J240ZTurbo 1 Posted July 25, 2009 Share Posted July 25, 2009 Hi, I just got a new battery is it normal if I disconnected either the negative or positive cable for my 1977 280z to turn off? Dosent the alternator suppost to be charging? Quote Link to post Share on other sites
jhm 128 Posted July 25, 2009 Share Posted July 25, 2009 No, the battery is an integral part of your electrical system. Remove it and the system fails. Quote Link to post Share on other sites
jasper 14 Posted July 25, 2009 Share Posted July 25, 2009 Most cars will run with the battery disconnected. I would NOT do it on my car. You can easily damage the alternator. Voltage spikes/over voltage can also cause damage to electronics. I don't do it on customers cars either. Some of the other mechanics at my shop do, to save time. Use a voltmeter to check your charging system properly. Quote Link to post Share on other sites
jhm 128 Posted July 25, 2009 Share Posted July 25, 2009 Jasper- Agree completely with your recommendations. But still have one nagging question....how's your car going to run if you disconnect the battery ground?? jhm Quote Link to post Share on other sites
jasper 14 Posted July 25, 2009 Share Posted July 25, 2009 First off......It does.... The alternator continues to output voltage/current. The "open circuit" causes elevated output. As to the how and why???? I would also have to google for a technical explaination. It's been a long time since I read that article.(decades) Quote Link to post Share on other sites
CrazyZdriver110 11 Posted July 25, 2009 Share Posted July 25, 2009 Jasper-..how's your car going to run if you disconnect the battery ground??jhm The electrical system has other grounds besides the battery Ground. In most cases if your car shuts off after disconnecting the battery the alternator could be bad. Quote Link to post Share on other sites
Administrators RTz 266 Posted July 25, 2009 Administrators Share Posted July 25, 2009 Juan, please use descriptive subject titles. Quote Link to post Share on other sites
HowlerMonkey 12 Posted July 26, 2009 Share Posted July 26, 2009 Never do that. Your alternator diodes will thank you. Quote Link to post Share on other sites
terrya 0 Posted July 27, 2009 Share Posted July 27, 2009 You shouldn't disconnect the battery, but under most most circumstances the car should still run. I'll admit that on occasion I have done the same to check if the alternator was working or not. Quote Link to post Share on other sites
JayBee280 0 Posted August 23, 2009 Share Posted August 23, 2009 simple answer yes it should run without battery. some science in these post. just simple answers should do Quote Link to post Share on other sites
78zstyle 0 Posted August 25, 2010 Share Posted August 25, 2010 Uh.. my z wont run if I turn off the battery... Bad alternator? Quote Link to post Share on other sites
19762802+2 14 Posted August 25, 2010 Share Posted August 25, 2010 Isn't the battery a direct power source for the ECU, so the later z guy's that have the EFI can't disconnect the battery but the early Z guy's can, or am I just wrong. Quote Link to post Share on other sites
aplyedmind 10 Posted August 31, 2010 Share Posted August 31, 2010 I totally agree with 19752802+2. Quote Link to post Share on other sites
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