Guest seth240zxt Posted March 19, 2005 Share Posted March 19, 2005 Hi all, I have a 240z with a 280zxt engine. The car runs but it goes through altinators like it cool (I've gone through 4 so far). Everytime I drop a new one in it registors about 14.5v, but after about 24 hours of running time the car starts to run like sh!t and the volts drop to about 8. I didn't do the electrical portion of the intall for I have no skill in that field. What do you guys think? Thanks for the help Seth Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted March 19, 2005 Share Posted March 19, 2005 I'm betting you're still using the 240z style alternator that uses the external voltage regulator? Chances are, your voltage regulator is bad. I had the same problem a while back... my alternators were only lasting maybe a month. Don't bother trying to replace the voltage regulator either, the only ones available now at places like Auto Zone, are commonly thought to be crap (I can vouch for this from first hand experience). One of the best things you can do is to upgrade to a later 280zx or 280zx turbo alternator, the kind with internal voltage regulator. Unfortunately, I dont have the link anymore to the website that shows how to do this... it is VERY easy to do, just a few wires you have to patch up and a one way resistor... I did the mod in about an hour taking my time, and now run a 280zx turbo alternator. Anyways, search on this forum and you'll probably find it. If you step up to the internally regulated alternator and still have the problem, than you have a short somewhere in your wiring and it's probably gonna be a pain in the *** to track down, you'll be better off taking it to an auto electric specialist. Either way you're still better off with the better alternator and should do this mod considering it is easy and very cheap to do. Quote Link to comment Share on other sites More sharing options...
COZY Z COLE Posted March 19, 2005 Share Posted March 19, 2005 http://www.zcarcreations.com/howto/voltreg.htm Read the part about if you have a 240Z or 260Z so that when you do the conversion your car doesn't stay running. LARRY Quote Link to comment Share on other sites More sharing options...
briann510 Posted March 19, 2005 Share Posted March 19, 2005 get a plug and play alternator from zcar specialties. you dont have to do anything with the external regulator except unplug it (no cutting or splicing wires in or together or any hassles of other electrical wiring mods with it, you just discard the whole thing). you dont even re-plug the stock 2 prong connector to the back of the alternator eitheras its just tapped off and left hanging or cut off. i just bought a 105 amp one for $180 and he also sells a 120 amp. he has already done the internal mods so it goes right in. no bracket or pulley mods either. plug and play alternator Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted March 20, 2005 Share Posted March 20, 2005 I dunno $180 for an alternator is pretty steep... though the increased amps are always welcome... but then, stock 280 ZXT alternator is like 60 or 70 amps... seems to be plenty for my car anyways. You can get this for $40-60 and again, the mods to get one working in a 240 are SO easy and only cost a couple dollars.... that plug and play one had better do something nifty like make you coffee or something for $180!! Quote Link to comment Share on other sites More sharing options...
Guest rick458 Posted March 20, 2005 Share Posted March 20, 2005 will the stock wiring harness handle 100-120 amps? Quote Link to comment Share on other sites More sharing options...
zcarnut Posted March 20, 2005 Share Posted March 20, 2005 As an electrical engineer, I’m not a big fan of the “plug and play†or single-wire alternator concept. I pointed out in the directions “Using An Internally Regulated Alternator†(which has been copied throughout the internet) that sensing the battery voltage with a separate wire is a much better concept. This is why Nissan did it. This is also referred to as the “three-wire†concept. Single-wire alternator regulators have to sense the alternator output and not the battery. Because of the voltage drop in the wire between the alternator and the battery when the battery is being charged the battery terminal voltage will be less than the alternator output terminal. This could result in possible undercharging of the battery. However, if you want to use a single-wire alternator then you should increase the size of the [charging] wire between the alternator and the battery. You can also add another external charging wire in parallel to the one buried inside your wiring harness. Additional reading for non electrical types (with the all important pictures) can be found at: http://www.madelectrical.com/electricaltech/onewire-threewire.shtml [Please ignore the author’s sales pitch.] will the stock wiring harness handle 100-120 amps? Good question. In a nut shell, no. The stock alternator and wiring harness is only designed for the stock electrical loads plus some small additional margin. Even using a three wire alternator with increased output requires a larger charging wire. On the Maxima’s that used the 90A alternator the charging wire diameter is larger than the corresponding one on the early Z cars. You should see the charging wire used on the Maxima’s with the 105A alternator. It’s almost the size of the early Z car’s battery to starter wires! So, if you are upgrading the alternator in an early Z car, then you should increase the diameter of the alternator to battery charging wire. Any new electrical loads (electric fans, megawatt stereos, etc.) should then be wired (through fuses!) directly to the battery terminal and not through the existing stock wiring harness. Quote Link to comment Share on other sites More sharing options...
briann510 Posted March 20, 2005 Share Posted March 20, 2005 i agree with that, and thats exactly why the instructions say to run an additial #8 wire from the alternators bat terminal directly to the + battery terminal. do not run the 105 or higher alternator just with the stock bat wire hooked to it. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted March 22, 2005 Share Posted March 22, 2005 ugh... this is news to me. So what about with the 60-70 amp turbo alternator? I'm still using all stock wiring on my '72 wiring harness (unless the guy that did the turbo swap changed out the part of the harness that connects the alternator as well? I dont really know). I think I have the 70 amp alternator... anyways been running it that way for about a year (only about 5000 miles) with no problem... should I worry? Quote Link to comment Share on other sites More sharing options...
Tony D Posted March 22, 2005 Share Posted March 22, 2005 I would agree with ZCar Nut. My first thought was 1) that your VR might be bad 2) that you have corrosion on your sensing wire. I recently replaced a "new" VR because it fried. Remember that you can have NO POWER applied unless the case of the external regulator is GROUNDED! What I did was to run a separate line (#12) fromthe case of the external voltage regulator to the star ground point on the chassis just below the battery. This modification ALONE stopped my voltage seeking problem. Before depending on what accessories I was runnning, the voltage out of the alternator would be anywhere from 12.9 to 15.3 VDC+!!! After the addition of this ONE ground line, the voltage dropped to an almost universal 13.8-14.5VDC no matter WHAT accessories were on the circuit. After finding some corrosion on the sensing lines, and making some corrections and cleanings, the voltage stabilized even further to closer to 13.8 - 14.2 VDC. The big thing is that now I have 13.8 at IDLE as opposed to 12.9 or lower before! Sensing wires and bad grounds kill electrical components. Make sure they are all up to snuff. And if you have a 260 or 280Z with the external regulator, my little #12 wire for the ground is ESSENTIAL to you not frying your reg! The thing mounts to a bracket that mounts to the chassis. That's two junctions of bolts and painted metal to corrode causing this drift. Not to mention that if you remove the bracket and it's powered on the battery (like for troubleshooting) POOF! There went that NEW VR! That Pigtail I added allows you to remove the battery and gain access to the regulator and not loose it's ground path. Preserving it for another week at least! LOL Good Luck! Quote Link to comment Share on other sites More sharing options...
Guest seth240zxt Posted March 22, 2005 Share Posted March 22, 2005 Thanks for the quick reply. To add, there was a grounding wire loose that connects to the head, I tightened it up and that added more life to my alt. Quote Link to comment Share on other sites More sharing options...
bjhines Posted March 24, 2005 Share Posted March 24, 2005 Quick Electrical checklist....for 240Zs 1. Make sure the original fusable link is in place... on the starter +terminal. 2. Any added circuits should be connected to the battery +terminal with a fuse at the battery. 3. Ground the engine block to the chassis with a heavy guage grounding strap...no lightweight body ground crap...we want to see big meaty wire. 4. make sure the battery ground -terminal has a connection to the firewall near the battery. 5. check and/or clean the lighting ground terminals in the rear clip, the dash areas, and the front clip. These are common problem areas...you might get a few more watts of headlamp intensity. NOTE: Adding circuits that bypass the original harness (attached to battery +)..... will cause the AMP guage to read a high charging condition when using the new circuits.... Just use a volts guage instead. Quote Link to comment Share on other sites More sharing options...
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