Any car experts?

This is a discussion on Any car experts? within the General Discussions forums, part of the Community Boards category; List of symptoms: 1. Car will not start. The key indicator (the "ding ding" sound when you insert the key) ...

  1. #1
    Captain Crash brewbuck's Avatar
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    Any car experts?

    List of symptoms:

    1. Car will not start. The key indicator (the "ding ding" sound when you insert the key) sounds low pitched, sad, as if the voltage is low.
    2. Measuring the battery with a multimeter shows 12.4 volts, basically a good charge.
    2b. When I first put the leads on, the voltage was 4.5 volts. Then I removed the leads and put them back, and got 12.4 V. WTF?
    3. It is possible to jump start the car, at which point it runs fine until the engine is turned off.
    4. The positive battery terminal connector is very badly corroded (copper is green).

    So my first theory, that the battery is drained, is incorrect, since the voltage is high (and yes, I did sanity-check my multimeter)

    My second theory, that there is a bad terminal connection, is also incorrect, since the car is able to start when jump-started (and a car should not run at all if the battery connection is bad, since the battery is part of the overall circuit).

    My third theory, that there is a problem with the starter motor, is also wrong, since that doesn't explain the weird sounding indicator beep, and the car, as I stated, will start just fine if jump-started.

    I don't know what the hell is going on. The only theory I have left is that the resistance of the corroded terminal connector is through the roof, and I can't draw enough current to turn the starter. But the "ding ding" indicator doesn't require that much current, and yet even that sounds like it's not getting the power it needs. And besides, if the terminal resistance was super high, that terminal should be getting ultra-hot, and that's not happening.

    Any ideas? I'm going to pull the terminal connector off and clean it with a wire brush just to see what happens.
    Code:
    //try
    //{
    	if (a) do { f( b); } while(1);
    	else   do { f(!b); } while(1);
    //}

  2. #2
    and the Hat of Guessing tabstop's Avatar
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    I had 1, 2, 3, and 4 with my car, and cleaning the battery terminals was what was required.

  3. #3
    Guest Sebastiani's Avatar
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    >> Measuring the battery with a multimeter shows 12.4 volts, basically a good charge.

    A 12 volt battery should actually read 13 - 14 volts. Even so, the amps are just as important (should be marked on the battery somewhere).

    You probably just need to replace the terminal and recharge the battery (driving around for 1/2 an hour should do it). The reason why a jump start works is because the energy is going directly to the starting system - no battery involved there. Once running, the alternator keeps everything going, of course, but due to the bad connection the battery never gets recharged.

    Just for good measure, it's a good idea to check the water level in the battery from time to time, as well (some batteries don't have ports for this, though). Be careful though, as sulphuric acid is corrosive and batteries can explode if mishandled (you might get a mechanic to check it for you).
    Code:
    #include <cmath>
    #include <complex>
    bool euler_flip(bool value)
    {
        return std::pow
        (
            std::complex<float>(std::exp(1.0)), 
            std::complex<float>(0, 1) 
            * std::complex<float>(std::atan(1.0)
            *(1 << (value + 2)))
        ).real() < 0;
    }

  4. #4
    Captain Crash brewbuck's Avatar
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    I think you guys are probably right, but what I still don't understand is how the overall circuit of the car can be operating when the connection through the battery is bad. Isn't the battery in series with the overall circuit? For instance, if you pull the ground terminal while a car is running, it dies. Or am I wrong about that?

    Maybe there is just enough current getting through to fire the plugs and run the radio, but if there's enough current for that, why does the key indicator sound so funky?

    I'm sure it's the problem, but I don't "get it" from an electrical standpoint.
    Code:
    //try
    //{
    	if (a) do { f( b); } while(1);
    	else   do { f(!b); } while(1);
    //}

  5. #5
    Guest Sebastiani's Avatar
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    >> Isn't the battery in series with the overall circuit?

    No, it's connected in parallel.

    >> For instance, if you pull the ground terminal while a car is running, it dies. Or am I wrong about that?

    That should only happen if you have a bad alternator.

    >> I had 1, 2, 3, and 4 with my car, and cleaning the battery terminals was what was required.

    You can usually get by with cleaning the cables, but it won't work if the conductor has been compromised by the corrosion, obviously. Worse yet, corrosion can spread up into the wires, and it would be a good idea to cut back the insulation and check for corrosion there, as well. If you do find it there you'll need to replace the wires, of course. Finally, after cleaning the terminal, or as you're replacing it, be sure to apply an anti-corrosive substance to both the battery terminal and connector before reattaching it.
    Code:
    #include <cmath>
    #include <complex>
    bool euler_flip(bool value)
    {
        return std::pow
        (
            std::complex<float>(std::exp(1.0)), 
            std::complex<float>(0, 1) 
            * std::complex<float>(std::atan(1.0)
            *(1 << (value + 2)))
        ).real() < 0;
    }

  6. #6
    Captain Crash brewbuck's Avatar
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    Quote Originally Posted by Sebastiani View Post
    >> Isn't the battery in series with the overall circuit?

    No, it's connected in parallel.
    Well, you've shattered my world-view. If the battery is in parallel, how can the alternator ever charge it? How does it force current through the battery when that current might just as well flow through the other half of the circuit? (I believe you, but once again I don't "get it")

    You can usually get by with cleaning the cables, but it won't work if the conductor has been compromised by the corrosion, obviously. Worse yet, corrosion can spread up into the wires, and it would be a good idea to cut back the insulation and check for corrosion there, as well. If you do find it there you'll need to replace the wires, of course. Finally, after cleaning the terminal, or as you're replacing it, be sure to apply an anti-corrosive substance to both the battery terminal and connector before reattaching it.
    The cables are awful. The positive terminal has a rubber hood covering it, that thing is old and ratty. There seem to be two conductors leading from the positive terminal -- one goes to the alternator, the other goes, presumably, to the rest of the car's circuits. Both of these conductors have sheaths which look like... donkey butt. I'll get them replaced, but for the immediate future I just want the thing to work again.

    Thanks a lot for the input. I was getting ready to buy a new battery.
    Code:
    //try
    //{
    	if (a) do { f( b); } while(1);
    	else   do { f(!b); } while(1);
    //}

  7. #7
    Guest Sebastiani's Avatar
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    >> If the battery is in parallel, how can the alternator ever charge it? How does it force current through the battery when that current might just as well flow through the other half of the circuit?

    Let's say you have X amount of electrons flowing through a wire. You can connect any number of loads in parallel, and they will simply take their share of electrons (Ln/X, say). Of course, if you add too many loads then the available supply is not enough, in which case you'd just need a more powerful generator! And in the case of a battery it draws current from the alternator until it reaches a point of saturation, at which point it stops being a 'load' for some time until it leaks of some current and the cycle continues.

    >> I'm sure it's the problem, but I don't "get it" from an electrical standpoint.

    Probably, but you never can be *too* sure with electrical systems. A lot of things can go wrong there and the symptoms can often be very ambiguous.
    Code:
    #include <cmath>
    #include <complex>
    bool euler_flip(bool value)
    {
        return std::pow
        (
            std::complex<float>(std::exp(1.0)), 
            std::complex<float>(0, 1) 
            * std::complex<float>(std::atan(1.0)
            *(1 << (value + 2)))
        ).real() < 0;
    }

  8. #8
    Super Moderator VirtualAce's Avatar
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    1. Car will not start. The key indicator (the "ding ding" sound when you insert the key) sounds low pitched, sad, as if the voltage is low.
    Car will not crank.
    • Faulty relay in a non-starter circuit causing voltage drops indicated by the odd low pitch of the chime module. Faulty wiring in the circuit and/or faulty connections at the connectors. While at the factory I had no end to faulty connectors due to assemblers incorrectly connecting two ends of a wiring harness together. This can cause shorts, fires, and component failures. It can also allow moisture into the circuit causing all sorts of problems. This happens a lot and is probably one of the biggest reasons for electrically related recalls on equipment and cars.
    • Voltage drops caused by a partial short to ground (unlikely)
    • Bad starter motor (usually is a progressive failure - not normally an instant failure)
    • Bad starter relay (can fault at any time) - indications are cranking with no starter motor action but there is a noticeable 'click'. The 'click' indicates the relay is at least getting voltage but does not necessarily mean the relay is good. Relay's can leak voltage due to faulty internals and can cause very odd circuit behavior. Usually but not always causes flickering dash lights and/or other lights. Can also cause incorrect gas gauge readings and in newer cars with all digital dashes can wreak havoc on just about every gauge
    • Bad battery, one or more bad cells in battery, bad connection at terminals
    • Faulty starter protection circuit. Some cars have key starter protection built into them. If this module is faulty the car will not start - even with a jump. Since yours starts with a jump I doubt this is the issue.


    Car will crank, but will not start
    • Faulty fuel pump. Turn the ignition to on but do not crank and listen for a 'whirring' sound. This is the electronic fuel pump in the tank priming. If it fails to prime, replace the pump. Jump the car and let it run at idle for about 20 to 30 minutes. If the car begins to stutter and/or stall out this indicates a posssible fuel pump issue. It could be that the fuel pump cannot deliver the requested amount of fuel and indicates it needs to be replaced.
    • Faulty/clogged fuel filter. If the fuel filter is clogged the engine will not start. However this is usually a gradual process and you would notice stalling/choking out long before it just would not start.
    • Faulty/clogged injectors. Injectors should 'tick' when delivering fuel. Usually trips the check engine light with a code in the computer.
    • Faulty/fouled plugs. If the fuel pump has been gradually dying and you have had to crank several times to start the car it is possible the plugs have become fouled. Wait for a couple of hours and try again. This will allow the excess fuel on the plugs to evaporate so they can fire correctly.
    • Faulty high energy ignition module and/or coil packs. These can fail at a moments notice. Cannot usually jump the car when these have failed.
    • Faulty/old plug wires. Can cause misfires which also will trip the engine light with a failure code indicating cylinder misfire and will also indicate which cylinder had the problem.
    • Incorrect spark plug gapping. This can cause misfires and hard or no starting.
    • Faulty/clogged catalytic converter.
    • Bad O2 sensors. Computer is getting the wrong information.
    • Bad computer. On modern cars the computer is heavily involved in the starting process. If it is bad the car will not start or may start intermittently.

    Test the circuit with a voltmeter to measure the voltage drops across key areas of the circuit. Ideally the voltage drop across an open relay should be 100%. If voltage is leaking across the relay, replace the relay. Test for short to ground conditions at all key points in the circuit. I doubt it is a short to ground since this normally results in total circuit failure and blown fuses or fusible links. In a normally closed circuit there should be 0% voltage drop from positive to negative/ground. In an open circuit there should be 100% voltage drop from positive to negative/ground. Use a voltmeter to test short to ground using the negative terminal of the battery and placing the positive lead somewhere in the circuit.

    Significant voltage drops across closed components indicate the component needs to be replaced.
    Significant voltage leaks across open components indicate the component needs to be replaced.

    2. Measuring the battery with a multimeter shows 12.4 volts, basically a good charge.
    2b. When I first put the leads on, the voltage was 4.5 volts. Then I removed the leads and put them back, and got 12.4 V. WTF?
    Suspect you got a bad reading on the first go around. This can happen if the terminals are corroded or the leads of your multimeter are not positioned correctly. If the car is off there should be theoretically nothing happening in the starter circuit so there should be no voltage drops. 4.5v indicates a nearly 8v voltage drop somehwere in the circuit. Test the voltage in the starter circuit during cranking. Be extremely careful not to test the high voltage side of the circuit. You only want to test as far as the relay. Do not test where the voltage has been ramped up to turn the starter motor.

    3. It is possible to jump start the car, at which point it runs fine until the engine is turned off.
    This indicates a problem in the starter circuit or at the battery. Check for faulty starter relay - sticking, partial contact, buzzing, etc. Relays should not leak when closed and should not cause significant drops when open. There will be some drop indicated by a digital multi-meter but it will be milli-volts and this is due to resistance inside the relay. 1v+ drops across a closed relay indicate high resistance in the relay and it should be replaced. 1v+ leaks across an open relay indicate faulty contact inside the relay and it should be replaced. To find the starter relay crank the ignition and listen near the passenger side dash for an audible 'click'. There are normally to the right of the middle air vents and just above the glove compartment area. Also not that just because the car runs, but will not start on it's own, does not mean the computer is good.

    4. The positive battery terminal connector is very badly corroded (copper is green).
    Coca-Cola works wonders on these. However you can purchase battery terminal cleaners that will do the trick. You must have a good connection both on the positive and negative/ground sides of the battery. DC will not work correctly if there is a problem at the power source or a short to ground anywhere in the circuit. Check all cables leading to the battery as these sometimes get corroded and cause faulty connections. Replace all cables/connectors that are corroded beyond repair. Check chassis ground connections - sometimes these corrode and rust out.

    That is certainly not an exhaustive list. If a car won't start it's either electrical, fuel, or exhaust related. You must slowly rule out each area to narrow down where the problem is. I would start with the obvious which is the corroded terminals. Usually, but not always, the simplest answer is the correct one. Electrical problems are extremely difficult to find but usually very simple to repair. Right before I became a computer programmer I was about to become an electrical technician at the factory. I'll take computer programming any day.
    Last edited by VirtualAce; 07-21-2009 at 08:16 PM.

  9. #9
    Captain Crash brewbuck's Avatar
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    Well, the problem was the positive terminal. Took it off, cleaned it out with some copper wool, put it back on and she fired right up.

    I realize that my confusion was due to the erroneous thinking that the battery was in series with the alternator (it's not that stupid of an idea if you imagine some diodes and some intelligent circuitry on the charge controller).

    But that's how it goes, right? You get one fundamental idea wrong and the whole world makes no sense.
    Code:
    //try
    //{
    	if (a) do { f( b); } while(1);
    	else   do { f(!b); } while(1);
    //}

  10. #10
    Super Moderator VirtualAce's Avatar
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    Most circuitry in a car or machine is in parallel.

  11. #11
    Guest Sebastiani's Avatar
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    >> But that's how it goes, right? You get one fundamental idea wrong and the whole world makes no sense.

    Well, at least that's a sign of logical thoroughness (which appears to be one your strengths, I might add).
    Code:
    #include <cmath>
    #include <complex>
    bool euler_flip(bool value)
    {
        return std::pow
        (
            std::complex<float>(std::exp(1.0)), 
            std::complex<float>(0, 1) 
            * std::complex<float>(std::atan(1.0)
            *(1 << (value + 2)))
        ).real() < 0;
    }

  12. #12
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    If the terminal voltage drops that much on load, perhaps the battery has an unusually high internal resistance?

  13. #13
    Guest Sebastiani's Avatar
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    >> If the terminal voltage drops that much on load, perhaps the battery has an unusually high internal resistance?

    True, but in this case it might have been just a "bad" reading, which is something you see from time to time with certain meters, and in fact almost any meter with a bad battery will produce strange output. It's usually helpful to have a "known good" system to check the meter with before you start testing, just to be sure.
    Code:
    #include <cmath>
    #include <complex>
    bool euler_flip(bool value)
    {
        return std::pow
        (
            std::complex<float>(std::exp(1.0)), 
            std::complex<float>(0, 1) 
            * std::complex<float>(std::atan(1.0)
            *(1 << (value + 2)))
        ).real() < 0;
    }

  14. #14
    spurious conceit MK27's Avatar
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    Sheesh. A guy with your income should be able to hire someone for this kind of thing

    Next time, try www.RentAMechanic.com
    C programming resources:
    GNU C Function and Macro Index -- glibc reference manual
    The C Book -- nice online learner guide
    Current ISO draft standard
    CCAN -- new CPAN like open source library repository
    3 (different) GNU debugger tutorials: #1 -- #2 -- #3
    cpwiki -- our wiki on sourceforge

  15. #15
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    Quote Originally Posted by brewbuck View Post
    So my first theory, that the battery is drained, is incorrect, since the voltage is high (and yes, I did sanity-check my multimeter)
    Checking battery condition with just a simple voltmeter is not sufficient. You need to check the battery under some prescribed load to see how the voltage holds up. Voltmeters by their nature induce very lillte load of their own, and yet what's expected of a car battery is of course a much greater load.

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