Return to the home page...

Go Back   Moyer Marine Atomic 4 Community - Home of the Afourians > Discussion Topics > Electrical

Reply
 
Thread Tools Display Modes
  #1   IP: 205.215.242.140
Old 09-17-2017, 06:08 PM
NatySailor NatySailor is offline
Senior Member
 
Join Date: Aug 2015
Posts: 44
Thanks: 28
Thanked 4 Times in 4 Posts
New alternator mystery - high voltage

Can anyone explain why I'm reading 17+ V out of my new alternator (purchased from Moyer within the last two weeks)?

I'm getting this reading with a multimeter where I have the red lead on the output "B" terminal of the alternator, grounded on the engine block.

When I check the voltage at the solenoid large terminal, I get around 12.5V. My built-in (Moyer/analog) voltmeter also reads 12.5V, so does a little additional voltmeter which plugs into the cigarette lighter adapter. (To be clear: all of these reading are with the engine running).

The batteries are freshly charged, and I get the same reading with the battery switch set to battery 1 (start) or 2 (house)

I double-checked the wiring today (which was redone recently), and the only departure from the Moyer wiring diagram, is that the alternator output "B" terminal goes directly to the large terminal on the solenoid, instead of through an amp meter and the "batt" terminal on the ignition switch. (And I'm pretty sure this is what the directions on the alternator said to do if you don't have an amp meter).

The engine starts and runs great, but with this high reading I'm afraid to damage my batteries and electronics.

Can anyone explain this so I can relax?

Thanks in advance!
Dennis

P.S. I did not buy the high capacity alternator that Moyer sells, it's the $230 model, and this is an early model engine.
Reply With Quote
  #2   IP: 24.152.132.65
Old 09-17-2017, 09:45 PM
ndutton's Avatar
ndutton ndutton is offline
Afourian MVP
 
Join Date: May 2009
Location: Torrance, CA
Posts: 9,619
Thanks: 198
Thanked 2,208 Times in 1,425 Posts
Is there any chance in the past two weeks that the battery was switched off with the engine running, even for an instant?
__________________
Neil
1977 Catalina 30
San Pedro, California
prior boats 1987 Westsail 32, 1970 Catalina 22
Had my hands in a few others
Reply With Quote
  #3   IP: 137.103.82.194
Old 09-17-2017, 11:16 PM
joe_db's Avatar
joe_db joe_db is offline
Afourian MVP
 
Join Date: May 2009
Posts: 4,474
Thanks: 49
Thanked 1,026 Times in 721 Posts
Alternator - 17 volts
Battery - 12.5 volts
These two things are not connected to each other
Reply With Quote
  #4   IP: 205.215.242.140
Old 09-18-2017, 07:34 AM
NatySailor NatySailor is offline
Senior Member
 
Join Date: Aug 2015
Posts: 44
Thanks: 28
Thanked 4 Times in 4 Posts
Quote:
Originally Posted by joe_db View Post
Alternator - 17 volts
Battery - 12.5 volts
These two things are not connected to each other
Except as a way to double-check the reading coming off the meter.
Reply With Quote
  #5   IP: 205.215.242.140
Old 09-18-2017, 07:36 AM
NatySailor NatySailor is offline
Senior Member
 
Join Date: Aug 2015
Posts: 44
Thanks: 28
Thanked 4 Times in 4 Posts
Quote:
Originally Posted by ndutton View Post
Is there any chance in the past two weeks that the battery was switched off with the engine running, even for an instant?
Almost sure not. Are you asking because that could damage the alternator/voltage regulator?
Reply With Quote
  #6   IP: 24.152.132.65
Old 09-18-2017, 07:48 AM
ndutton's Avatar
ndutton ndutton is offline
Afourian MVP
 
Join Date: May 2009
Location: Torrance, CA
Posts: 9,619
Thanks: 198
Thanked 2,208 Times in 1,425 Posts
Quote:
Are you asking because that could damage the alternator/voltage regulator?
Yes. Your symptom, although not yet conclusive, is typical of damage due to a voltage spike from running without a battery connected. Can you provide either pictures or a diagram of your actual installation wiring so we can have a better look?
__________________
Neil
1977 Catalina 30
San Pedro, California
prior boats 1987 Westsail 32, 1970 Catalina 22
Had my hands in a few others
Reply With Quote
  #7   IP: 12.172.250.194
Old 09-18-2017, 08:12 PM
tenders tenders is offline
Afourian MVP
 
Join Date: May 2007
Location: Harlem YC, City Island, NY
Posts: 1,439
Thanks: 46
Thanked 259 Times in 170 Posts
Quote:
Originally Posted by NatySailor View Post
Except as a way to double-check the reading coming off the meter.
I think Joe means that your double-check has failed. You can't be showing a 4.5 volt differential between two places on the same circuit. If the batteries are reasonably fresh, 12.5 volts is a sign that the alternator isn't connecting to them. 17 volts from the alternator is ALSO sign that the batteries aren't connected to the alternator.

Bad connection from the alternator? Broken wire? Badly corroded wire from alternator?
Reply With Quote
  #8   IP: 24.152.132.65
Old 09-21-2017, 09:41 AM
ndutton's Avatar
ndutton ndutton is offline
Afourian MVP
 
Join Date: May 2009
Location: Torrance, CA
Posts: 9,619
Thanks: 198
Thanked 2,208 Times in 1,425 Posts
Hey Naty, any resolution?
__________________
Neil
1977 Catalina 30
San Pedro, California
prior boats 1987 Westsail 32, 1970 Catalina 22
Had my hands in a few others
Reply With Quote
  #9   IP: 137.200.32.6
Old 09-22-2017, 08:30 AM
joe_db's Avatar
joe_db joe_db is offline
Afourian MVP
 
Join Date: May 2009
Posts: 4,474
Thanks: 49
Thanked 1,026 Times in 721 Posts
Quote:
Originally Posted by tenders View Post
I think Joe means that your double-check has failed. You can't be showing a 4.5 volt differential between two places on the same circuit. If the batteries are reasonably fresh, 12.5 volts is a sign that the alternator isn't connecting to them. 17 volts from the alternator is ALSO sign that the batteries aren't connected to the alternator.

Bad connection from the alternator? Broken wire? Badly corroded wire from alternator?
Exactly - there is no way you can have that much differential across a reasonably intact wire. If you got a Moyer one-wire, run a nice thick wire (8 gauge or thicker) straight from the alternator to the heavy battery cable connection on the starter and then tell us what you get.
Reply With Quote
  #10   IP: 32.211.28.40
Old 09-22-2017, 09:49 AM
Al Schober's Avatar
Al Schober Al Schober is offline
Afourian MVP
 
Join Date: Jul 2009
Location: Uncasville, CT
Posts: 2,002
Thanks: 16
Thanked 578 Times in 405 Posts
In all this voltage checking, don't forget to check the other side of the circuit - the ground between the engine/alternator and battery negative. I've had strange things happen because of a) bad ground between alternator and block, and b) bad ground cable to/from engine.
Reply With Quote
The Following User Says Thank You to Al Schober For This Useful Post:
Dave Neptune (09-22-2017)
  #11   IP: 165.89.84.89
Old 05-29-2018, 10:11 AM
tmcdonagh tmcdonagh is offline
Senior Member
 
Join Date: Oct 2017
Location: Buzzards Bay
Posts: 18
Thanks: 14
Thanked 1 Time in 1 Post
Voltage reads 16+ volts

I ran into this same problem this weekend while motoring back to the mooring. My new Balmar smart gauge that was throwing code 4 (Battery voltage above acceptable level for selected battery type). My chartplotter was also displaying 16V. I was charging my house battery. As I was in a rocky inlet, I had no choice but to continue on. When I could safely stop the engine but still not at the mooring. I switched the battery selector to both, restarted the engine and continued on. At that point, the voltage was 13.5 volts. After picking up the mooring, I stopped the engine and noted the voltage drop for both batteries at 12.7 volts after resting. All connections seemed secure and no changes has been made other than connecting the Balmar. Suggestions?

Thanks,

Tom
s/v Servus
Reply With Quote
  #12   IP: 137.200.0.112
Old 05-29-2018, 11:54 AM
joe_db's Avatar
joe_db joe_db is offline
Afourian MVP
 
Join Date: May 2009
Posts: 4,474
Thanks: 49
Thanked 1,026 Times in 721 Posts
Describe your alternator and regulator setup. My regulator will do this if the sense or ground wires get loose.
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Electrical Connectors, Wire Length, and Voltage Drop RUSSELL Electrical 6 05-12-2015 01:45 PM
Low Voltage Troubleshooting Chris Simenstad Electrical 8 05-11-2015 05:23 PM
another coil thread Skywalker Electrical 20 12-12-2014 12:09 PM
Alternator regulation ndutton Electrical 30 02-04-2013 12:44 AM
Hot Coil and High Alternator Output Triton106 Electrical 53 10-02-2011 07:12 PM


All times are GMT -4. The time now is 04:56 AM.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2024, vBulletin Solutions, Inc.


Universal® is a registered trademark of Westerbeke Corporation

Copyright © 2004-2024 Moyer Marine Inc.

All Rights Reserved