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-   -   Alternator troubleshooting (https://www.moyermarineforum.com/forums/showthread.php?t=11228)

amizerin 08-25-2019 07:37 PM

Alternator troubleshooting
 
Hello All,
I just bought the boat with Atomic 4 gas engine. I noticed that the alternator was not charging the batteries (low voltage on batteries (~12V) when the engine running, engine would stop if I turn off the batteries).
I blamed the alternator first as it looked a bit rusty so I ordered a new one. The new one did not help much when the output was connected to the ammeter with the orange wire. However, when I connect the alternator output direly to the red thick wire at the starter solenoid, the alternator starts working just fine (13.5-14V on batteries when the engine is running). So, the alternator didn't appear to be a problem.
My next thought was the ammeter. I measured voltage on the ammeter positive end and it was 12.5V which is expected since it's connected to red wire running from the battery. I measured the ammeter negative end and it was 12.5V as well meaning that the ammeter is passing the current just fine. The blower connected to the negative end of the ammeter works as well. Thus, the voltage on the orange wire connected to the ammeter is just normal 12.5V.
Then I measured voltage on the other end of the orange wire connected to alternator output and it was about 2V (engine not running). I would expect some voltage drop (1-2%) since the wire is about 8-10 feet long but not 10V.
It's my understanding that the orange wire is the problem. I checked and cleaned both connectors and it did not help.
I'm thinking to disconnected the orange wire and install a new 8 gauge wire from the alternator's output to the ammeter. Basically, I'm not changing anything, just replacing the faulty wire. I will also install a 50 amp fuse for safety.
Do you think I'm on the right track? What could cause the orange wire issue?
Thank you.

ndutton 08-25-2019 10:54 PM

I think you are on the right track to resolving this issue to the original factory installation.

amizerin 08-26-2019 09:40 AM

Thank you!

Dave Neptune 08-26-2019 10:35 AM

a, while stringing the new wire check to see if you have one of the dreaded trailer plug connectors connecting the engine wiring to the control panel. This is a notorious BAD connection on these old boats!


Dave Neptune :cool:

amizerin 08-26-2019 11:01 AM

Quote:

Originally Posted by Dave Neptune (Post 118161)
a, while stringing the new wire check to see if you have one of the dreaded trailer plug connectors connecting the engine wiring to the control panel. This is a notorious BAD connection on these old boats!


Dave Neptune :cool:

Yes, there are two trailer plug connectors and I suspect one of them is a problem (or both) but I couldn't fix it. I think easier would be to bypass them with a solid single piece wire & a fuse. I'm surprised that no fuses were installed in the factory setup for the alternator output.

amizerin 08-26-2019 11:17 AM

Quote:

Originally Posted by amizerin (Post 118163)
Yes, there are two trailer plug connectors and I suspect one of them is a problem (or both) but I couldn't fix it. I think easier would be to bypass them with a solid single piece wire & a fuse. I'm surprised that no fuses were installed in the factory setup for the alternator output.

Actually, it provably would be a good idea before running a new wire to cut out the orange wire from the the plug connectors and connect with new connectors. I doubt something had happened to the wire itself, the plug connectors most likely are causing problem.
If it did not help, I'll run a new wire.

Dave Neptune 08-26-2019 12:15 PM

A very probable "BINGO".

Dave Neptune :cool:

amizerin 09-01-2019 06:31 PM

After all I decided not to mess with the old orange wire. I disconnected it completely and run a new 8 gauge all the way from the alternator to the ammeter negative. It fixed the issue. I also added a 50 amps fuse just in case.
Ammeter seems to be working fine showing me positive amps when the engine is running. All in all, appeared to be a wiring problem.

tenders 09-02-2019 11:35 AM

> I noticed that the alternator was not charging the batteries
> (low voltage on batteries (~12V) when the engine running,
> engine would stop if I turn off the batteries).

Never turn off the battery switch when the engine is running. There is a good chance that will fry the alternator diodes. I don't turn my switch between "1," "All," and "2" either.

amizerin 09-02-2019 06:04 PM

Quote:

Originally Posted by tenders (Post 118246)
> I noticed that the alternator was not charging the batteries
> (low voltage on batteries (~12V) when the engine running,
> engine would stop if I turn off the batteries).

Never turn off the battery switch when the engine is running. There is a good chance that will fry the alternator diodes. I don't turn my switch between "1," "All," and "2" either.

Thanks. I was warned in the other thread and I won't do that again.


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