Nismo280zEd Posted January 26, 2004 Share Posted January 26, 2004 anybody? I've rewired the old 280 from fire damage. Is there anybody that is really good with electronics.. i need some help diagnosing possible battery drains. Thanx. Ed I can draw up how i have it wired on autocad if anybody likes. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted January 26, 2004 Share Posted January 26, 2004 I am definitely not an electrical engineer, but I've diagnosed battery drains before. Easiest way to narrow it down is to disconnect the neg terminal and attach your voltmeter to the cable and the battery post. Set it to milliamps, and you can see the draw. Then start pulling fuses, and when you pull one and the draw drops, you will at least know which circuit the draw is on. Then you can trace it down from there. HTH, Jon Quote Link to comment Share on other sites More sharing options...
A. G. Olphart Posted January 29, 2004 Share Posted January 29, 2004 As another non engineer (differential calculus was a bit much) may I suggest disconnecting the hot lead of the alternator overnight & seeing if the drain goes away. (If a diode dies it can drain your battery pretty fast... obviously for this test the battery must remain connected). Once you are sure the alternator isn't the problem and if you need to drive the car, just pull the negative battery cable each time you shut the engine off. Assuming that your battery is good and that the charging system is in fact charging, this should allow you to use the vehicle. A bad leak/drain may even give you a little spark when you pull the cable. Were I to use a meter to check for current draw, I'd start with the highest ampere setting on the meter and work my way down (trying to avoid blowing a meter or meter fuse in a relatively high current drain situation). Chances are fair that if your wiring were the problem you would have warm wire(s) and/or melted insulation. Quote Link to comment Share on other sites More sharing options...
dmyntti Posted January 29, 2004 Share Posted January 29, 2004 What I usually do is connect a couple wires to an extra headlight and connect them between the battery and ground cable. Point the headlight at the winshield so that you can see the light when you are working under the dash then just disconnect fuses until the light goes out. Once you know what circuit you are looking for you can backtrack the wiring disconnecting things in the circuit until you find the problem. The last one I did turned out to be an internal short in the alternator (probably the diodes as mentioned before). The most common problem I have found is a wire getting pinched by something (like a battery sitting on it) or being cut where it goes through sheetmetal. Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted January 30, 2004 Author Share Posted January 30, 2004 like i said i rewired the Z, previous wiring got toasted from fire. everything from the firewall forward is new and larger gauge. You might be on to something with the altenator. Hey... does your volt gauges always have power in your car? mine does. Anyways i upgraded the altenator again to the 95 nissan maxima dohc puts out like 235 amps or something ridiculous like that but it works fine when i'm driving. Maybe too much power to the battery? my gauge does read about 15-16 volts on the highway. I don't quite understand how to test with the voltmeter... i put one terminal on the battery positive and the other on the circuit? let me know... -Ed Quote Link to comment Share on other sites More sharing options...
JMortensen Posted January 30, 2004 Share Posted January 30, 2004 Pull the neg cable off. Connect your red or black lead (doesn't matter)from your voltmeter to the cable and the other lead to the battery terminal. If you want to be safe, do like Olphart said and start with amps and see if there is any reading. The reading shows the draw on the battery. If it is .001 or something switch down until you get a nice big number. I seem to remember that under 100 milliamps is OK, but I could be wrong on that, since it's been years since I've had to trace a draw. If your amp gauge is constantly giving a reading even with the key off, that is at least part of your problem. I don't know how much amperage the gauge takes, but it is likely to be more than enough to drain a battery overnight. Jon Quote Link to comment Share on other sites More sharing options...
A. G. Olphart Posted February 1, 2004 Share Posted February 1, 2004 Ed- Unless you have a polarity sensing electronic meter, it is always a good idea to start out with a higher scale than you really need. If you hook things up backwards, the meter tries to go the wrong direction (generally into a limiting pin). On a higher scale the needle doesn't bounce as hard. Voltage is the electrical equivalent of pressure, and is often measured in reference to 'Ground' (in a car, that is the car body/frame). Modern cars are negative ground (-) conventionally the black lead. You put the red (+) meter lead on the circuit you are checking, and if you read battery voltage there, it is "Hot". With a volt meter you are looking for circuits which are still "Hot" when they should have been disconnected by the ignition switch. (Note that not all circuits are necessarily turned off by the ignition switch). What you are really interested in finding, however, is not voltage, but current (the electical eqivalent of fluid flow), which is measued by inserting your Ammeter in line, so that it is part of the circuit. If you have a good sized current flowing when you have everything turned off, Don has given you an excellent troubleshooting hint. Much easier to see if a light goes out (you could also use a smaller 12 volt bulb) than to try and read an ammeter each time you pull a fuse. HTH, sorry if you already know this stuff. Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted February 1, 2004 Author Share Posted February 1, 2004 yeah that's ok... good info for future Z enthusiasts craving info. I have an electric voltmeter so it really doesn't matter if it's hooked wrong etc. Anywas the whole problem is getting mine from houston when i'm 600 miles away in lubbock... don't have a spare light to hook up either. Thanks though.. i'll figure something out -Ed Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted February 11, 2004 Author Share Posted February 11, 2004 aight, luckily in this small town they replaced my battery for free without a receipt (left that in houston 600 miles back) bought a voltmeter, stuck the battery in the car, ran it for a little. then killed it. The volt gauge reads just under 16volts while running. I disconected the hot leads on the Altenator, so we'll se what happens. -Ed Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.