I tried search but suggestion go all over the place so I need a fresh perspective. Problem crept up out of nowhere. You know what it's like, you're tinkering with one thing and something unrelated starts having issues. I don't think I did anything to alter this setup.

Standard setup.....The alt light is on when the ignition is off and it's draining the battery overnight. When I turn the ignition to on the light goes off before I start the car. If the battery is charged the car starts right up. Not sure "where to check for the grounds" as other threads say.

Alternator is charging. I get 12.5+ across the battery when the engine is running. I can also hear the alt humming when it's running, the humming stops when I unplug the VR. I have checked all the wiring, redid the harness wires from the alternator to the relay board, I have two new voltage regulators. i'm trying.

Starter and battery wired correct, hasn't changed. The blue wire on the alt light is Hot when the ignition is off. Ignition on, the blue wire loses power and the other side of the light (red wires) goes hot....the light goes off...but haven't started the car yet.
puzzling....

12.5 volts from your alternator is inadequate. You should be seeing somewhere between 13.5 and 14 volts at the battery terminals. So, I suspect that your alternator is bad and in need of replacement.

Could this be an ignition switch problem? My electrical expertise amounts to nothing but asking questions.

My electrical knowledge is par with yours volts, amps, watts, hertz.....it all hurts.

It could be the ignition switch is "bleeding power". How can I check this without pulling it all out? Is there a wire that would be cold that is now hot with the ignition off?

addendum....schematics are great but my eyes just can't read them so any "Electrical Troubleshooting for Dummies" advise would be greatly appreciated.

It may be the old analog type sears meter I have showing everything a volt or two lower. Will get a new meter at lunch today.

Can the alternator be "bleeding" when OFF as well or is that type of thing switch related?

There is nothing wrong with an "old" analog volt meter. To check out the meter simply measure the voltage at the terminals of the battery with engine running and with the engine shut off. With ignition "off" you should be reading slightly less than 12 volts. Then without disconnecting the meter, start the engine and observe the metered voltage. Voltage with engine running needs be 1.5 to 2.5 volts greater than the battery voltage observed with ignition off. This test will also prove out your meter.

If I remember, the alt light on with no key is a sign that one of the diodes in the alternator's diode pack ("rectifier"?) is bad. It's letting current from the battery to go to ground through that bad diode; the current flow causes the alt light to illuminate (dimly). It can definitely draw down a battery over night.

A failed diode in the voltage regulator can cause the alt light to go on. Regardless, you will need to replace the regulator (if one can be found) or replace the alternator which has the regulator attached.

Sounds like a bad diode in the alternator. Draining battery, low charging output, and backfeeding the light. (Although I admit I'm not sure where the light is getting it's ground.) A noisy alternator is never a good thing either. Maybe put your meter on A/C volts and see what you get. Normally you would only see a few mV A/C.

type 4 alternators do not have an internal regulator

Dang it! I type slow....

Went out and got a new meter. shows here attached to battery and disconnected from the car through negative terminal kill switch. I turn negative on and volts start dropping slowly.
I start the car and the meter starts going erratic. 13.25 - 13 - 2.4 - 4 - 13.56 - 12 - 3.2 etc.

Up and down, up and down. So I think it's charging through all that....should it show a smooth voltage display?

Click to view attachment

Is there someone close by who can lend you their voltage regulator? Try one that you know is working properly and if you get proper voltage, then it's time to get a new regulator. When ever I trouble shoot electrical problems, I always try the easiest things first. It's really easy to swap out voltage regulators.

So, the 914 uses an external voltage regulator. Fine. Are they available? Certainly should be less expensive than an alternator.

To me, it sounds as though the voltage regulator is at fault. An alternator just produces voltage which it uses to push current out to a voltage regulator. Voltage regulators can be internal or external to the alternator. Apparently, you have an external voltage regulator.

At any rate, the voltage regulator does just that.....it regulates the voltage to the battery. To high a voltage, and the battery will overheat and you will begin to loose battery fluid to evaporation. To low a voltage, and the battery is not charged. You need just enough voltage to push current into the battery. That "push" is usually 1.5 to 2.5 above battery voltage. Which means that the voltage regulator should hold the voltage level to about 13.5 to 14.5 volts for a 12 volt battery.

Think of a water hose. Water pressure in a hose is just like voltage in a wire. You need water pressure to push the water through the hose. The more pressure, the more water that flows. Think of the volume flow of water. The electrical counterpart is amperage. So, amperage is the amount of electrical current pushed through a wire. The driving force to push the current through the wire is the voltage drop across the wire. So, the "voltage regulator" in your car's charging system establishes the force to move current into the battery, which drives the recharging cycle.

I just took a look at Ebay for the 914 regulator. Looks like you can purchase one for about $20 to $40. A lot cheaper than an alternator. Suggest you consider replacing the regulator first.

That's not normal. Voltage across your battery will vary slightly depending on amount of charge in the battery. However, it should never be erratic as you have stated. Again, the voltage regulator is suspect.

The diodes in the alternator convert the voltage produced by the alternator from a sine wave into a bumpy but more steady "positive" voltage. (It flips the negative lobe of the sine wave up into a positive lobe.) A capacitor in the circuit fills in between the lobes to some extent, producing a fairly steady voltage with some ripple.

A failing diode can produce wildly varying voltage such as you are seeing. Rebuild or replace the alternator.

It is very often a good idea to replace the voltage regulator any time you replace (or rebuild) an alternator.

Do both, your problem should be resolved.

--DD

My money is on a bad regulator.

At the bulb you have two wires.

one wire from the ignition turns hot when the key is turned on.

The other wire from the regulator is negative (less positive) when the engine if off and hot when the engine is running.

when the two wires are both hot (12v+) the light will turn off. If your light is on, the circuit is getting a hot from the regulator when it shouldn't and sourcing a ground ( not true ground but less positive) through the ignition switch causing the light to tun on when the key is off.

Replace the regulator.

+1

Senior moment

well two new regulators I have are acting the same....the alternator is making loud whining noises more than ever before....I guess it's time for the alternator to get up to date. Have to find a good pictorial on how to change...i'm not looking forward to doing this on a garage floor....

Is there any way to isolate the switch and the alternator to see which one is bleeding?

Changing the alternator is not hard. You have to remove some cooling tin and do some reaching around but not really difficult. I've seen it done in a parking lot more than once.

thx Elliot, yup started loosening things up per McMarks how to thread...I'll get under the car this weekend. I should start looking for new harness. Is there a go to for the alternator harness assembly? Jeff Bowlsby?

It's in! The new Bosch alt is in its place. This is official word that a home grade mechanic can change the alternator, by him/herself with one jack stand, and a few tools without removing any tin.
Follow McMark's article and you will not have to remove any tin. I just loosened up the two pieces around that corner and I was able to move the tin around by wedging a bar in and prying away just enough to slip in the pulley end of the alternator.
I did it little by little over three days....about an hour a day. no it's all put together and i'm getting 13.5 volts across the poles when the engine is revving.

Trickiest part was lining up the bracket by myself. i used allen wrenches to act as a hanger while I lined up and bolted in the main bolt. Then I did the second side and adjusted the belt tight.

So I'm the road again.....may make it now to the RM Swap. Thank you guys for you help!