major issue. could use some help please

[ship2236]

My 86 has been having some weird issues. On jan 2 the starter went out on me. Easy enough of a fix of course so it was g as ndk ed tge next day. About 5 days later I noticed in the mornings when it was really cold and i would leave for work the charge and brake light would be illuminated. By the time it came to me leaving for lunch or getting off of work later in the day the lights would be off. Now I know that the lights on mean the alt is on its way out so I pushed it as long as possible before dropping tge money on a new one. It lasted until last week I was driving on the frwy n next thing the lights all dimmed on me and tge bogging started and it died. Next day replaced it w another and charged the battery and it did it again but the brake andcharge light stayed lit w this particular alt. I then took it back and of course it being a special order part tgey didnt have another so I opted to just upgrade to a mk3 supra na alt. Virtually the exact same but the plug n posts r slightly clocked diff and its a 70amp instead of 60. I also figured it was time for a new battery so that was changed aswell. Put them in the car and all lights were off and it ran for almost 2 days and then the process repeated itself now. Since then ive reswaped it w another new alt, replaced the starter again, replaced both pos term and neg terminal and wire, replaced all fuses inside the bay and the kick panel w new fuses, cleaned all my grounds and performed a draw test. I cant find anything pulling power and the alt seems to be working as tge charge light isnt coning back or anything. Once it dues it will act as if it has a dead batt. If I charge the batt or put a diff one in it the car starts w no problems at all and agter about 5min of letting it idle it will and tgen click once the battery power is depleted. I cannot find any split wired or damaged connections going from the battery harness to the alt. I need help

[jondee86]

Sounds very much like the alternator is not charging the battery at all.
The car just runs off the battery until it goes flat, and the car dies. Get
your meter and check the terminal to terminal voltage with the car just
sitting with everything turned off. Start the engine and check the voltage
again soon after starting, and again after ten minutes or more of engine
running time.

After sitting overnight a fully charged battery should be around 12.6 volts.
Once the starter has operated, the alternator will immediately start
restoring the energy used for cranking, and the charging voltage will be
around 14.5 volts, and after the engine has warmed up the charging
voltage will drop to maybe 14 volts. The exact numbers are not important,
so long as you see a couple more volts across the terminals to prove that
the alternator is actually charging.

Cheers... jondee86

[ship2236]

Thanks for the reply. It is very weird I just came in from tinkering w it again. I let the battery charge a few hrs. W tge car off its at 12.5 volts. With it running it stays the same. If i hold tge throttle around 1500-2000 rpm the volts drop around 12.1/2. Then it dies after 5-10 min n will not start via a dead battery. I just cant see that all 3 alt ive tried have been bad especially e hen onr came off of a running no prob car. Just very stumped at this point

[jondee86]

Probably nothing wrong with the alternators, the most likely problem is
that the 60 Amp AM-1 fusible link (one of the square fuses that sits right
on the battery positive terminal) has blown. Easy enough to do if you are
working around the alternator and make some sparks

Once that fusible link is blown the output of the alternator cannot reach
the battery, so no charging... car runs off battery until the battery dies.

Cheers... jondee86

[ship2236]

Ive checked the fusiblr link aswell and visually from my perspective I cant see any damage ir signs it popped but I have heard of tge end points inside melting n causing probs. Idk I guess I can try it. All I know is im sure its a small stipid issue, but she better run titts when I figure it out w all the things im replacing haha

[jondee86]

If you can isolate the link by unbolting it, check it for continuity
(zero Ohms resistance end to end)) with your meter. There are a
couple of other possibilities, but check the link first.

Cheers... jondee86

[futurehachi]

Had the same issue... I rewired my alt to single wire and ive had no issues. It sounds like something to do with the wiring to your dummy light. Try unplugging it from the alt and see what it does

[ship2236]

I noticed today there was a bit of corrosion on the fusible link fuses but they didnt look blown or damaged. I replaced them anyways and w the multimeter on the battery I was sitting around 12.5-12.8v. When I try to start the car it drops to 10v n below n cranks n cranks no start. When I charged the battery last nite it started first turn of the key. So very frustrating as im sure its something so simple

[jondee86]

When you are trying to troubleshoot problems with your car, it is always
better to tackle the problems one at a time. From your last post it seems
that you have two problems...

1. The alternator is not charging the battery, and
2. The engine cranks but does not run.

Now it is possible (but highly unlikely) these two problems are connected.
So lets go at them one at a time... first the alternator...

You have checked the fusible links, so we can say that heavy wire that
connects the "B" terminal (separate lug on the back of the alt) to the
battery positive is OK. The next wire to check is the white signal wire
that supplies battery power to the "S" pin on the three-pin alt plug. This
pin should have 12V to ground at all times when you pull the plug and test
the pin. The Black-Yellow wire to the "IG" pin should have 12V to ground
at the plug when the ignition is ON. Check these two are OK.

The yellow wire from the "L" terminal on the alt plug is the one that
drives the charge light, and AFAIK does not affect alt operation, so we
will leave that one aside for the moment.

Regarding the battery... yes, the battery voltage will drop when the
engine is cranking due to the huge current draw of the starter motor.
But 10V should be enough for the engine to start. Most likely the plugs
got fouled or some other minor issue. You could try jumping it with
another battery, or try it again in the morning with a fully charged
battery. If it definitely will not start, that is, no spark or fuel, then you
need to troubleshoot that separately.

Cheers... jondee86

[ship2236]

Problem has been found. After looking through the wiring diagrams online n getting ahold of a power probe I found that on the remanufactured alternator, the prongs on the plug for the 12v constant n 12v switch positions had been reversed wich was in turn not allowing the signal to charge bw read by the alternator. Switched them around to where they technically shouldnt be n now everything is back in running order. On the flip side, at least theres a **** ton of new things I shouldn't have to worry about changing out for a while now

Thanks you for all of the responses I appreciate the help youve tried to provide me with very much