Reply
 
Thread Tools Search this Thread Display Modes
 
Old 06-17-2012, 08:10 PM   #1
Veteran Member
 
Join Date: Dec 2011
Posts: 57
Low volt reading

Hi Folks-
My voltmeter has gone from reading around 14v to just above 12v.
Batteries charged off of shore power charger are at 13+ volts.
I can get a reading of 14.25 volts off the alternator when boat is running.
Voltmeter reads below zero when key is off. It reads high 12v's when key is turned on and then drops to just above 12v when running.
What should I be looking at?
Thanks-
Eeber
Eeber is offline   Reply With Quote
Old 06-17-2012, 08:31 PM   #2
Guru
 
Moonstruck's Avatar
 
City: Hailing Port: Charleston, SC
Vessel Name: Moonstruck
Vessel Model: Sabre 42 Hardtop Express
Join Date: Nov 2008
Posts: 8,276
Quote:
Originally Posted by Eeber View Post
Hi Folks-
My voltmeter has gone from reading around 14v to just above 12v.
Batteries charged off of shore power charger are at 13+ volts.
I can get a reading of 14.25 volts off the alternator when boat is running.
Voltmeter reads below zero when key is off. It reads high 12v's when key is turned on and then drops to just above 12v when running.
What should I be looking at?
Thanks-
Eeber
Check the circuit breaker between the alternator and the batteries. Also, check your ground connections.
__________________
Don on Moonstruck
Sabre 42 Hardtop Express
When cruising life is simpler, but on a grander scale (author unknown)
https://moonstruckblog.wordpress.com/
Moonstruck is offline   Reply With Quote
Old 06-17-2012, 09:54 PM   #3
Moderator Emeritus
 
ksanders's Avatar
 
City: SEWARD ALASKA
Vessel Name: DOS PECES
Vessel Model: BAYLINER 4788
Join Date: Feb 2011
Posts: 6,267
Read the voltage on the terminals right on the back of the voltmeter.

If that voltage is actually low, trace the wires back towards the battery untill you get the same voltage as your battery.
ksanders is offline   Reply With Quote
Old 06-18-2012, 05:28 AM   #4
Guru
 
psneeld's Avatar
 
City: Ft Pierce
Vessel Name: Sold
Vessel Model: Was an Albin/PSN 40
Join Date: Oct 2011
Posts: 28,149
Quote:
Originally Posted by ksanders View Post
Read the voltage on the terminals right on the back of the voltmeter.

If that voltage is actually low, trace the wires back towards the battery untill you get the same voltage as your battery.
good troubleshooting proceedure..
psneeld is offline   Reply With Quote
Old 06-18-2012, 06:15 AM   #5
Veteran Member
 
Join Date: Dec 2011
Posts: 57
Thanks.
I'm looking at the schematic and power runs from the alternator, through the battery isolator, to the batteries, then to the battery switch and the voltmeter.
Looks like I should be reading 14.25 at the batteries when running?
I'm not.
I ran the water pressure pump and then with the engine running, I watched one battery slowly come up; 12.74, 12.75, 12.76, etc..
Thanks-
Eeber
Eeber is offline   Reply With Quote
Old 06-18-2012, 07:26 AM   #6
Guru
 
rwidman's Avatar
 
City: North Charleston, SC
Join Date: Sep 2010
Posts: 4,870
Quote:
Originally Posted by ksanders View Post
Read the voltage on the terminals right on the back of the voltmeter..
That is the obvious first test, especially if the boat's volt meter reads "below zero" with the key switch turned off.

If a "known good" meter reads one voltage when attached to the terminals on the back of the boat's volt meter and the boat's meter shows something else, the boat's volt meter is inaccurate. Boat (and car) volt meters are usually not very accurate to start with.
rwidman is offline   Reply With Quote
Old 06-18-2012, 09:27 AM   #7
Guru
 
Moonstruck's Avatar
 
City: Hailing Port: Charleston, SC
Vessel Name: Moonstruck
Vessel Model: Sabre 42 Hardtop Express
Join Date: Nov 2008
Posts: 8,276
It still sounds to me as if the problem is between the alternator and the batteries. If the alternator is putting out 14.25 volts, and the gauge is reading battery voltage, the alternator voltage is not getting to the batteries. Check for a tripped circuit breaker or blown fuse between the alternator and batteries. If that is not it, it could be a broken wire or connection. Rig a temporary wire from the alternator to the batteries, and check the gauge reading.

If there is a fuse in the circuit from the alternator to the batteries, (and it is not blown) pull the fuse and clean all contacts with emery cloth or wire brush. You may have to disassemble the fuse holder to do this. Then replace and check. It only takes a small amount of oxidation to break a circuit or reduce the voltage going through.

In the past, I have also had some bad ground connections behind the instrument panel that have caused some bad readings.
__________________
Don on Moonstruck
Sabre 42 Hardtop Express
When cruising life is simpler, but on a grander scale (author unknown)
https://moonstruckblog.wordpress.com/
Moonstruck is offline   Reply With Quote
Old 06-18-2012, 10:57 AM   #8
Guru
 
rwidman's Avatar
 
City: North Charleston, SC
Join Date: Sep 2010
Posts: 4,870
Quote:
Originally Posted by Eeber View Post
Thanks.
I'm looking at the schematic and power runs from the alternator, through the battery isolator, to the batteries, then to the battery switch and the voltmeter.
Looks like I should be reading 14.25 at the batteries when running?
I'm not.
I ran the water pressure pump and then with the engine running, I watched one battery slowly come up; 12.74, 12.75, 12.76, etc..
Thanks-
Eeber
If you have a battery isolator (not a combiner), you can expect a voltage drop through the isolator of about .7 volt because of the loss through the diode(s).
rwidman is offline   Reply With Quote
Old 06-18-2012, 08:11 PM   #9
Veteran Member
 
Join Date: Dec 2011
Posts: 57
Issue resolved.

I cleaned up the connectors on the alternator and that did the trick.
Thanks for the ideas. It helps me get my head around what I'm dealing with.

Does anyone use any gunk to keep connectors more healthy?

Thanks Everyone -
Eeber
Eeber is offline   Reply With Quote
Old 06-18-2012, 08:27 PM   #10
Enigma
 
RT Firefly's Avatar
 
City: Slicker?
Join Date: Oct 2007
Posts: 16,566
Greetings,
How about something like:
Crc Chemicals 06026 Coating No Corrode 12 Oz
There was another product and I can't remember the name (it might easily have been the same stuff) that was in non aerosol form. Ah, just remembered this:
Corrosion Block - Corrosion Control and Inhibitor products Seems I got a small sample bottle at one of the boat shows....
Hope this helps...
__________________
RTF
RT Firefly is offline   Reply With Quote
Old 06-18-2012, 08:55 PM   #11
Veteran Member
 
Join Date: Dec 2011
Posts: 57
That CRC stuff looks perfect. Great reviews.
Thanks a bunch RT.

Sincerely-
Eeber
Eeber is offline   Reply With Quote
Old 06-18-2012, 09:34 PM   #12
Master and Commander
 
markpierce's Avatar
 
City: Vallejo CA
Vessel Name: Carquinez Coot
Vessel Model: penultimate Seahorse Marine Coot hull #6
Join Date: Sep 2010
Posts: 12,559
Electricityy confounds/bewilders me.
__________________
Kar-KEEN-ez Koot
markpierce is offline   Reply With Quote
Old 06-19-2012, 05:02 AM   #13
Enigma
 
RT Firefly's Avatar
 
City: Slicker?
Join Date: Oct 2007
Posts: 16,566
Greetings,
Hold on now Mr. Eeber. Maybe I was too fast in suggesting. The CRC stuff says not for use on plastics or rubber AND it's an aerosol which sprays everywhere. Maybe not the best stuff for electrical use. Sorry about that. Next time I'll read the labels first. Suggest you go through the Corrosion block site to see if there is the same disclaimer.....Again, mea culpa
__________________
RTF
RT Firefly is offline   Reply With Quote
Old 06-19-2012, 05:34 AM   #14
Guru
 
psneeld's Avatar
 
City: Ft Pierce
Vessel Name: Sold
Vessel Model: Was an Albin/PSN 40
Join Date: Oct 2011
Posts: 28,149
Quote:
Originally Posted by RT Firefly View Post
Greetings,
Hold on now Mr. Eeber. Maybe I was too fast in suggesting. The CRC stuff says not for use on plastics or rubber AND it's an aerosol which sprays everywhere. Maybe not the best stuff for electrical use. Sorry about that. Next time I'll read the labels first. Suggest you go through the Corrosion block site to see if there is the same disclaimer.....Again, mea culpa
Can't remember if that's the waxy brown stuff...if it is ...it's great stuff for connentions in the bilge. Some boat manufacturers spray it on everything...like the new Sea Rays. It may not be ok for natural rubber and some plastics...but never saw it affect anything around normal electrical terminations...my have to use it sparingly around fuse/cb blocks.

When in doubt...spray it into the cap and use a q-tip to cover terminals in sensitive areas...it is a very good terminal/general sealer.
psneeld is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


» Trawler Port Captains
Port Captains are TF volunteers who can serve as local guides or assist with local arrangements and information. Search below to locate Port Captains near your destination. To learn more about this program read here: TF Port Captain Program





All times are GMT -5. The time now is 02:34 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012