Thoughts on this strange charging system problem?
 

Today when I took my '82 Turbo out for a drive, I began smelling a plastic-melting-smell. I traced it to the fusible link that I think connects the battery to the alternator (all I know is, when I disconnect that link, the stereo loses its backup memory), which had gotten so hot, it melted the red loom wrap on it.

Other than the hot fusible link, the real indicator of trouble is that the Charge system warning light comes on. However, I'd driven it over a hundred miles today, stopping at several places, and my voltmeter consistently showed normal voltage when the car was off (battery), and normal, fluctuating voltage when the car was running (alternator). Heck, I even did a mountain run and dynoed it today in this condition and there was no effect on performance. So the alternator doesn't seem to have any problem powering the car and recharging the battery.

Here's the strangest part: when the car gets an additional load on the electrical system, like headlights, foglights, revving over 3000-ish rpms, and/or electric engine fan, all the other warning lights (Fuel, Parking Brake, and Door ajar) come on too. But when I let the rpm's drop down to 1500-2000 rpms (ie pushing in the clutch or coming to a stop), those three warning lights shut off again, until the next time a load happens.

So I replaced that fusible link that was heating up, but it didn't solve anything, suggesting that was just another symptom rather than the cause. Any ideas? Nothing had changed on the car since I drove it back from MSA, and it handled that trip just fine. Thanks guys.

you're plagued by it too huh. May be a sign of the alternator on it's way out. Lose belt, a short in the wiring or something. I'd guess a short due to the wire getting so hot. Plainwhite Z said his idiot lights kept coming on and found the alternator connections, + and - needed to be tightened up more. What was the fluctuating voltage hovering around?

Tonight I discovered the voltage seems to be a bit higher than usual at 15.9V when I've got it anywhere above 2000rpms. Maybe it's the voltage regulator?

I know that the Haynes guide has you measure the voltages at the alternator terminals it said if voltage is higher than 15.5 at I forget what RPM that it's a defective regulator. So I'd say it sounds like it.

It is a defective regulator OR you have too much resistance in the signal wire to the regulator. If it is not receiving the actual voltage of the battery, it will over excite the alternator, and overcharge your battery. You will be lucky to save the battery if it runs like this for very long. It will melt and fuse plates in the battery together, shorting them out, and you will have dead cells. Thus resulting in a battery that maintains a low voltage, and poor CCA.

Voltage
 

So yeah i'm having trouble as well i'm not getting any idiot lights but my voltage reader says like over 18 amps when I give it gas, when i'm at a light it drops down to 14 and at night when i have my head lights on they get brighter when i'm driving then when i come to a stop they dim down...
For a little while it was reading like 14 amps then down to 12 normal.. and every now and then it reads that again but not often at all.whats up with that?

That's not amps. That's volts. Put a real volt meter of some kind on there, and check initial battery voltage, then when at idle, and then at 2500rpm's plus. You should not see over 14.6volts ever. If you do your alternator is overcharging, and will kill your battery.

Yeah, backhousez, your volt reg. is definatly going. I cooked a battery like thatpretty well. Also, this is for heat rave r, check your grounds. I fried the same fusible link when first replaced the alternator in my car becasue some coolent from the bottom radiator hose had dripped into the alternator and screwed everything up because the grounds were no good.

A bad voltage regulator means a noew alternator unless your confident enough with electrical to take the alternator apart and plug a new one in. I wasn't.

Just get a new one from a 280ZX and then you will also have a warranty from most places.

Alright, thanks guys. I have an alternator on the way, and will hopefully arrive in time for me to work on it this weekend. While we're on the subject, if I remove the metal undertray/splashguard thing, will I be able to fit the alternator between the radiator and the engine to get it out? With the power steering pump and radiator hose in the way, I can't get the alternator out through the top.

You can get it out through the top. You just have to twist it the right way. I used to burn through stock alternators every 6 months when I was running a 2300 watt RMS stereo and two 500k candle power "driving" lights in my first 1980 280ZX. My neighbor used to own an alternator/starter repair shop and he always kept one ready for me when I'd burn out too many capacitors. I got to the point that I could swap them out in about 10 minutes through the top. 5 minutes out and 5 minutes back in.

Or just unbolt the power steering pump from the head and kind of move it out of the way. I need to figure out lww's method as that would make life even easier.

wow 5 in and 5 out. Thats pretty quick. I've got it so I can get it out in 10 but back in is a pain.

Hehe, does that mean you can do it for me then? :064: j/k So you're confirming that even with the power steering pump and lower radiator hose still in place, I can still pull out the alternator from the top?

I took the block end of the lower radiator hose off and stuck a rag in both openings.

a littl emessy the first time but it gets things done. Of course that is how I accidently leaked a bunch of coolent into my first new alternator and ended up frying a fusible link becasue the grond was no longer effective.

Or like I said, just unbolt the power steering pump bracket from the head, then you can move it out of the way and the alternator can easily be pulled out through the top, but it sounds like lww doesn't need to remove anything other than the 3 bolts holding the alternator in, the hotwire, and ground for the alternator.

Interestingly enough, I've been cleaning out my garage and I happened to compare the size of the alternators I have in stock and it looks like there are two different sizes. The original stock one is about a 1/4" thicker and a 1/2" inch wider diameter than the aftermarket one. That half inch seems to make all the difference. So, if you have the original factory one, you'll probably have to unbolt the power steering bracket like duowing said.

My advice was slightly incorrect, I meant to unbolt the powersteering pump from the bracket, rather than the bracket from the head.

Interestingly enough I pulled out my new not even a year old alternator today, took that and the original 25 year old alternator from my ZXT to the auto store, they tested them. Both tested good. Oddly though the newer one, that was bought around last August made a good bit of noise, sorta sounded like bad bearings and the guy at the auto parts store mentioned that it sounds like the bearings are going bad. Also for not even being on there a year the power wire terminal for the alternator was all completely rusted over. There was a slight bit of clean metal, but not much. I went ahead and put in the original alternator that came with the car, and made sure to take some sandpaper and really clean up all the spots on the old one which looked better. Hopefully everything will work a bit better.

Hehe, goddangit, it's too late now! :icon_axe: I had a hell of a time trying to reach all three 12mm bolts that secured the whole assembly to the block, and then when I finally got it off, there's some idiotic hole behind it that leaks oil for no apparent reason. The kicker is that I ended up having to go under the car anyways to pry off the hardened rubber cap over one of the alternator wires. So I took off the PS pump for no reason and now I wonder if it's back on good enough not to leak oil from that pointless oil-leaking hole behind the bracket.

Well, at least the good news is that the warning lights no longer come on. :038: And hopefully neither the battery or anything else got permanently damaged from that day I drove the car all around in this condition. Thanks for the help guys!

There's something going on though. I mean a bunch of people had alternator issues show up all at once...odd

Glad that you got it worked out. Yeah that hole is for some reason something that stayed with the casting. It was the hole they'd use for the secondary fuel pump on the Carbd 240-260Zs and apparently Nissan must have kept using the same casting for the heads as it retained that hole for the fuel pump.

Its a conspiracy. the government must be trying to take our z's out of commision by sabatoging our alts. thats gotta be it.

I'm still surprised though that the terminals on the rebuilt alt, haven't even had it in the car for a year were almost entirely rusted over, what sounded like bad bearings, all while the original alt that came on the car and saw about 92k miles was still in pretty good shape.

I originally changed out the alternator thinking it was the problem, only to find out it was the result of a bad connection at the battery terminal. Then a year later this alternator issue shows up.

When I installed the new alt, I made sure to spray the wire terminals with electronics cleaner and gave em a good brush scrubbing.