ttodhunter Posted August 18, 2011 Share Posted August 18, 2011 This is a new one for me. I had a cheap, but new battery in my Z while I was working on fuel issues. Once my new tank was in and new fuel pump installed, I turned the key to see if I could get fuel pressure- Dead battery. I put a charger on it and the charger just read "not connected properly". Weird, red to red, black to black; what gives? Pulled out the multi meter and it doesn't even know it's touching a battery. Took back to O'Reilly's to have it tested and it doesn't register on their tester. So, I upgraded to the premium battery, put it in the car, and the water main to my house blew so I was distracted for a week or two. Finally get back to the Z and the battery is dead. Hooked it up to the charger and hear clicking over by the intake manifold. It, again, won't take a charge and won't read on the multi meter. I had not made any changes to anything in the engine compartment and it was fine for months until the first dead battery came out of nowhere. Does anyone have any experience with their Z killing batteries to death? Please Help! TIA Quote Link to comment Share on other sites More sharing options...
lester Posted August 18, 2011 Share Posted August 18, 2011 Do you have a cd player in your z? Mine used to run fine and never had a problem with the battery dying. We installed a nice cd player, and now i let it sit for like 3 days and the battery is dead. I already killed two duralast batteries. Good thing they were under warrenty so i just keep going back and getting new ones for free :)Were going to add a cut off switch to the battery soon. Quote Link to comment Share on other sites More sharing options...
ktm Posted August 18, 2011 Share Posted August 18, 2011 I would get a new battery, since you have to anyway, and then do a draw test on the car. Disconnect the negative cable from the battery and place a digital multi-meter between the battery negative post and the ground. Your amperage should measure under 35 mA or so. If it is more, then you have a drain some place. Keeping the DMM in place, start to pull fuses until the drain drops or disappears altogether. You've then found the circuit causing the issue. http://www.popularmechanics.com/cars/how-to/repair/how-to-stop-car-battery-drains Quote Link to comment Share on other sites More sharing options...
ttodhunter Posted August 18, 2011 Author Share Posted August 18, 2011 (edited) Still have the stock radio in there. KTM, that sounds like some good info. I'm pretty dumb when it comes to electrical issues, but am learning and that definitely helps! I will do that soon. I don't know that that would explain the killing of the battery though, would it? Thanks guys. Edited August 18, 2011 by ttodhunter Quote Link to comment Share on other sites More sharing options...
dexter72 Posted August 18, 2011 Share Posted August 18, 2011 Disconnect the battery until you have time to find the draw. If you arent able to find it, keep disconnecting the battery so you don't kill it. If all else fails you can put a quick disconnect on the battery also. Quote Link to comment Share on other sites More sharing options...
NewZed Posted August 19, 2011 Share Posted August 19, 2011 red to red, black to black; what gives? The red cable does not always mean positive on these old Zs. Have you confirmed that red is connected to the starter solenoid lug and that black is connected to a starter mounting bolt (the common positive and negative connection points)? Quote Link to comment Share on other sites More sharing options...
ttodhunter Posted August 19, 2011 Author Share Posted August 19, 2011 The red cable does not always mean positive on these old Zs. Have you confirmed that red is connected to the starter solenoid lug and that black is connected to a starter mounting bolt (the common positive and negative connection points)? Yeah, I actually double checked before I posted this. The ground wire (black) has a wire that mounts to the firewall and the base of the starter. But I did notice a red wire coming off of the negative lead... I do need to make sure it's understood that it is not only draining the battery, but destroying it to the point where it will not conduct electricity. Thanks again guys. Quote Link to comment Share on other sites More sharing options...
NewZed Posted August 19, 2011 Share Posted August 19, 2011 (edited) Have you "upgraded" to an internally regulated alternator recently? When I did my 76, I found that the common rewire procedure that I used left the "brake warning lamp check relay" activated all the time. It would drain the battery within a couple of days. Edited August 19, 2011 by NewZed Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted August 19, 2011 Share Posted August 19, 2011 (edited) Bad alternator diode is a fairly common "snake in the grass" type of problem.. Edited August 19, 2011 by cygnusx1 Quote Link to comment Share on other sites More sharing options...
getoffmyinternet Posted August 19, 2011 Share Posted August 19, 2011 place a digital multi-meter between the battery negative post and the ground. Your amperage should measure under 35 mA or so. If it is more, then you have a drain some place. Whatever you do, do NOT set the meter to amperage in series, unless it's just a harbor freight meter; in that case by all means. I like the diode suggestion. My first thought is something to do with the alternator, because simple draw will not just kill a battery unless we're talking a massive short that would probably cause it to explode, batteries are supposed to be able to go dead and recharge right back up (unless it sat dead for a long period of time). I can't imagine it's hooked up backwards and the car is still starting either but I can't say I've ever tried that... If there's a short the battery will get really hot just sitting there and if the alternator is the assassin it will get really hot while the engine is running. Otherwise it's a combination of drawing till dead and sitting dead for too long. If you aren't driving it for a while disconnect it and even hook it up to a tender. A completely dead battery can reverse polarity and trigger a charger to say it's connected improperly, and if it's been dead long enough to corrode internally then it will just read open. It doesn't take much to discharge a battery over the course of weeks. Stereos, alarm systems, etc. draw small amounts 24/7. Quote Link to comment Share on other sites More sharing options...
beermanpete Posted August 19, 2011 Share Posted August 19, 2011 It is possible the batteries are still good and your charger is not able to cope with a fully discharged battery. Some chargers will not start without a small voltage present. This is a safety device. It helps prevent a spark and explosion when connecting the charger. Some chargers also have push button to get them started after connecting to a "dead" battery. To test the key-off battery drain without risking the meter, place a small 12 volt light bulb in series with the battery cable. If the drain is acceptably low the bulb will not light. If the drain is high the bulb will light a little bit. A short will light the bulb to full brightness. If you get a good result with the bulb and still want or need to measure the drain and are worried about damaging the meter connect the bulb in series with the meter and the battery. The bulb will limit the maximum current and prevent a meter burn-out. Use a bulb that has a normal operating current within the meter's current range. Quote Link to comment Share on other sites More sharing options...
tecreatta Posted August 19, 2011 Share Posted August 19, 2011 I'd say a blown diode in the alternator just as cygnus said above. I've had it happen in multiple cars. Never ever trust color code on these old datsuns. I found that out when I did the maxima 90 amp alternator upgrade to my 280zx. Quote Link to comment Share on other sites More sharing options...
Austin240Z Posted August 19, 2011 Share Posted August 19, 2011 Agreed, I've dealt with hundreds of dead batteries, bad cells, bad alternators and the like. For a battery, especially a new battery, to be so messed up and so dead that it will no longer even register to a battery charger would require backwards flow that you'd get with a blow diode. I've also seen a bad voltage regulator do similar things to a battery, but typically it'll boil itself out, blows most of your fuses, and fries a lot of your bulbs in the process. Most Auto parts stores have free alternator testing, on the car and off it, that will be able to tell you if the diode is blown. Quote Link to comment Share on other sites More sharing options...
ttodhunter Posted October 7, 2011 Author Share Posted October 7, 2011 I did replace the alternator and everything seems to be operating properly. Thanks for the input. Quote Link to comment Share on other sites More sharing options...
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