New Alternator!

[dllubin]

The voltage regulator that came with the car that when I bought it was an Elecman FIA12-1, and I got a new one after being told that it was bad. The problem is the same whether I'm using the brand new regulator or the old one.

I also feel like it is a wiring problem but the auto electric workshop I was at said that "all wiring to alternator and regulator looks good" he also said "verified correct key power, ground signal, and battery power to both alternator and regulator."

I should also clarify that I went to both an auto parts store and an auto electric workshop, with the parts store saying it was the regulator, and the workshop saying it was both.

The volts are the same both at the battery and at the alternator.

This is just a guess but could it be that the alternator is not getting excited? How would I test for that?

That is possible if the field circuit has a problem. Could be bad slip rings, brushes or the field coil itself. You could try checking the field circuit with an ohmmeter. You might want to rotate the alternator while you make the measurement to see if the reading remains consistent. If it is an open circuit or a very high resistance, you may have found the problem. The output of the alternator is a function of the field current. The voltage regulator varies the field current to maintain the proper output voltage under fluctuating loads. So, your voltage regulator could be good, but if the field circuit is bad it won't be able to regulate. If the alternator has high mileage, the brushes could be worn and causing that type of problem.

 

[Dr.Jeff]

Keep in mind, when the shop said the wires look good that does not necessarily mean they have sufficient current carrying capacity under load. Same for things like seeing good voltage at the various locations mentioned. Voltage and current are very different; you can see 12 volts but not be able to transmit enough current to do the job. One way to check for that is to measure the resistance for the cables and wire, connections, etc. But even that is best done under a load. It can get a little confusing at times. But keep at it, step by step. You might have already said, but do you have a test meter for volts, ohms, and amps ("multimeter")?
As you say, you are learning and this is actually a good way to really understand how the electrical system works. If needed you might look online for some tutorials on the components. But definitely feel free to ask any/all questions here. We really want to see you get this resolved correctly without wasting money on parts you might not need.

 

[Dr.Jeff]

Regarding your question about how the alt gets excited. The little warning light on the dash gives the alt a bit of resistance and therefore excites it to begin charging. If the light is glowing when you first start the engine, but goes out after the RPM's are raised a little, then the alt is getting excited. However other problems can affect when the warning light glows so it isn't the best indicator for the system's health. The fact that you are seeing over 12 volts says it is excited.

Does anyone know if the diodes are located in the external regulator or inside the alt on this model? It is sort of sounding like a bad diode bridge.

 

[dllubin]

Regarding your question about how the alt gets excited. The little warning light on the dash gives the alt a bit of resistance and therefore excites it to begin charging. If the light is glowing when you first start the engine, but goes out after the RPM's are raised a little, then the alt is getting excited. However other problems can affect when the warning light glows so it isn't the best indicator for the system's health. The fact that you are seeing over 12 volts says it is excited.

Does anyone know if the diodes are located in the external regulator or inside the alt on this model? It is sort of sounding like a bad diode bridge.

The diode bridge should be in the alternator as it needs to handle the full output current.

As far as excitation goes, unless the alternator has been unused for a very long time, the residual magnetism will start the excitation process.

From the last measurement results, it is hard to tell if the alternator is doing anything as the terminal voltage is same as the battery voltage.

You bring up a good point about the diode bridge. Those are often accessible and replaceable. If the field circuit measures OK, and the regulator is good, there is not much left but the diodes and the stator winding.

 

[theartur2000]

You might have already said, but do you have a test meter for volts, ohms, and amps ("multimeter")?

Yes I do have a multimeter. That's how I've been doing the tests. The only on-board diagnostics I have is that warning light.

As far as excitation goes, unless the alternator has been unused for a very long time, the residual magnetism will start the excitation process.

The problem did show up after I let the car sit over winter, some water got under the tarp and some rust was formed, and I wasn't thinking and left the battery hooked up. It might just be a really corroded wire somewhere that still barely sends power. Then again on rare occasions the alternator does actually kick in and I get charging voltage.

 

[Dr.Jeff]

on rare occasions the alternator does actually kick in and I get charging voltage

A corroded contact can do that, as vibration makes the connection through the contamination come and go. I've also seen a bad cable (the large battery cables, between the alt/starter/battery) that looked perfect from the outside, but corroded internally. It would allow power to pass at a low level most of the time. Then as the cable flexed from movement of the engine, a greater level of power could momentarily pass. As the corrosion gets worse the overall system performance drops.

Yes I do have a multimeter. That's how I've been doing the tests.

I figured as much but didn't want to assume anything.

 

[theartur2000]

I'll see if I can pick up some thicker wire tonight and try to replace the wire from the alternator to starter.

 

[Dr.Jeff]

Best to use a heavy gauge battery cable, with the heavy lug ends like a side post battery uses. You might be able to get one with the ends already attached and the right length. Or you will have to make it. This will help regardless.