How to get rid of voltage problem in Mitsubishi Lancer cedia?

Start by measuring the battery voltage before you start the engine then again with the engine running. Holler back with those numbers.

Both voltages are too low. A fully charged battery will read 12.6 volts. A good but discharged battery will still read 12.0 volts. At 11.5 volts you either have a shorted cell in the battery or it's really really discharged.

The generator must put out between 13.75 and 14.75 volts with the engine running. !3.0 is not enough to force the battery to take a charge. There's two possible causes to look at first. A shorted cell in the battery will tend to hold system voltage down regardless what the generator tries to do. With low system voltage, the voltage is much too low that is causing the current to flow to create the magnetic field inside the generator. When the magnetic field is low, the output developed will also be low.

The second possibility is there's a defective voltage regulator or a defective diode inside the generator. With one bad diode out of the six, you will lose two thirds of the generator's capacity. That will leave it with not enough output current to keep up with demand for the fuel pump and many computers and lights.

The place to start is by using a battery charger to recharge the battery on the lowest setting for a couple of hours, then, with the charger turned off, turn on the headlights for 10 - 15 seconds, turn 'em off, then remeasure the voltage. If it's not near 12.6 volts, replace it.

If the voltage is around 12.6 volts, you should find most of the running symptoms have cleared up during a short test drive. If the voltage continues to drop while driving, suspect the generator or voltage regulator. The voltage regulator is built into the generator on most import vehicles.

Okay, if you do have between 13.75 and 14.75 volts with the engine running, the next thing is to measure that voltage again as you turn on more and more electrical circuits. Start with the head lights, then heater fan and wipers. If the voltage drops significantly each time you turn something on, the generator can't keep up with demand. Only three things can cause that. The belt is loose and slipping, the generator is too small for the vehicle, or it has a bad diode.

Slipping belts are not common anymore with the newer serpentine belts. Unless someone recently replaced the generator, it had a large enough capacity before so the only left that would change that is a bad diode. Your mechanic will find that with a load test. With a professional load tester, it will show how much current can be developed while still maintaining 13.75 volts. The typical generator for your vehicle is a 105 amp unit. Up to three amps goes right back to run the field winding. That leaves around 100 amps which is plenty to run everything on the car. With a bad diode you'll have a hard time getting 35 amps on a load test. The fuel pump takes around 8 amps. Add in the ignition and fuel injection systems, heater fan, and a few lights, and you'll be short and the battery will start to drain to make up the shortfall.

Another clue to a bad diode is very high "ripple". Most professional load testers display ripple on a bar graph, not as a voltage. High ripple is normal from a battery charger. When it is caused by the generator, computers can get confused by the varying voltage and do weird things. If you care to know more about ripple, check out the last section on this page:

http://randysrepairshop.net/charging-systems.html