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battery warning light is on when car is parked

Discussion in '308/328' started by 82 308gtsi, Feb 27, 2007.

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  1. 82 308gtsi

    82 308gtsi Rookie

    May 12, 2004
    9
    #1 82 308gtsi, Feb 27, 2007
    Anyone out there interested in tackling an electrical problem?

    As the title said,my 82 308gtsi battery warning light is on when car is parked and key is at ignition off position or removed from key hole. However, the light goes off when I turn the key to ignition on and will remain off while driving.

    First I suspected, the alternator/regulator is bad, so I measured the battery's voltage changes from park,start engine, and rev.up RPM to confirm my diagnosis. 12V at park, dropped to 10V during start and 14V at 1000 RPM or so. That tell me the alternator/regulator is working just fine.

    Now what's next? There's a short somewhere that causes the light ON, but where?

    Other than this small problem, it's a great daily commute car that give me 21mpg at 70mph after 95000 miles
     
  2. Mike328

    Mike328 F1 Rookie

    Oct 19, 2002
    2,655
    Boulder, CO
    Full Name:
    Mike
    #2 Mike328, Feb 27, 2007
    Something's not right. That light is not supposed to ever come on when the ignition is in the "off" position. Also, that light SHOULD come on when the key is in the "run" position before starting. It should be on after the car has started but before the alternator kicks in (first time 2000 RPM approx is reached). Once the alternator kicks in, it should go out.

    This is a strange problem. You need to find the source of the current to this light when the key is off. You'll need your wiring diagram for this. Are there any mods to the car? Voltmeter, Ammeter, car alarm, etc.?
     
  3. Darolls

    Darolls F1 Veteran
    BANNED

    Jul 2, 2003
    7,782
    Full Name:
    Sparky
    #3 Darolls, Feb 27, 2007
    Check for a blown fuse; you may be getting feedback through a circuit due to it?

    Check ALL fuses.
     
  4. Jbryant

    Jbryant Karting

    Sep 23, 2006
    220
    California City
    Full Name:
    Jeff Bryant
    #4 Jbryant, Feb 27, 2007
    I would like to know how you are getting 21MPG at 70.

    I am only getting 13MPG on a good day.

    Jeff
     
  5. 82 308gtsi

    82 308gtsi Rookie

    May 12, 2004
    9
    #5 82 308gtsi, Feb 28, 2007
    I checked the diagram that's inside the owner manual. 2 wires from the light, one goes to alternator other goes to fues box. That same fuse is used in most instrument lights, oil pressure, exhaust temp warning ..etc and they are functioning normally. The regulator is built inside the alternator, I suspect may be there's a short inside the regulator but somehow not enough to affect regulator function. If so, how do I go about that?

    By the way, I replace timing belt every other year and make sure the timing is set right at the mark. the fuel distributor is adjust almost lean but not lean enough that engine starts knocking. All cylinders have good pressure. That's all I did to get my car running at 21mpg freeway, 17mpg combined
     
  6. Beta Scorpion

    Beta Scorpion Formula 3

    Jun 22, 2006
    1,379
    #6 Beta Scorpion, Feb 28, 2007
    There have been a few posts on this. Probably a result of diodes going bad (internal short) in the alternator.
    Check out Big Tex http://www.ferrarichat.com/forum/showthread.php?t=137807 and my experience

    http://www.ferrarichat.com/forum/sho...1&postcount=25
     
  7. Mike328

    Mike328 F1 Rookie

    Oct 19, 2002
    2,655
    Boulder, CO
    Full Name:
    Mike
    #7 Mike328, Feb 28, 2007

    Agreed, 328 will get 20mpg just freeway cruising.

    On the 328, the wiring is similar, except there are also wires related to the ignition and then the ignition relay (relay "u"). There's also a diode. I think the idea here is that the light can only come on if the ignition is in the "run" position. I do not show any wires going to fuses directly. The wires go to the fuse box area, but I trace them going to relays. They may go through fuses after the relays, though.

    This may relate directly to your issue, since the issue is the light is coming on when ignition switched "off" - a condition I think the relay wiring is designed to prevent. Check that relay, pull the relay with the car off and see what happens. Swap it with a similar one. Also there's a diode - check the diode.

    Another issue: The current for the light has to come from somewhere. From what I can tell by a quick glance at the diagram, it's possible the ignition itself distributes the current to this light, only when in the "on" position and only when there is a voltage differential between what the alternator is putting out and the rest of the system i.e. battery is at 12.5V, alternator is only outputting 10V, light will come on.

    Until the other issues are investigated, I don't believe this is a VR issue in the alternator, not at this point, especially if the light goes off when driving.
     

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