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bad alternator? |
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bsucics 
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Joined: July-18-2006 Location: United States Status: Offline Points: 109 |
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 Topic: bad alternator?Posted: August-30-2008 at 3:22pm |
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Need a little advice...boat died with no warning last time it was used. The battery was 2 1/2 years old so we went ahead and replaced it - were back in business. However the voltage warning light always stayed on, the gage read 11v running, and 10 with the blower on. I picked up a meter this weekend - I read 12.39v from the battery when off, 12.15v from the battery when on/idle and 1.2v from the back of the alternator (assuming this should be around 13?). Not really sure what I'm doing here or even if I'm taking the correct raedings...but this doesn't seem right. Thanks in advance for the help.
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PaCemkr86
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Joined: August-27-2008 Location: United States Status: Offline Points: 43 |
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Posted: August-30-2008 at 3:26pm |
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If your wiring to your battery and alternator is good, it looks like the alternator isn't charging.
Id remove the alternator and run into auto zone or something and have them bench test it for you. |
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Phil Underwood
1976 Ski Tique |
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bsucics
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Posted: August-30-2008 at 5:16pm |
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Thanks - I'll plan on doing that. Can I expect to get through the weekend or am I asking for trouble?
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74SkiNautique
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Joined: July-29-2008 Location: Lynchburg, VA Status: Offline Points: 228 |
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Posted: August-30-2008 at 9:45pm |
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If the altinator isn't charging, the engine will only run for so long b4 the battery goes dead.
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74SkiNautique
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PaCemkr86
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Posted: August-30-2008 at 11:42pm |
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take a spare battery with you.. Or
it shouldn't be that much trouble to pull the alternator off in the auto zone parking lot, have them check it, and install the new one before you head out. |
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Phil Underwood
1976 Ski Tique |
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kevin719
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Joined: June-18-2008 Location: United States Status: Offline Points: 231 |
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Posted: August-31-2008 at 12:12am |
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I am not sure if auto zone has them but napa does.It is a full system tester from midtronics.All you need to do is hook to the battery and start. What about your volt. reg.??
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kevinindy
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nuttyskier2002
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Posted: August-31-2008 at 5:44am |
Something's not right with your readings. Regardless of what your alternator puts out, you should read the same voltage at the alt. B+ terminal as you read across the battery (unless you have a wiring issue). What's in the circuit between the Batt and Alt. B+? Circuit breaker? Is it tripped? Do you have a burnt wire? |
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95 Malibu Echelon w/Mercruiser 350 Magnum Skier
Former boats: 88 Ski Centurion Tru Trac II 59 Chris Craft Capri (woody) |
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bsucics
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Posted: August-31-2008 at 4:53pm |
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Unfortunately - this is close to where I reach the limits of my expetise (or lack thereof) - I'll trace the wiring and do a better visual inspection and check the reading again. I'll pull the alt. out tomorrow to get it checked.
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bsucics
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Posted: August-31-2008 at 5:33pm |
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Sorry - stand corrected. I got a better look at what I was doing... Not surprisingly, reading off of the 'correct' positive term with the other lead grounded gave me 12v. Does that mean my alt. is ok and I have a different issue that is giving me the low voltage on the gage w/warning light? Thanks!
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nuttyskier2002
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Posted: August-31-2008 at 6:41pm |
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Okay, that sounds better. Not saying your alternator is good,..... you need to get that checked as it is suspect. But it is good that you are reading the same voltage on the alt and batt. Now here's a question for you. What year is your boat? Exteranl regulator or no?. If the regulator is internal, I'd say the alternator is bad. But pull it and get it checked anyway. Replace only with marine unit. Hope this helps. Brian
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95 Malibu Echelon w/Mercruiser 350 Magnum Skier
Former boats: 88 Ski Centurion Tru Trac II 59 Chris Craft Capri (woody) |
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bsucics
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Posted: August-31-2008 at 7:05pm |
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Thanks. It's an 89, so I'm pretty sure regulator is internal - correct?
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PaCemkr86
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Posted: August-31-2008 at 9:55pm |
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internal
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Phil Underwood
1976 Ski Tique |
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nuttyskier2002
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Posted: August-31-2008 at 11:09pm |
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Yep, 89 would be internal, so its more than likely the alternator.
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95 Malibu Echelon w/Mercruiser 350 Magnum Skier
Former boats: 88 Ski Centurion Tru Trac II 59 Chris Craft Capri (woody) |
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lewy2001
Grand Poobah 
Joined: March-19-2008 Location: NSW Australia Status: Offline Points: 2234 |
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Posted: September-01-2008 at 5:20am |
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You can test your alternator in the boat by doing the following procedure.
Measure the battery voltage without engine running should be around 12.5 V if battery is in good condition and charged. Now star the engine & measure voltage again it should be higher i.e 12.75-13.75 if it is charging from alternator. If it does not go higher with engine running at idle increase revs to around 2500rpm and see if the voltage increases now. If the voltage increases with engine running to approx the stated values the alternator is good. If the battery is low to start with less than 12V the charging voltage may even go higher than 13.75 so it is more obvious the alternator is working. If there is no increase in voltage the alternator is not charging. |
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bsucics wrote: