The battery is always running down and there is a power drain somewhere in the system when the car is turned off. I need to check the fuse box manual to know by removing one fuse at a time to see which part of the electrical system is causing the drain on the battery. I don't have the owners manual to check which fuse is for which area of the system
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Re: power drain on battery
Get a fuse tester, which looks like an icepick with a wire coming out the back. Clamp the wire to something metal to make a ground and touch the tops of the fuses which should have small metal prongs on the tops. If the handle of the tester lights up then the fuse is good and if it doesn't then the fuse is bad. Try this out and let me know.
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Could be a fusible link. Depending on the circumstances for a low battery there is a "battery drain sensor somewhere" that is made as a "power saver". It is suppose to keep the battery from being drained and disconnects the culprit automatically. It has been known to even kill the charging system at highway speeds. The driver does not notice the gauge showing discharge and drives until there is not enough juice to run the car.
Something is being left on to drain a battery that quickly, or the system has a dead short in it somewhere. The only drain should come from the alarm system and chronometer in the radio to keep the time correct. That will only drain a battery in about 6 months of not being charged from engine running. I've found the easiest way to check if anything else is still draining power is at the fuse box. With switch off, test each fuse to see if there is still power on them. Then pull the fuse that is still powered and see what isn't working now and the grounded system will show itself. Just leave that fuse out overnight and see does the battery drain down. if not, go thru that system and find the short or faulty unit it's connected to. I always go directly to the grounds to fix problems if something isn't working, yet with your situation, the ground is causing the problem the other way. Something is still connected that shouldn't be.
Jump starting a Lexus (I have one too) only gives enough power to start the car and a modest run will top up the battery. What you need to do is buy a battery charger and FULLY charge the battery. If the battery goes flat after this, there can only be three things wrong.
1.The battery needs replacing due to age or a defective cell.
2. you have a voltage drain somewhere.
3. The alternator isn't charging the battery. Is the charge light on?
I replaced the original OEM battery on my 2005 ES330 about 3 years ago.
I suspect parasitic draw. All vehicles draw some power from the batteries when the car is shut off. Certain accessories such as clocks, radios remote door openers and alarms always need power. The normal power used is called parasitic draw.
It is always a very low draw so it doesn't run the battery down. If you install accessories like shortwave radios or plug things like inverters and portable refrigerators into the accessory socket and operate them too long without the engine running you can drain your batteries to the point where the engine won't start. If there is an electrical short in the vehicle or a malfunctioning accessory it could be drawing much more than its normal load causing a drain on the batteries. If you leave your door open and the inside lights stay on all night you could drain the battery down till the car won't start.
You do not say what brand and model vehicle you have.
The rear window demisters drain a lot of power and are usually programmed to switch off automatically after about 15 or 20 minutes of use. They should also cut out fully when the vehicle's ignition is turned off and of course when you manually switch them off.
1. When you are driving and running a host of electrical units simultaneously in winter there is maximum power drainage and any shortfall in power from the alternator has to be drawn from the battery. This will be a problem if you have a weak battery that is not holding it's charge well or if the battery is not fully charged once it has been nearly or fully drained. It will also be a problem if the alternator is not producing it's optimum power while the vehicle is running.
Batteries do not respond well to being drained frequently and when they are they should always be fully charged again each time with a battery charger at the earliest opportunity. (Running them down and then expecting the vehicle's alternator to do all the battery recharging is not a sound practice).
2. It is possible the rear demister is not shutting down automatically after a period of operation as it is likely to be programmed to do in your vehicle. This is easily checked. If it is not shutting down, and the battery is needed to supplement the vehicles power supply when driving, then the battery can be run down in time.
3. If the rear demister is left active but not shutting down when your ignition is turned off your battery will quickly drain. You should check that power to the rear demister is off once the ignition is switched off (and when you switch the demister off manually). This is unlikely to be a problem but in the unlikely event that you find it is still operating then you can pull the fuse dedicated to the rear demister.
If something is draining the battery you have a parasitic draw on the electrical system . There are a couple ways of testing for this . GM insturment clusters can cause this problem as well as a module not powering down . Really don't think electrical wire burnt problem . The car would catch fire an burn up. The BEST Way TO Perform Parasitic Draw Test
Have the alternator tested, perhaps the battery as well. Otherwise, there may be an electrical drain somewhere and that would have to be looked at by someone who knows about vehicle electrical systems. Try the battery and alternator first....
Having the fan run on for a bit after the engine has stopped is not abnormal in itself, but 20 minutes sounds excessive.
If the fan does eventually shut off, I'd consider changing the thermoswitch (this is a sensor screwed into the radiator somewhere near the bottom, with a pair of wires connected to it - to change it, you'll need to drain the cooling system).
If the fan stays on continuously until the battery is completely flat, see what happens when you unplug the wires from the thermoswitch. If this stops the fan, you need to replace the thermoswitch. If it doesn't, then you need to examine the wiring associated with the switch and the fan, looking for damaged insulation.
You have an electrical short somewhere in the car, and it's what is draining the battery. Put a lightbulb inline with the battery (between the battery and the negative cable). You should see it light up. Get your fusebox diagram out and remove the fuse for the radio and any security system (since power always runs through these). Then remove each fuse one by one, and watch the bulb. When you pull a fuse, if the bulb stays lit, that's not the one you want. Put it back and pull the next one. When you pull a fuse and the bulb goes out, you've found the circuit that is conducting and causing your battery drain. From there, you have to troubleshoot the circuit to find out which component is failing.