What causes a 1998 Mitsubishi Mirage to drain all the energy from the battery in two days even when the alternator is working properly?

Answer 1

AnswerHave your battery load tested. If you are like me, you should be able to leave your headlights on at work all day and still be able to fire the engine up. AnswerDead cell in the battery or something is on. Dome, trunk, hood, or glove box light. Alternator wire malfunctionIt might be the main alternator wire AnswerCheck your charging voltage when the engine is running. Should be about 13.5 - 14.0 volts. Measure across the battery terminals.

You might have a defective electronic device (radio, computer, etc) drawing current when the car is turned off. Using an ammeter and with the ignition turned to off, remove each fuse one by one, and check the current through that circuit by placing the leads of the ammeter across the contacts where the fuse was. Normal readings will be zero, or just a few milliamps. (Start with your ammeter on its highest range - i.e. 10 or 20 amps) A reading more than say 50 milliamps might indicate that there is too much current flowing through that circuit. After checking a circuit, replace the fuse and go to the next one. The radio, computer, and alarm system will probably always have a small amount of current running through them. The computer and the radio have memory and a clock that require power all the time. When you find the circuit that has a large current draw, remove each device on that circuit one by one while measuring the current again, until you find the defective device. The defective device may also be warm to the touch because of the current flowing through it. I have a defective radio in one of my cars that draws 2 amps of power when the car is turned off, and it quickly drains the battery.

Some cars require a special procedure for disconnecting power from their radio, computer, or alarm system. Read your manual before disconnecting the battery. Some car stereo systems require a PIN number be entered after reconnecting power. Some cars require a special procedure to recalibrate the computer because information stored in memory is lost when power is removed. Some transmissions on newer cars need to calibrate theirself for smooth shifting after power has been reconnected. An alarm system will often lose information about the remotes that are used with it.

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