The battery keeps getting drained and dying out

ANSWER : Hello. It is possible that the your 2003 Lexus SC430’s computer is draining the battery during the time that it is not being driven. It is never a good idea to let a car sit for extended periods of time without the engine being run or driven.

If this problem only happens after the car has been sitting for a week or so, this may be caused by something else. Running the engine or driving the car may solve the problem. If it does not, it is also possible that there is a problem with the electric/charging system of your car. If the alternator is faulty and overcharging the battery, it may cause the battery to lose its charge faster than it should. Have a certified technician, like one from YourMechanic, come and complete an inspection of the electric system in order to properly diagnose your problem and make the necessary repair.

ANSWER : This may be a sign of a failing voltage regulator or potentially a bad grounding problem causing a draw on the system. The voltage regulator is a unit that regulates the charging of the battery by the alternator. Often times this will result in the alternator allowing too much power to be delivered to the battery resulting in damaging wires and prematurely sometimes destroying the battery. In other cases it may result in the alternator not supplying enough power to the battery, resulting in undercharging the battery or not charging it at all. In either case, I would recommend having an expert from YourMechanic come to your location to diagnose your vehicle’s charging system.

ANSWER : Hi there. It’s quite possible that you have one of two things causing the drain to the battery. First, you have a bad ground somewhere in the main relay or fuse box or an exposed wire somewhere that is not allowing the circuit to complete from the alternator to the battery. This can cause a battery draining issue as you’re describing, but it could also be one of multiple other electrical problems. The best way to pinpoint the exact source is to have a professional mobile mechanic come to your location and complete a battery will not hold a charge inspection.

ANSWER : Hello, the best thing to do in your case is to install a battery shut off switch. However, you are indicating that your battery is perhaps not accessible enough for such a retrofit. And, of course, if you disconnect the battery you lose anti-theft (alarm) protection as well as the possibility of losing stored info in the PCM.

Generally, the issue with charging in situ is if the charger has a voltage excursion (above 14 volts) which, if it occurred, could damage the PCM and vehicle electronics. Just to be on the safe side, Jaguar simply just says to disconnect the battery. If you are using a high quality professional charger, you are probably safe in leaving the battery connected while charging.

The charging circuit is running through the battery and the likelihood of runaway voltage if you are using a decent charger is low. Note that, even if you use a shut off, lead acid batteries will self discharge anyway, so you will still have to charge the battery every several weeks if you are not using the car. Watch out for gas in the tank oxidizing. Keep the tank full and use fuel stabilizer applied to fresh gas. If the gas goes bad and plugs injectors, you will wish you had "only" a dead battery. If you are continuing to have problems with your battery, a qualified professional from YourMechanic can diagnose the charging issue so that you will not have to keep charging it.

ANSWER : There are three possibilities, to start with: 1) there is a voltage drop in the wiring between the alternator and the battery; 2) the "parasitic" power draw occurs while the car is running, not so much while it is off, thus overwhelming the alternator and consequently the battery is not being fully re-charged; 3) there is a parasitic power draw when the car is off but to pick it up requires data logging. With regard to these possibilities, if you desire that the required diagnostic steps be performed by a certified mechanic, please simply request an electrical circuit/charging system diagnostic. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

ANSWER : Hi, thanks for writing in. This may be a sign of a failing starter relay. The starter relay is a small unit near the starter that directs power to the starter from the battery. When this fails, it may cause a clicking sound and will not allow the starter to engage the flywheel when you turn the key. I would suggest having a professional from YourMechanic come to your home to diagnose your starting issue to determine the solution to get you back on the road.

ANSWER : Hello. If the battery and alternator are fine then I would test the ignition switch. It will commonly stay on and cause this. If it is fine, then an amperage draw test needs to be done on the vehicle. If all of the electronics are stock, then the issue may be a sticking relay. I have had the main fuse box fail internally and cause this a few times on this vehicle and the amperage draw test will identify this as the issue. If you need to have this looked at, consider YourMechanic, as a certified mechanic can come to your home or office to diagnose your battery.

ANSWER : Batteries that drain overnight are common. Usually when this occurs, there is a parasitic drain on one of the car’s systems. When this occurs it drains the battery down over time. Batteries that are drained down repeatedly can cause them to fail. The most common causes of the battery drain are aftermarket accessories, radio, power windows and seat motors. If you can find the cause of the parasitic drain, a certified mobile technician from YourMechanic can come to your car’s location to diagnose your battery and determine what should be done.