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Old 02-24-2018, 01:58 PM   #26
rwb
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Originally Posted by ZVOLV View Post
Test lamp to exciter wire. Excited?
Voltage regulator didn't seem to fix my problem.

Exciter wire has 12v and continuity to D+ terminal. 14.6v regulator is installed, I'm still only getting 12.6v off the back of the alt.

Battery, with car off, has 12.9v. With car running, 12.6

Anything else I can check or is this alt toast?

EDIT: Also, I realized earlier that my exciter wiring had never been correct- I had one leg going to ground, and the other to D+, so it hasn't been "excited" at idle in a while. There's no way having that wired that way could fry anything, right? I wouldn't think so...

Last edited by rwb; 02-24-2018 at 03:20 PM..
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Old 02-24-2018, 03:35 PM   #27
dl242gt
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If it is a twelve volt bulb you probably didn't hurt it with that wiring setup for the charge light. It is supposed to go from battery + to alternator D+ to provide the exciter function. It takes a round about path through the ignition switch then cluster light bulb and on to the alternator D+.

If you never revved the engine up high enough (about 4k rpms) to naturally cause the excitement and start charging that may be why you only measured battery voltage on the alternator. Try wiring the charge light correctly or rev the engine to over 4k to cause it to self excite then measure on the battery for charging voltage.
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Old 02-24-2018, 04:46 PM   #28
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First of all, thank you.

Wiring the charge light correctly per se would be difficult, because I have no dash or gauge cluster in the car right now. I'm using a random cluster light fed with a +12v wire from the ignition switch, out to the D+ on the other, so D+ should be getting just under 12v.

There are 2 red wires coming from the ignition, both are hot whether the key is in position 2 or the car is running; they seem redundant. I am using one of these.

Picture

The light is near the positive terminal block thing, with the brown wire which turns into the red wire out to the battery. So hot in, exciter out. Can I make this more correct considering what I have?

Unfortunately I did not rev it out to 4k earlier when testing, it has no exhaust so it's impolite, but I'll do it tomorrow if need be. I already took the alternator out but it can go back in.
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Old 02-24-2018, 05:09 PM   #29
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If you already have the alternator out you can take to a zone for free testing. That seems like it should work as an exciter setup.

You should measure 12v on the wire at the alternator between that wire and ground at D+ with the key on the wire disconnected from the alternator. Then it should be lower like 1.5v or so when you try it connected just key on and the light should be on.
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Old 02-26-2018, 05:09 PM   #30
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Like I say....slap 12v to the exciter terminal wire once and it should excite the alt.

Have you tried voltage drop tests on the wires? Especially the ground wire; the wire corrodes in the crimp.
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Old 02-26-2018, 05:30 PM   #31
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Got in the zone with the alt, they said it spit out 14.8v on their rig and everything tested out fine.

Pretty sure the exciter is getting what it needs, because the light that's inline is lit at all times, getting its 12v from that terminal.

The only wire I really tested however was the exciter, only wiggle checked everything else, so will do a drop test on ground and others when I next see the car.


Quote:
Originally Posted by dl242gt View Post
If you already have the alternator out you can take to a zone for free testing. That seems like it should work as an exciter setup.

You should measure 12v on the wire at the alternator between that wire and ground at D+ with the key on the wire disconnected from the alternator. Then it should be lower like 1.5v or so when you try it connected just key on and the light should be on.
Just so I'm sure I understand: With exciter disconnected from D+ on the alt, and the key in the on position, I should measure 12v between the exciter wire and the ground, and that is what will drop ~1.5v when the exciter is reconnected to alternator?

EDIT: Also, when I say I had 12.6v at the back of the alt, this is testing VDC between the hot post and ground, with the car idling. Am I doing this correctly? If the wiring is correct such that the alt is "excited," I'm not sure how or why this would show less than the alt is able to produce, which is apparently 14.8v. Bad ground could cause this, here?

Last edited by rwb; 02-26-2018 at 09:03 PM..
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Old 04-07-2018, 11:19 PM   #32
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I finally put the alternator back in the car earlier, thoroughly cleaned the ground chain (will do a better job on the hot stuff tomorrow morning) and I'm feeling a bit stupid, because it still doesn't work and I basically still have the same questions.

When the car is running at idle, I have the exact same voltage at the exciter as I do at the hot terminal, and the battery. I thought the voltage would be slightly lower at the exciter because of the light in-line, but not dwelling on that (unless I should,) it's enough to excite, thus making a nice 14.7 volts available at the terminals on the rear of the alt, right? I get 12.36.

I'm going to give it some revs tomorrow to see if that changes anything, but A) I'm not expecting it to because it saw significant load while failing to make voltage last time it drove, and B) if it does, why doesn't the exciter work?

If autozone got 14.8v out of it, I should be able to as well, right?
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Old 04-08-2018, 01:01 PM   #33
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Try running a redundant ground from the case to the engine or batt negative using jumper cables or large guage wire.

Have you done voltage drop tests?
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Old 04-08-2018, 05:42 PM   #34
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Might have figured it out, and boy, it's stupid if true.

Last time I drove the car, the alternator was not charging the battery, and the battery died, this is known to be true. I took the alternator home with me, and between then and now, replaced the voltage regulator, then had it tested (successfully) at the zone.

While all that was happening, that battery (a big, high-amperage marine battery) was charged fully outside of the car.

So yesterday, I arrive, install the alt and battery, and start ****posting here and tearing out hair because the alt isn't making 14+ volts or any amperage at idle. Using a 100A battery tester showed almost no voltage drop on this battery, both while it was connected and car running, or outside.

Then, we decided to throw in a known dead-ish battery, started the car using a booster, and boom, 14.8v at idle. Engine bogs significantly when load is applied to this battery while car is running, and voltage does actually drop.

It seems like the battery being as full as it was meant the alt wasn't getting enough load to actually send out what it would normally, and basically I fixed it with the voltage regulator.

If this makes sense, then so it goes. If this sounds bizarre, I'm open to hearing alternative theories.

Last edited by rwb; 04-11-2018 at 08:19 AM..
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