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Battery dies only when I try to start the car

I've got a 2001 Nissan Sentra driving me crazy. The problem is that when I turn the key to the "start" position, I hear a click and all the electrical dies. When I jump it, the car starts fine.



This is where it gets strange. I can come back to my car and the electrical works fine. I can play the radio, honk the horn, crank the A/C with no problem. As soon as I turn the switch to the start position to start the engine everything dies again. I tried cleaning the terminals and once again I had power... until I tried to start it. Again, "click" and my electrical stops working.



I had the battery and alternator checked - both were fine. Even after all of the electrical dies on me, the battery itself still has a charge. Removing the lead from the terminal and reattaching it makes everything work again until I try to start it.



Any ideas?
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Comments

  • edited August 2009
    You're describing the classic symptoms of a near-dead battery. Lights, radio, horn, AC fan, etc, only need 12 volts to work, which the battery still has, so they still work.

    Starting the engine takes AMPERAGE, which your battery no longer has enough of. Ask someone to "load test" the battery. If it passes I'll be amazed.

    If this is the original battery it's just one more indication that it's time for a new one.
  • edited August 2009
    In order for the starter motor to work like it is supposed to it requires more current from the battery than any other electrical device on the car. This puts a big load on the battery. The problem you describe is due to either a battery with a low charge, faulty wiring to the starter or, the starter motor itself is bad. Have the motor checked to see if it is drawing too much current from the battery.
  • edited August 2009

    Please allow me to echo what mcparadise stated. All of the accessories that you mentioned consume FAR less amperage than the starter motor. Trust me--most batteries that are incapable of turning the starter motor will allow lights, horn, etc to function.

    As was said, if this is the original battery, it is OVERDUE for replacement. In fact, by using the original battery for too long, it is possible to damage your expensive alternator.
  • edited August 2009
    Thanks for the reply. That was my thought too. I had it load tested and it passed. The battery itself is only about two years old. I'll have the wiring and starter checked.
  • edited August 2009
    Thank you for your help. Your "faulty wiring" idea led me to examine the actual wire connected to the terminal. It looks like part of the starter wire is exposed and corroded just a little bit past the lead connecting to the terminal. Do you think that could be causing the problem?
  • edited August 2009
    You need to remove the clamps from the battery posts and SCRAPE both surfaces (posts and clamps) down to bare metal. The surfaces can look clean but still have a layer of lead oxide providing a bad electrical connection. Make sure the other ends of the battery cables also have a corrosion free connection.
  • edited August 2009
    I'm thinking along the same line as Gary123: The symptoms indicate a poor connection between a battery terminal and the clamp on that terminal (maybe both terminals/clamps). When you try the starter, the current causes a big voltage drop across the poor connection -- the voltage on the wires would drop way down, even if the battery were OK.

    An easy way to test it (to make sure you have to pull the clamps and clean everything up): while trying the starter, measure the voltage at the battery terminal posts. That is, on the posts themselves, not on the clamps or any other part of the wiring. (Note that with "modern" batteries that have screw-in connections rather than clamps, this test cannot be done.) If the battery voltage stays up where it should be (about 12-point-something volts), then you have a poor connection. You could even measure the voltage between each battery post and its clamp to try to see which connection needs fixed.

    And, yes, the corrosion on the starter cable MIGHT BE related to the voltage drop problem. Corrosion there could imply corrosion on the terminal/clamp mating surfaces. But corrosion on the cable indicates another risk: it could mean that the wire is corroding through. If the wire does corrode through -- or even only most of the way through, for the starter cable -- you will lose battery power. Check the wire, and (if needed) fix it before it breaks.
  • edited August 2009
    Yea, a poor connection anywhere in the chain can be such a problem. Remember to disconnect and clean both ends of each suspect wire. Sometimes a wire or connection look great, but have a problem under the insulation of connection point.
  • edited August 2009
    Internal corrosion of the main wire to the starter can cause this kind of trouble. If you have a jumper cable you can use it to bypass the wire to see if that clears the trouble. If the starter works ok doing that then install a new cable. Internal wire corrosion is a fairly common problem.
  • edited August 2009
    If you have a voltmeter, you can pinpoint the problem. Put the leads of the meter directly on the battery posts ( not the clamps ). Try starting the car. Normally, the voltage will drop to about 10 volts because of the load. If it drops much more than that, the battery is bad.

    If the battery appears OK, move the leads one at a time to the clamps, the engine block, etc. until you get a big drop in voltage when starting.

    I assume that when jump-starting the car, you connect the negative jumper cable to the engine block (proper procedure). Doing this bypasses the existing negative battery cable which is probably your problem.
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