16 volts[/li][li]The engine seemed to be getting full power from the battery for about 1/2 a second when starting before outright dying (no dash lights, dome lights, etc)[/li][li]With a fresh battery or jumper box, the car starts right up[/li][li]One of the times the car was jumped, a large spark jumped from the positive terminal, not upon connecting but when the key in the ignition was turned[/li][/ul]

I suspect the following things items might be responsible, with likelihood roughly in this order:
[ol]
[li]Aftermarket stereo that I installed last year is somehow shorting out and causing an electrical drain while the car is off (especially considering how I messed with the wiring the day before these symptoms began[/li][li]Diode in alternator that ensures unilateral energy flow is “leaky”, causing a electrical drain by turning alternator into a motor while engine is off [/li][li]An intermittent short somewhere in ignition system[/li][/ol]

My planned course of action:

[ul]
[li]Recharge battery [/li][li]Disconnect power to aftermarket stereo[/li][li]Inspect all wiring (to starter, alternator, etc)][/li][li]Reconnect battery[/li][li]Have a jumper on hand just in case battery tanks again and at this point look into purchasing an ammeter and start pulling fuses.[/li][li]Start looking into purchasing a reman alternator from Advanced Auto or the like.[/li][/ul]

Considering the spark during ignition, the draining of the battery while parked overnight and the fact the car suddenly started draining batteries soon after I monkeyed with the stereo, does the above sound logical? Having already purchased an $85 battery that I probably didn’t need, I don’t want to purchase an alternator until it become obvious that is indeed the problem.

Does anyone have other ideas what the culprit might be that I can look into as well?

Thanks in advance for your help!

2
  1. Put an meter in series with the positive terminal of the battery, and measure the current when the car is off. Start pulling fuses to see if you can isolate which branch is causing the problem.
  2. The “large spark” coming from the positive terminal when the car was started tells me that you have crappy terminal connectors and wires. Cut the old clamps off, and get nice new ones from your local auto parts store. Clean up the cable ends and install. Doing this can make all the difference in the world.
3

That’s too high, possibly overheating the battery and causing electrolyte loss. It shouldn’t be more than 14,6 volts tops.

4

Assuming he’s looking at the gauge on the dashboard, that’s not unreasonable.

The part about it appearing to get full power for a second or two, combined with the big spark, sounds like a classic case of corroded cables to me. To the OP, how long did it take the battery to recharge on the charger?

5

Start by checking your grounding wires.

6

If there are sparks coming from the positive terminal on the battery when you try to start the car, you have a bad connection to the positive terminal. Remove the clamp from the positive terminal and make sure the inside of the clamp is clean and free of corrosion. They make a round wirebrush you can stick in there and clean the inside of the clamp (the other side of the brush is usually female and can be used to clean the outside of the terminal post on the battery). Then put the clamp back on and make sure it’s good and tight.

7

as others have the spark at the terminal indicates a dirty terminal with high resistance.

the high resistance wil cause a voltage drop when the car is started and after the car is started make it dificult to recharge the battery. And can cause the alternator voltage to be high.

8

Do you own a digital volt meter, and or a 12V test light?