Is it the alternator or the gauge

[Bayou Sailor]

Hi guys, My engine issues are 1000% better. Margarita runs like new and no exhaust issues. No smell, no smoke, GREAT. Now, I noticed that the ammeter not moving at all. It just sits dead in the middle. The gauge goes to +- 60 amps. How can I check to see if it is the gauge or the alternator? I looked at the electrical forum and didn't see anything. Any help?

[Al Schober]

Hopefully you have a digital voltmeter that you can trust. If not, get one.
Curious what your ammeter is supposed to read. Just alternator output, or does it measure all current in/out of your batteries. If the meter came with the boat, it's likely just alternator output. New (smarter) systems put a shunt in the negative leg to the house bank and measure current both ways. There are shunt meters that only do alternator output.
First step should be to measure the output voltage of the alternator, engine running. If it's more than battery voltage you should see charge current, hence a meter/wiring problem. If there's no/low alternator voltage you have an issue with the alternator or its regulator - don't confuse the two. Problems with either will prevent output from the alternator.

[Bayou Sailor]

Thanks Al. Quick question, my battery goes through a Perko switch. Will the voltage reading be correct at the battery?

[joe_db]

At the battery is what matters

[sastanley]

Bayou, AL's excellent post covers many scenarios. The problem is a lot of these boats now have seen multiple owners and many have changed things over the years, hence the need to figure out how your boat is wired.

If you were to measure the voltage at the battery, please take into account that ANY and ALL connections between the alternator and the battery could affect the ability to charge the battery, or limit that effectiveness. However, as Joe commented, that is the ultimate goal..make sure the alt brings up the battery when the engine is running. True battery voltage will be available at the battery posts, and should be somewhere between 12.6v and 12.8v at rest under no load. But, does it answer the question you are asking? The ammeter is likely in the middle of the circuit..your question is why does it read zero (or as I will explain later, appear to be zero?) I think the answer is at the alternator end of the circuit, not the battery end..for now. If you can get a voltmeter on the (+) output of the alternator and the (-) on a good ground on the engine (I use the alternator mounting bracket bolt, but mine is SS and not covered with paint) we can instantly tell if the alternator/regulator package is working. If it is not 13.8+ volts, one of those two is not working.
IMO, that is the first test, and then we move forward from there.

edit - to add in a few more thoughts, these older ammeters were WAY more range than ever could be put out by the 35A Motorola alternators. At first startup when you've drained the battery with the blower and the starter, you should see the gauge maybe as high as +15-20 amps for a minute or several minutes. As the battery is charged its ability to take those amps diminishes, it may be charging at 3 or 4 amps as it is being topped off, that will barely register on a -60/60+ ammeter. - There are MANY factors involved here, we are trying to figure out where your scenario falls and provide appropriate advice.

The next questions I have will be:
-What type of alternator?
-Original regulator?
-Wire gauge on alternator output?
-Does that output wire still run from the alternator to the ammeter in the cockpit?

[Bayou Sailor]

Thanks everyone for the input. This afternoon I will go to the boat and run these tests.

[Bayou Sailor]

Testing done

OK, I tested the voltage at the battery and the alternator. When I got to the boat, the bat was at 13.8. Upon start up the voltage dropped to 12.7 and never got any higher. During the 15 min run time, it dropped down to 12.4. Checking at the alt, the readings never got over bat voltage. I think the alt is shot. I also think the gauge is shot because it never even ticks. Not even when you turn the ignition on or off. I just hate the thought of spending $250 for the most basic alternator made. I would think any 1 wire alt that fits should work. I am not a cruiser, only day sailor.

[Surcouf]

If it was me, and I was confident that all my readings are OK in the boat, I would remove the alternator and bring it to Advanced Auto Parts / Pep Boys etc... they can usually test it for free.

Depending on what alternator you have, you may have just a dead voltage regulator (mounted at the back of your alternator).

One thing that must be taken into account, your alternator must/should be a "marine" one, that prevents sparks to light off potential gas fumes... not the cheapest ones... Many shops would be able to overhaul/repair your alternator for less than a new one.

[joe_db]

OK, I tested the voltage at the battery and the alternator. When I got to the boat, the bat was at 13.8. Upon start up the voltage dropped to 12.7 and never got any higher. During the 15 min run time, it dropped down to 12.4. Checking at the alt, the readings never got over bat voltage. I think the alt is shot. I also think the gauge is shot because it never even ticks. Not even when you turn the ignition on or off. I just hate the thought of spending $250 for the most basic alternator made. I would think any 1 wire alt that fits should work. I am not a cruiser, only day sailor.

If the ammeter is wired the way the standard A4 wiring is set up, it only shows alternator output. If the alternator is shot it would not move at all. The stock A4 wiring used a center-zero ammeter because they were cheap and easy to get I think, but it is not the right one for that installation. Many owners remove them and replace them with voltmeters.

Next - you do not have to spend $250 to fix this issue. First thing would be the local alternator repair shop, it might be fixable for half that.
Failing that, you can look around for used A4 alternators. People scrapping engines or replacing the stock alternator with a bigger one sometimes sell them.
You also can look for Balmar alternators that fit, but they are usually big $$$. The many variants of the 10si Delco alternators also fit with the Moyer longer alternator support arm.
The 10si form factor has been copied by all kinds of Chinese factories, you can get them for well under $100. Our host sells a 10si alternator that is many steps up from the cheapest knock-off, both in quality and price. Just make sure you get a MARINE ignition protected version, not a car version!
There is an Atomic 4 alternator on FleaBay right now

[ArtJ]

please excuse this basic question

Marine alternators need the engine throttle to be raised up a lot
for a few seconds after starting the engine. Has this been checked?

Best Art

[Bayou Sailor]

Tested

I removed the atlernator yesterday. Took it to the auto parts store. It's dead. I am going to an alternator repair shop today to see what they can do. Worse case, I'll order a new one and life goes on. Thanks again guys. Fair Winds.

[sastanley]

When you bring the alt back to the boat we need to talk about how the boat is wired. Again, as joe mentioned, the long charge circuit up to the ammeter in the cockpit is an issue. IMO connecting the alt output to the Common on the battery selector switch gives the batteries a fighting chance.
Details are important here on the Moyer forum..please follow up with us.

[joe_db]

I removed the atlernator yesterday. Took it to the auto parts store. It's dead. I am going to an alternator repair shop today to see what they can do. Worse case, I'll order a new one and life goes on. Thanks again guys. Fair Winds.

FYI - I have had my 50A Motorola repaired twice over the years and the Balmar once. The usual issue is losing diodes.

[Bayou Sailor]

Pretty good news

The alternator has external VR. The wire from the VR was taped off and not connected. Daniel, the alternator guy said the alternator is putting out but the VR and diode are fried. He also told me that the way that the alternator was connected it was never working! With the onboard charger hooked to shore power all the time, the battery never ran down. It is only about 15 minutes from the harbor to hoisting sails. He ordered me a Delco marine use alternator that he said will "bolt right up" and he ordered the VR and diode pack. I don't have a lot of faith that the delco will fit, but we'll see. It's only $100 and I don't pay until it's working. If it does, I will have the original Motorola repaired ($90) and shrink wrapped and put on a shelf in the shop. Fingers crossed.

[joe_db]

The alternator has external VR. The wire from the VR was taped off and not connected. Daniel, the alternator guy said the alternator is putting out but the VR and diode are fried. He also told me that the way that the alternator was connected it was never working! With the onboard charger hooked to shore power all the time, the battery never ran down. It is only about 15 minutes from the harbor to hoisting sails. He ordered me a Delco marine use alternator that he said will "bolt right up" and he ordered the VR and diode pack. I don't have a lot of faith that the delco will fit, but we'll see. It's only $100 and I don't pay until it's working. If it does, I will have the original Motorola repaired ($90) and shrink wrapped and put on a shelf in the shop. Fingers crossed.

A Delco is probably a 10Si. It will "bolt right up" for sure, but might need a longer support arm:

See this note from Moyer:
Please note that the correct O.E.M. alternator support arms measure 9 – 1/8” in a straight line from the center of the lower mounting bolt hole to the very top of the slot. Earlier O.E.M support arms only measure 8 ½” in this dimension and will not have adequate adjustment to properly tension 26” belts. Refer to product number OVEL_03_222 if you need to replace your support arm.