Hi guys, hope someone can help me. I bought a new alternator last year and it seems to work. I never did a testing with a multimeter. Now I did it. When the Engine is Running and i measure the battery it is only 12,3 volts. Even when I wire directly from the alternator (bat connection) to the battery (plus) the multimeter only shows 12,3 volt. But I can charge it with an external charger.See pictures attached. What is the issue???

thank you very much

 

Confirm that the test meter is accurate against another meter.
​​​If it has been running ok for a year it makes one question the meter.

If it is undercharging, it could be a bad external voltage regulator, alternator, slipping belt or wiring.
Should charge @ 13.8-14.2 VDC with a fully charged battery and no electrical accessory load. It may need an rpm increase to reach this voltage.

If you have an electrical repair shop nearby, they can test both voltage and amperage output in minutes. Both volts and amps is what you really want to know.
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Good luck!!!

 

thanks! The meter is working. Even if I connect the alternator directly (BAT and GRD) it won’t charge. When I put the multimeter directly to the Alternator (BAT and GRD) it is still 12,3 Volt.

 

I'm missing something here or someone else is missing something, also.

Post #1 - Battery reads 12.3 V via two connections while on car (supposedly charging).
You can charge the battery with an external charger (is your statement). What is the voltage on the battery when you are (supposedly) charging from an external source?
It's beyond my comprehension how anyone is supposed to make a comparison here and rule out the battery as being faulty.

I'm sorry, you need to first determine what the state is of your battery. If your battery is NO GOOD, it's quite likely you aren't going to charge a battery.
Again, what is the voltage of the battery when you state it charges from an external source?

We're comparing marshmallows to walnuts thus far.

 

when charging with the external source it is 14 volts

 

After apparently a year with no problems, what prompted you to measure the battery voltage now? What do you mean it "seems" to work? It either works or it doesn't. Are you have any problems (weak battery when starting the car? headlights dim when you put the car in gear?) Or was this just a curiosity thing? Other than the voltage on the battery being around 12.5 volts, what OTHER problems are you having or symptoms are you seeing? If none, you may be trying to fix something that isn't broken.

 

the battery was empty and the car did not start! So i performed the alternator test and recognised it is not the needed 14 volt.

 

Review the stated amperage output of the alternator. Determine what the stated amperage output is. With your car turned off, set your multimeter to AMP. Turn off all equipment in your car. Turn on your car - let it idle several minutes. Touch/Hold the multimeter BLACK (negative) wire to the negative (-) battery terminal. Touch/Hold the multimeter RED (positive) wire to the positive (+) battery terminal. Read the output in AMPS. Now, turn on the Air Conditioning (if you have it). Turn on the Heater. Turn on the Blower/Fan. Turn on the Headlights. Turn on the Radio. Read the amperage when you turn on each device. Turn them all on and then read the amperage with them all turned on. The alternator should increase its amperage output each time you turn on a device to compensate. Tell us if the amperage goes up when you perform this operation.

 

By "empty," you mean the battery was totally dead? No cranking at all. But you can charge it up with the external charger, and it will start the car?

How old is the battery? I would take it out and have it checked. It may not be able to hold a charge. If it checks out OK, it might be a bad alternator.

I see that yours is AC/Delco brand. You would think that would be a good brand, but you never know where things are made these days.

I had a situation not unlike yours with my '78 Toronado. I put in a new Duralast alternator from Autozone. Yes, I know, who the hell knows where that was made. The voltage on the battery when the car was running was never more than about 12 volts, sometimes 11.5. Even after taking a lengthy drive, parking the car, and then starting it up again a few minutes later, it would be slow to crank. The turn signals clicked more slowly than they should.

So I took a chance and bought another new alternator. But this time it was a Bosch brand alternator I got through Amazon. All I can say is, WOW. I started the car with the new alternator, and the voltage (I have a voltage gauge in the car) immediately went to 14 to 14.5 volts, and that's where it always is when I start and drive the car. The battery always has a good, full charge and starts the car easily, and the turn signals click just like they should. The new alternator made all the difference in the world.

I didn't start my troubleshooting by having the battery checked like I suggested to you because the battery in the car was only a couple of months old. Yes, batteries can be bad out of the box, but I thought that unlikely in this case.

If I were you, and if the battery is not new or nearly new, I would start by having it tested. If it checks out ok, I would then have the alternator tested. Or just throw in a new Bosch!

In me, Bosch has found a fan for life.





Anyone want to buy a nearly new Duralast alternator?

 

Just as a quick check does the battery light come on with the ignition key in the run position with the engine off. If not the alternator will not turn on to charge. it could be just a burnt out bulb

 

I see someone has changed out the plug on the wiring harness, you may want to trace those wire back. The wires should be a blue and white in that plug.
may not be anything, just something that stood out to me.

 

Amperage is measured in series with the load, this will not work at all. In addition most meters will not tolerate high amperage so its best to do all the measuring in the volts scale.

 

Interesting, it worked the several times I tested it on two different multi-meters. I didn't fry any of the multi-meters.

 

I had to validate. I have two Southwire multi-meters: 100A AC/DC and 400A AC/DC. It worked for both. I didn't look at my alternator amperage output (I may have it written down somewhere) - it's the alternator which came on the car when I purchased it. Both multi-meters read 46A.

 

As old cutlass stated, this is NOT the way to measure the alternator output. The above connections will just blow the fuse as it is measuring the current of the battery, which is hundreds of Amps (you know, that CCA rating on the battery label).

 

Again you cannot read amperage in parallel to the load, it has to be in series. In other words in order to read amps you need to remove the positive cable from the battery, connect it to the black lead of the meter, then connect the red lead of the meter to the positive post of the battery.

 

Oh buggers. I am so bad. I thought that was exactly how I had written it up. Very sorry. You are absolutely correct. I then re-read my notes from my car notebook - same write-up as you both described. I then went further into my notepad notes and low and behold, yes - both of my multi-meters have a positive terminal load "clamp" tester from which I read my amperage (last year sometime). I use my load 'clamp' mostly for AC. I forgot it will measure DC. I'll be honest, each time I use either of these multi-meters in the DC function to read amperage, I have to re-read the instructions. I just did the entire test again and placed the ammeter (mulit-meter) on the positive terminal in series to confirm my results which remain the same, but my brain is absolutely incorrect in how I wrote this up.

 

Yeah, so I'm going to beat this to death for one more second because each time I read it I have to seriously stop, regroup, and actually think about this DC 'clamp'. You'd think I'd get this the first time and it would stick w/ me. Here, in a DC environment this DC clamp multi-meter is actually reading voltage, the multi-meter clamp creates a magnetic field (via the iron core of the clamp). "While the current flows through the wire, the clamp meter senses the magnetic field within the air gap that contains the Hall Effect detector and forces a deflection on it. The deflected silicon chip then creates a voltage perpendicular to the path of the electron flow. The clamp meter uses an internal microprocessor to convert the voltage to amps and gives the current reading."

Understanding DC Amps and the Clamp Meter

 

The article you linked to pretty much explains it. However, all this has nothing to do with what the OP is trying to do.

 

I was attempting to get to the point to determine if the alternator is actually increasing amperage as the result of turning on power consuming devices contained w/in the vehicle. Shouldn't the alternator increase its amperage output as you increase power consuming devices? Shouldn't this demonstrate the alternator is operating w/in a given range. When I read the amperage on my own vehicle, as I turn devices on & off the measured amperage varies w/in a given range relative to the power consuming devices turned on (i.e. under load). What do you think the OP is trying to do?

 

Not everyone has an inductive ammeter to read high currents (10+ Amps) but it is very easy to measure the voltage while turning on accessories to determine if the voltage stays steady (meaning the alternator current output is keeping up with demand) or if the voltage is decreasing (current output not keeping up with demand).

 

Exactly, in normal situations with minimal power consumption the volt meter will read around 14ish volts. As you turn on things like wipers, lights, heater fan, etc, the voltage will drop. The battery acts like a ballast that stores energy and assists when demand is really high.

All the op needs to know is that when the engine is running he gets 14ish volts at the battery with minimal load on the system.

 

I got confused reading through these posts. I can't imagine what the OP is doing, translating from English (I'm assuming to German).

As stated, I think you want to verify the battery is good first and foremost. I'm not sure what kind of autoparts place you have available in Innsbruck, but if you have one, they should be able to test it. If not, you can do a quick check in the car by turning IGN to RUN without starting the car, with no loads, and then adding lights, fan, radio etc, and making sure battery voltage doesn't drop below 10.5V. It should really stay well above that.

Then, I would check with engine running what the voltages are between the battery terminals (leads on the terminals, not the clamps), and then move the positive leads to the positive cable, and then over to the BAT output of your alternator. If all of these are reading 12.x V, then you should have good connections, but you aren't getting anything out of the alternator. Keep the negative lead on the battery terminal minus side. That way, you're checking ALL of the wiring and connections on the ground side of things as well. If you don't get 12.x V at the alternator terminal, you may have a wiring issue on either the positive or tne negative side, you'll just have to trace it down.

IF that is OK, with the engine off, and IGN in RUN, check the small connector going into the alternator. One of those pins needs to have battery on it or you are not going to get the alternator to charge. As Nicks66 said, it looks like those wires have been changed in the past, so that might be a key spot to check.

If these are all ok, other than you're not getting 14.x volts out, it sounds like the alternator. But, I'm suspecting you've got something else going on just based on the age of the alternator.

 

Issue solved. Don’t ask what the problem was, I will not answer....too embarrassing

Thank you for your Input and feedback