Battery good, alternator good, when vehicle sits for a period something drains the battery. if disconnect battery cable and leave sit can reconnect days later and it will start no problem. Any idea of where there may be a short in the electrical system that would cause this?

have the battery load tested first
then have the alternator and voltage regulator check for correct operation by an accredited auto electrician

if this is a what I refer to as newer model vehicles 93 to 95 and up if you disconnect the battery cable while it is running it kills power to the computer and the car will shut down, it can also fry the computer. That is something that you could do a really long time ago, but now can cause expensive damage. I would suggest taking car to Auto Zone or Advance. let them check the battery and alternator even though they are new.. I cant tell you how many new alternators fresh out of the box I have installed and were defective. same can go for batteries they sometimes can sit on a shelf 6 months before being sold and can start to break down and they will not hold a charge. if they both test ok. you need to check for a parasitic drain. I believe Auto Zone will do that for you for free like the battery and alternator test. if not take a multi meter,,put leads on battery and see if voltage is slowly dropping over a period of an hour or two. then you can start removing fuses one by one and see if voltage drop stops.. if say radio fuse stops it,, you know there is a short or problem with the radio,,

get a12 volt test light (autozone or any part store) . disconnect negative battery. connect light between negative terrminal of batteryand negitive cable if light lights something is useing battery power remove bulbs lighting hood and trunk until test light does not light disconect anything electrical until the test light goes out. if you disconnect alternater and it goes out replace alternator. if this was helpful please leave good feed back

You may have a key off drain. That is where a component, light etc.., stays on or there is a short to ground in the electrical system that drains the battery as it sits. To test this after driving the car disconnect the batterys negative cable, breaks the circuit not allowing a drain, and reconnect it right before driving it again. If it starts right up chances are you do have a drain. If you still have problems then the fault probably lies in the starting/chrging system, battery, starter, or alternator. In any case you should have your car looked at by a shop that does auto electrical work or a versed mechanic that can test the starting/charging system.

Pull the battery take it to any of the chain auto parts stores and have it tested, I bet the battery is no good.

If the vehicle sit for a period of time, even over night and it won't start with the new battery and alternator, you have a dead short drawing voltage from the battery until it goes dead. Disconnect the positive terminal from the battery and connect a test light to the cable and touch the battery positive post with the other end of the tester. If the tester lights up, you have a draw on the battery causing it to go dead. Now you need to pull 1 fuse at a time while the tester is connected to see when the light goes out. When it dies, that is the circuit that needs to be traced to find the faulty switch, bard wire or whatever is the cause. Good luck.

Start with the basics; Is the reason the car does not start is that the battery is discharged after a week of sitting or a case that it won't start without a jump although the battery is still good. If the car just does not start after sitting then try the following; Pull the negative battery cable and let the car sit overnight. Reconnect the cable in the morning and see if it starts. If it does then you are looking for something that is pulling current from the battery. Could be lots of things; light on in the glove box or trunk, a short in a wire, etc. You can try pulling a couple of fuses each evening and in the morning, replace the fuses and see if the car will start after sitting. If it continues to discharge the battery then try another set of fuses. The day it starts after sitting then you have narrowed the electrical system that is discharging your battery. Focus on those systems

It sounds like the battery has a dead cell in it. Replace the battery. If you have an alarm installed remove the in line fuse from the alarm and see if that stops the battery drain.

Batteries will lose power if they sit for long periods of time. It is a good idea to start the vehicle once in awhile to restore the charge to the battery. Batteries will lose their charge and it is not a good idea to let them sit for a long period of time, especially in the winter months. If your battery is older, it may not be holding a charge as good as a new one would.

No, corrosion will not cause a battery to drain, even if the corrosion is on the terminals. Several factors can cause battery drain, I would first have the battery tested to see if the battery it self is not bad. If the battery is good, then the most common is a short. All most all new cars have a certain amount of drain,(measured in milivolts) this drain is for clocks and computer memory's, and it would take several days of a vehicle sitting for the battery to be drained. Don't immediately assume you have a problem if you see 2-6 milivolts of drain on a battery with the key out, now if your battery is being drained after being parked over night, you have a problem. The easiest way to pin down the problem short is to disconnect your positive battery cable from the battery, take a 12 volt test light and clamp one end to the positive cable, and hold the probe to the positive post. Now if you have a short the light will come on. Have someone help you by pulling the fuses one at a time. If when a fuse is pulled the light goes out you have isolated the short to that system. If you pulled all the fuses and the light never went out try disconnecting all the wires from the alternator, 9 times outta 10 do this will let you know where your short is. If the system is not critical like power locks some people just leave the fuse out.