Git-y-up Posted August 23, 2011 Share Posted August 23, 2011 Hello everyone. Need help diagnosing an electrical problem with my 1975 280z. I have installed new HID projectors sourced through ben1080(great chap). My voltage at idle is a good 12.5 V. The problem starts when I turn on accesories like my marker lights; voltage drops to 12.3-12.17. When I turn on full headlights the voltage drops again; 12.01. If I leave all accesories on at idle long enough(10-15 mins) the voltage drops low enough that my idle drops from 800rpm to 500 rpm and the engine stalls and won't start without a boost. I can understand that electrical problems can be hard to diagnose, but id be very appreciative if I could get some help. Thanks hybrid. Quote Link to comment Share on other sites More sharing options...
Oddmanout84 Posted August 23, 2011 Share Posted August 23, 2011 There are several alternator upgrades documented within this forum, and linked to from this forum. That's essentially what you need, a higher output alternator. Quote Link to comment Share on other sites More sharing options...
zack_280 Posted August 24, 2011 Share Posted August 24, 2011 You might also want to consider a larger gauge wire for charging and for feeding your accessories. Quote Link to comment Share on other sites More sharing options...
Git-y-up Posted August 24, 2011 Author Share Posted August 24, 2011 Thanks for the quick reply oddman. If i wasnt having this problem with my original Halogen's how are lower power consuming HID lights going to tax my altenator? Quote Link to comment Share on other sites More sharing options...
Git-y-up Posted August 24, 2011 Author Share Posted August 24, 2011 Im using 16 guage for the HID + and - feed wires Quote Link to comment Share on other sites More sharing options...
dexter72 Posted August 24, 2011 Share Posted August 24, 2011 You posted that your voltage at idle is a good 12.5v. That is not a good voltage to start off with, 13.0 or higher is. 240z-280z alternators do not put out a lot of charging voltage to begin with, You need to upgrade your alternator. There are quite a few options. Quote Link to comment Share on other sites More sharing options...
Tony D Posted August 24, 2011 Share Posted August 24, 2011 13.8 nominal... And where are you measuring that at??? Read JeffP's 'Extreme 280ZXT' webpage on 'alternator' and see what he went through to get consistent voltage AT IDLE (where you generally are running on BATTERY ALONE) from his charging system. Quote Link to comment Share on other sites More sharing options...
Zmanco Posted August 24, 2011 Share Posted August 24, 2011 If I leave all accessories on at idle long enough(10-15 mins) the voltage drops low enough that my idle drops from 800rpm to 500 rpm and the engine stalls and won't start without a boost. A healthy battery should be able to restart the engine after running alone on battery for 10-15 minutes. So either the alternator isn't fully charging the battery, or the battery is at the end of its life. Quote Link to comment Share on other sites More sharing options...
Noddle Posted August 26, 2011 Share Posted August 26, 2011 13.8 nominal... And where are you measuring that at??? Read JeffP's 'Extreme 280ZXT' webpage on 'alternator' and see what he went through to get consistent voltage AT IDLE (where you generally are running on BATTERY ALONE) from his charging system. http://www.angelfire.com/extreme/280zxt/page26.html Quote Link to comment Share on other sites More sharing options...
Miles Posted August 26, 2011 Share Posted August 26, 2011 If the car is drivable take it to an Autozone, Kragen etc and have them check the alternator and battery. One or both may be bad. They should be able to test both if they are out of the car as well. Quote Link to comment Share on other sites More sharing options...
Git-y-up Posted August 28, 2011 Author Share Posted August 28, 2011 Thank you gents for replying, currently I will be testing both alternator and battery. 65 amps doesn't seem alot for a stock car to run any other accesories. Thank you for the links, Ill revive this thread if I need to. Quote Link to comment Share on other sites More sharing options...
rejracer Posted September 2, 2011 Share Posted September 2, 2011 I'd never seen Jeffp's writeup, thanks for the link. KTM and I did alternator upgrades both using the GM CS144. My writeup: http://forums.hybridz.org/index.php/topic/99528-240z-charging-system-upgrade/page__p__933113__fromsearch__1#entry933113 KTM's writeup: http://forums.hybridz.org/index.php/topic/67531-ac-delcogm-alternator-swap-part-2-cs144-installation/page__p__634683__fromsearch__1#entry634683 Both are good upgrades, I'm a bit partial to mine as it requires no machine work, and I think the end result is a wee bit more solid of a mount. I am running a stock dampener and a slightly smaller diameter alternator pully. I have my idle set to 800ish and the lights dim ever so slightly at idle. I have to be paying attention to notice it. At Idle I think it's producing 13.2v, and at 1500 Rpm it's at 14.45v and stays there with higher rpm. If I lower the idle to 700 rpm (where I like it) the voltage drops to more like 12.8v. I'll have to do some more testing to be sure, but that's my recollect of how it works. Overall it's a great upgrade. The really big advantage to going with a CS144 is you can go into any auto parts store and buy one should the need arise. If you get a fleabay custom or one from Z specialties, it's downtime until you can get another custom unit. Quote Link to comment Share on other sites More sharing options...
Git-y-up Posted September 2, 2011 Author Share Posted September 2, 2011 (edited) Thanks Rejracer, You have opened my eyes to what I can do to clean my electrical mess. I am finding wires that are spliced and crimped. Now im thinking my problem could be more than Alternator related. Is there any threads out there that souly talk about cleaning and simplifying a 280z wiring? My wiring harness looks teribly tampered with. Edited September 2, 2011 by Git-y-up Quote Link to comment Share on other sites More sharing options...
Git-y-up Posted September 2, 2011 Author Share Posted September 2, 2011 13.8 nominal... And where are you measuring that at??? Read JeffP's 'Extreme 280ZXT' webpage on 'alternator' and see what he went through to get consistent voltage AT IDLE (where you generally are running on BATTERY ALONE) from his charging system. I'm metering directly at the battery with my leads on + and -. Quote Link to comment Share on other sites More sharing options...
NewZed Posted September 3, 2011 Share Posted September 3, 2011 Thanks Rejracer, You have opened my eyes to what I can do to clean my electrical mess. I am finding wires that are spliced and crimped. Now im thinking my problem could be more than Alternator related. Is there any threads out there that souly talk about cleaning and simplifying a 280z wiring? My wiring harness looks teribly tampered with. Nissan used crimped splices throughout the wiring harness at the factory. Even the untampered harnesses look tampered. Quote Link to comment Share on other sites More sharing options...
Git-y-up Posted September 3, 2011 Author Share Posted September 3, 2011 (edited) This is an example of what I mean, random wire colors and crimped connections. This is normal? DSC00498 by Crashing_Thunder, on Flickr Edited September 3, 2011 by Git-y-up Quote Link to comment Share on other sites More sharing options...
Derek Posted September 3, 2011 Share Posted September 3, 2011 One thing I just ran into. I put a 90 amp maxima alternator in a couple of years ago. My charging during the summer was always marginal. I'd have to thow a charger on it at least once a week. This summer I decided to do some checking. To make a long story short you cant run 90 amps of power through a system built for 45 amps. The route on the factory wiring on my 73 is alternator, amp gauge, fuse box, Fusable link, starter, battery. I added an extra 10 gauge wire from the alternator to the battery and the problem has gone away. Obviously the amp gauge isn't accurate anymore and at some point soon I'll be doing a major rewire job. Derek Quote Link to comment Share on other sites More sharing options...
Git-y-up Posted September 3, 2011 Author Share Posted September 3, 2011 One thing I just ran into. I put a 90 amp maxima alternator in a couple of years ago. My charging during the summer was always marginal. I'd have to thow a charger on it at least once a week. This summer I decided to do some checking. To make a long story short you cant run 90 amps of power through a system built for 45 amps. The route on the factory wiring on my 73 is alternator, amp gauge, fuse box, Fusable link, starter, battery. I added an extra 10 gauge wire from the alternator to the battery and the problem has gone away. Obviously the amp gauge isn't accurate anymore and at some point soon I'll be doing a major rewire job. Derek So basically current has to go around the world before it reaches the battery haha. I believe I have a complex issue here where more than one thing needs to be addressed to get complete healthy stable voltage at IDLE and REDLINE. Quote Link to comment Share on other sites More sharing options...
Git-y-up Posted September 3, 2011 Author Share Posted September 3, 2011 DSC00513 by Crashing_Thunder, on Flickr Quote Link to comment Share on other sites More sharing options...
Tony D Posted September 11, 2011 Share Posted September 11, 2011 (edited) So basically current has to go around the world before it reaches the battery haha. I believe I have a complex issue here where more than one thing needs to be addressed to get complete healthy stable voltage at IDLE and REDLINE. No, not on a 280Z---you have to watch out that the advice you give/get is APPLICABLE to the model being discussed. The 280 no longer used the Ammeter (which by function must have all the car's power through it to give an accurate indication of amperage draw/charge in the system.) The 280Z and 260Z used a Shunt for this purpose, keeping all high amperage wiring outside the passenger compartment. The largest issue with these cars is poor sensing line voltage leading to drift, and voltage regulators that drift. The speed of the alternator is usually not sufficient to support more than minimal loads at idle. Period. The ONLY way to up amperage is change the turns ratio of the alternator--PERIOD. Make it larger diameter increases rotor/stator arc speed to cut more turns and you get more amperage at the same speed, or put in more turns which is limited by the physical size of the alternator so you speed it up with pully ratio---the end result being an alternator turning 12K+ rpms at redline, and wires on the rotor blowing out in a spectacular fashion ... ask me how I know about that one! How you achieve the amperage you want at idle is up to you, but there are no secrets here. It's all the same situation dictated by ohms law. Then, once you solve the 'amperage' issue at point of origin then you find DISTRIBUTION to be the next weak point. Generally from fuse to accessory in most cases you don't have an issue. But the power feed line off the stock alternator (and equally important the GROUND RETURN SECTION OF THE EQUATION) is sorely lacking. Fix the ground, main power feed, and alternator power supplying capacity and most of the other stuff is a non-issue. Headlights have plug in relay upgrades, nobody powers their high-capacity stereo off the stock radio fuse... What ELSE do you really change that you don't run dedicated circuits on your own? The basic utility system in the car is darned good with the exception of grounds and switching power via ground. Fix the ground loop which everybody seems to ignore and everything works better. VW and Chevrolet were known for running ground straps on everything. Nissan doesn't have ONE on the car. The fuel tank has a dedicated ground line, that shunts to the chassis. But that's it! Pitiful. An electrical circuit has TWO components for those electrons to travel through: Supply and 'ground return'---if you concentrate all your focus on the supply side only, you make more problems down the road. Live on a boat for a while, or with a Corvette, and you will understand better! OH---And the wires you show in the photos: Not Nissan. Those are all accessories added by someone. If you haven't cut into the harness you are in for a shock. It's not much better inside, but it was functional for 30 years. Edited September 11, 2011 by Tony D Quote Link to comment Share on other sites More sharing options...
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