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  #1   IP: 142.167.153.154
Old 08-25-2019, 07:37 PM
amizerin amizerin is offline
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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.

Last edited by amizerin; 08-25-2019 at 08:58 PM.
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  #2   IP: 24.152.132.140
Old 08-25-2019, 10:54 PM
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ndutton ndutton is offline
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I think you are on the right track to resolving this issue to the original factory installation.
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1977 Catalina 30
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prior boats 1987 Westsail 32, 1970 Catalina 22
Had my hands in a few others
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  #3   IP: 142.167.153.154
Old 08-26-2019, 09:40 AM
amizerin amizerin is offline
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Thank you!
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  #4   IP: 97.93.70.7
Old 08-26-2019, 10:35 AM
Dave Neptune Dave Neptune is online now
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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
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  #5   IP: 142.167.153.154
Old 08-26-2019, 11:01 AM
amizerin amizerin is offline
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Quote:
Originally Posted by Dave Neptune View Post
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
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.

Last edited by amizerin; 08-26-2019 at 11:05 AM.
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  #6   IP: 142.167.153.154
Old 08-26-2019, 11:17 AM
amizerin amizerin is offline
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Quote:
Originally Posted by amizerin View Post
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.

Last edited by amizerin; 08-26-2019 at 11:23 AM.
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  #7   IP: 97.93.70.7
Old 08-26-2019, 12:15 PM
Dave Neptune Dave Neptune is online now
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A very probable "BINGO".

Dave Neptune
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  #8   IP: 142.167.153.154
Old 09-01-2019, 06:31 PM
amizerin amizerin is offline
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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.
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  #9   IP: 72.69.36.126
Old 09-02-2019, 11:35 AM
tenders tenders is online now
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> 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.
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  #10   IP: 142.167.153.154
Old 09-02-2019, 06:04 PM
amizerin amizerin is offline
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Quote:
Originally Posted by tenders View Post
> 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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