ktm Posted May 9, 2009 Share Posted May 9, 2009 You alternator is not charging your battery. That is one of your big problems. You say the alt was bench tested, but by who, the place you bought it from? I had an Autozone reman fail on me within 1 month of purchase. You need to buy a battery charger and tender. Your battery is nearly drained. Charging a nearly drained battery can damage alternator. Running a fuel pump on such low voltage can damage the pump. Quote Link to comment Share on other sites More sharing options...
ASenna Posted May 9, 2009 Author Share Posted May 9, 2009 Have you checked your engine bock ground? And alternator case ground? Odd and roaming current spikes tend to be ground issues in my experience. Not sure if yours has a charge light, but if you do, check and see if its coming on when you turn the key on. If its not, check for resistance from the L terminal to the alt case, if its open, somebody is lying on the bench test . Voltage isn't spiking, it's staying very steady very low ha. Someone else with a boosted 260Z suggested that I need to put in a lamp in parallel with the exciter circuit in order to put enough resistance to excite the alternator. It also functions as a charge warning light. Any thoughts to the validity of this? Quote Link to comment Share on other sites More sharing options...
ASenna Posted May 9, 2009 Author Share Posted May 9, 2009 You alternator is not charging your battery. That is one of your big problems. You say the alt was bench tested, but by who, the place you bought it from? I had an Autozone reman fail on me within 1 month of purchase. You need to buy a battery charger and tender. Your battery is nearly drained. Charging a nearly drained battery can damage alternator. Running a fuel pump on such low voltage can damage the pump. Yes... I realize this is the problem. This was from testing the voltage across the battery and the output from the alternator. I know the alternator is not charging the battery. I had the alternator tested at a different place than where it was bought. I do have a battery charger and yes it has been used. The question now is WHY does the alternator not excite when prompted to give at least 14.5V potential at the BAT connection. The results above should explain that the problem rests with the alternator receiving an excite potential without fomenting an output. The question of what is the problem has been passed. I'm trying to understand why it occurs and how to remedy it without chucking random parts at the car trying to fix it. Quote Link to comment Share on other sites More sharing options...
ktm Posted May 10, 2009 Share Posted May 10, 2009 I merely offered up the other bits of advice because your battery is low and I did not want to see you burning up other parts. You stated that with the car off, your voltage was 12.3. If you have a charger/tender, your voltage should be high 12s at least. If the lamp circuit is not exciting, then then voltage regulator could be the issue. Is it the stock 1975 280z regulator (externally regulated)? If not and you have an internally regulated alternator, then it is the alternator. Wizardblack suggested it a week ago. The circuit goes through an external voltage regulator located on the inner fender next to the alternator. Quote Link to comment Share on other sites More sharing options...
ASenna Posted May 10, 2009 Author Share Posted May 10, 2009 The alternator is internally regulated. It has undergone the swap as mentioned in this thread: http://www.atlanticz.ca/zclub/techtips/alternatorswap/index.html It has also been done correctly ( I have checked and double-checked ). I'd rather not unplug the battery while the car is running as Wizardblack suggested. I'd rather not fry things. What I believe is happening now is either the alternator is not getting enough resistance to excite it, or the diode responsible for output after being excited is malfunctioning. Either way, the data I found testing each point in the charging system does not lie and the fault should be in the alternator. Quote Link to comment Share on other sites More sharing options...
smoorhs02 Posted May 10, 2009 Share Posted May 10, 2009 I thought all pre 78 280Zs had an external voltage regulator? Quote Link to comment Share on other sites More sharing options...
ASenna Posted May 10, 2009 Author Share Posted May 10, 2009 I thought all pre 78 280Zs had an external voltage regulator? they do. This one has been converted. Quote Link to comment Share on other sites More sharing options...
philfree Posted May 10, 2009 Share Posted May 10, 2009 Hi Do you have a test light? If you do i would hook up a wire from the positive of the battery via the test light to the light terminal on the alternator with the motor running and see what it does. This should light the test light up until the motor is running then go out Quote Link to comment Share on other sites More sharing options...
WizardBlack Posted May 10, 2009 Share Posted May 10, 2009 Why would the alt fry things if the battery is disconnected? If the regulator is bad, it will damage things with the battery hooked up. If the regulator is good, the alternator will drive the electronics (as they do anyways). Quote Link to comment Share on other sites More sharing options...
The570Z Posted May 10, 2009 Share Posted May 10, 2009 If it has regulation problems as this one seems to, taking the battery out of the loop can result in crazy voltages which will burn out circuits and modules very very quickly. Have you checked your grounds yet? I didnt say voltage spikes btw, I said current, intermittent grounds can cause current to backfeed and do all sorts of weird things. Voltage will stay the same though. If the grounds are good, replace the alt, its fried. The load on the exciter circuit is is the alternator field coil, nothing else in line is needed. Quote Link to comment Share on other sites More sharing options...
WizardBlack Posted May 10, 2009 Share Posted May 10, 2009 Anyhoo, I think the OP needs to have the alternator either warranted for another one or tested at another location. It could be barely passing their test. A go/no-go test isn't the best for an alternator when it's borderline. It's probably the most time-efficient step to try and solve it at this point. I have a ZX alt (a converted one) that I don't need (went to a GM 1-wire)... Quote Link to comment Share on other sites More sharing options...
ASenna Posted May 11, 2009 Author Share Posted May 11, 2009 For now, I've remedied the problem. I went back and tested the alt AGAIN and it still showed it passing. I was still skeptical because of the diode situation. At the suggestion of another boosted Z driver, I wired a small indicator lamp into the exciter circuit. He thought that with the rewired system, like on his car, that little resistance would aid in exciting the circuit and function as a charge warning lamp in the process. After charging the battery and installing the lamp, I started the car and took a multimeter around all the connections. The output of the BAT connection showed 13.6V at idle and around 14.6 at ~2000RPM. Not sure if that's a sure-fire fix, but it runs smoother and my battery doesn't die! I still have a little bit low fuel pressure due to the new pump and not messing with the regulator and the car does start and die occasionally, so I believe I might still have a vacuum leak, but it's much better. Thanks for all the help and suggestions! Quote Link to comment Share on other sites More sharing options...
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