Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 10-07-2017, 10:51   #1
Registered User

Join Date: Jan 2016
Location: Maine
Posts: 68
Testing Alternator Procedure

I'm not convinced my alternator is charging my battery bank. Or, at least I'd like to verify it is before we cruise. My kids DID switch the battery switches on and off when the engine was running recently. I know that can be a bad thing. How can I test that the alternator is supplying charge to my battery bank?
__________________

CourageousME is offline   Reply With Quote
Old 10-07-2017, 11:09   #2
Registered User

Join Date: Feb 2013
Location: Lago de Izabal, Guatemala
Boat: Seafarer36c
Posts: 4,599
Re: Testing Alternator Procedure

You need a volt meter.
__________________

Ecos is offline   Reply With Quote
Old 10-07-2017, 11:11   #3
Registered User

Join Date: Jan 2016
Location: Maine
Posts: 68
Re: Testing Alternator Procedure

I own one
CourageousME is offline   Reply With Quote
Old 10-07-2017, 11:12   #4
Registered User

Join Date: Jan 2016
Location: Maine
Posts: 68
Re: Testing Alternator Procedure

What's the process or procedure?
CourageousME is offline   Reply With Quote
Old 10-07-2017, 11:14   #5
֍֎֍֎֍֎֍֎֍֎

Cruisers Forum Supporter

Join Date: Apr 2006
Posts: 14,158
Re: Testing Alternator Procedure

IF there's no voltmeter or other instruments on board?

Buy a $20 multimeter at a big box store. (Not the hardware chains, they tend to double the price.) Check battery voltage when the engine is off, check it again when the engine is on. If the alternator is working, it should be 13.8-14.4 VDC when running. Anything less, especially under 12.8, indicates you are just running on batteries and the alternator is damaged.
hellosailor is offline   Reply With Quote
Old 11-07-2017, 02:43   #6
Senior Cruiser
 
GordMay's Avatar

Cruisers Forum Supporter

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 32,473
Images: 240
Re: Testing Alternator Procedure

GENERAL INSPECTION:

A loose drive belt can cause slipping and undercharging, noise and vibration, and premature belt wear. An over-tight belt may cause bearing wear.

Look at and feel the drive-belt, examining for cracking, fraying, glazing, and/or separation. Replace damaged belt(s).

Test the belt tension by firmly depressing midway between the sheaves. The belt should deflect between 1/4" (for sheaves with 7" - 10" centerline separations) and " for 12" - 16"separations). Adjust tension as necessary.

Inspect all wiring and terminations. Wire should be adequately sized for the application (see “Ohm’s Law & Boats”), secured at least every 18", and run as high and dry as possible. Termination s must be clean (no visible corrosion), and tight. Examine the wire for thermal (melting or charred insulation) or mechanical damage (frayed, cracked, or missing insulation).
Replace damaged or undersized wire, and replace or repair inadequate terminations.

ALTERNATOR VOLTAGE TESTS:

1. Set Voltmeter to DC Volts (20V scale), and connect the DC Voltmeter test leads to the battery post (Red lead to Positive Post, and Black(or Yellow) to Negative). With engine “off”, read and note battery voltage (see “Battery Testing”).

2. Start the engine, and at “Idle” RPM, check the voltmeter reading. At very low speeds the alternator output may be lower than the regulator setting; hence you will expect to read the battery voltage.

3. Increase engine RPM, and note increasing voltage reading to a maximum of about 14.2 volts (12V Nominal System - expect 29.5V in 24V system).

If no voltage increase noted, you likely have a bad voltage regulator, or poor wiring
(Alt’ to Batt.). Go on to test 3B.

If Voltage increases go on to test 4.

3B. With engine “off”, connect Positive test lead to Alternator Output (“B+”, or “A”), and Negative Lead to the Negative Ground Post (“Neg”, or “E”) of Alternator. Start engine. If Voltage increases with increased RPM, your regulator is OK, and the problem is in the wiring. Go on to test 3C.

3C. Discharge the Battery to less than 12.5 Volts. Check for Voltage drop between the Alternator and Battery, as follows..
Connect the Positive Test Lead to the Alternator Positive Output Terminal (B+) and the Negative Lead to the Positive Battery Post. Crank the engine, and increase RPM to a fast idle. Observe Voltage. If the voltage climbs to as much as 0.02 Volts (or more), the positive cable has a high resistance. Repair or replace cable.

Check for voltage drop in the negative cable, as above - but: connect the Positive Lead to the Alternator’s Negative Output Terminal, and the Negative Lead to the Negative Battery Post. Analyze as above.

From Post 1 ➥ BASIC Alternator Testing
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"



GordMay is online now   Reply With Quote
Old 11-07-2017, 04:33   #7
Senior Cruiser
 
GordMay's Avatar

Cruisers Forum Supporter

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 32,473
Images: 240
Re: Testing Alternator Procedure

See also ➥ Basic Alternator Test - Page 1 of 2 - Goto page 2: http://cruisersforum.com/photopost/showphoto.php?photo=1694 Cruisers & Sailing Photo Gallery

And ➥ Basic Alternator Test - Page 2 - Goto page 1: http://cruisersforum.com/photopost/showphoto.php?photo=1695 Cruisers & Sailing Photo Gallery
__________________

__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"



GordMay is online now   Reply With Quote
Reply

Tags
alternator

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Testing an alternator landonshaw Electrical: Batteries, Generators & Solar 2 25-01-2015 07:19
Testing for isolated alternator? heintje23 Electrical: Batteries, Generators & Solar 6 18-05-2014 10:31
Load Testing and Conductance Testing Joe500 Electrical: Batteries, Generators & Solar 0 02-12-2009 15:12
BASIC Alternator Testing GordMay Construction, Maintenance & Refit 9 01-09-2003 02:03



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 06:42.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2018, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.