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    battery drain

    My battery keeps draining itself on the 86 es with the m50. I woke up today and it fired right up, i drove it to school, when i tried to drive to go get lunch it wouldn't start. After school, i compression started it and drove it home, shut it off, and restarted it and it fired fine. Now, an hour later, the battery is again dead. Any ideas on whats happening, and where does the battery cable run, under the car or what?


    86 Zinno es
    M50 inside

    #2
    The first thing to do is to determine whether there is excessive parasitic draw by measuring the current draw from the battery with the engine off and all doors and trunk closed. Normal parasitic draw would be 30-60ma. If the parasitic draw is normal, the alternator and battery become the prime suspects.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

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      #3
      Alright im grabbing my buddies multimeter as soon as i can get a ride. If its high do i go through the fuse box one by one until the draw drops?


      86 Zinno es
      M50 inside

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        #4
        I cant measure parasitic draw until tomorrow it turns out, but the battery is making 14 volts at all times, and when i try to crank it the starter solenoid just clicks and the battery volts stay at 14.


        86 Zinno es
        M50 inside

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          #5
          Check the ground strap to the battery jeese. If you have any problems tomorrow give me a call after you get out of school.

          www.gutenparts.com
          One stop shopping for NEW, USED and EURO PARTS!

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            #6
            There is no way that the battery can "make 14 volts". The maximum that a 12v lead-acid battery can produce is 12.7v (fully charged). However, system voltage with the engine running can be between 13.5 and 14.5v
            The car makes it possible, but the driver makes it happen.
            Jim Levie, Huntsville, AL

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              #7
              here's an odd possibility. Does your battery light come on when you turn the key over? my buddy ran into a similar problem to yours and we found out that if the battery light isn't coming on then the battery isn't charging. but since you can drive it when its started without battery issues that may not be your problem

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                #8
                Originally posted by jeffw View Post
                here's an odd possibility. Does your battery light come on when you turn the key over? my buddy ran into a similar problem to yours and we found out that if the battery light isn't coming on then the battery isn't charging. but since you can drive it when its started without battery issues that may not be your problem
                i think upto 86 or 87 they didn't have the resistor if the bulb burnt out. Either way, I've seen the alternator kick on at 3k without the exciter circuit. It's something to check for sure.
                '84 318i M10B18 147- Safari Beige
                NA: 93whp/90ftlbs, MS2E w/ LC, 2-Step
                Turbo: 221whp/214ftlbs, MS3x flex @ 17psi

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                  #9
                  Sorry i dont know shit about electrical. I put the multimeter on the battery posts and it read 14.2 volts. But im pretty sure its just the starter


                  86 Zinno es
                  M50 inside

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