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-   -   alternater (http://www.trawlerforum.com/forums/s4/alternater-25566.html)

castellah22 04-08-2016 05:46 AM

alternater
 
My alternator on my Grand Banks ,fitted with a Sabre 90 lehman is not charging. Theres talk of a mega fuse fitted, has anybody got any ideas
what may be wrong with it. Many Thanks. David.

Shoalwaters 04-08-2016 06:51 AM

Quote:

Originally Posted by castellah22 (Post 431493)
My alternator on my Grand Banks ,fitted with a Sabre 90 lehman is not charging. Theres talk of a mega fuse fitted, has anybody got any ideas
what may be wrong with it. Many Thanks. David.

What leads you to the conclusion that your alternator has stopped charging?

Your alt probably has two leads going to it: (i) a heavy one which carries the charge current. Probably goes to the starter motor and thence to the battery. (ii) A pair of smaller wires which plug into the back of the alt. One of these provides the current to make the alt work. Start by checking that the big wire is clean and tight at both ends. If there is a fuse, this is where it will probably be. Check that the plug on the little wire fits firmly in the alt. Check that there is 12 volts between one of the little wires and ground when the ignition switch is on and before starting the engine.

OK experts, over to you.!

High Wire 04-08-2016 07:40 AM

Using a digital voltmeter, does the battery voltage rise at all above the pre-start voltage?
-Check the wiring as Mike said above. If you have a ammeter on the dash, the power out of the alternator goes all the way up to the dash and back to the engine. Lots of opportunity for a bad connections.
-Check the belt tension and condition. Slipping belts won't drive the alt to charge more than a couple amps but the voltage will rise a few tenths.
-Sometimes the alt or the internal voltage regulator just goes bad. A stock alt is cheap and easy to replace.

RT Firefly 04-08-2016 07:57 AM

Greetings,
Mr. 22. I have no idea what the situation is across the pond but in NA most auto supply places have the facility to test alternators and starting motors, sometimes free. Unless you find the problem by following the above suggested steps you'll be taking it off anyway so...

Larry M 04-08-2016 08:02 AM

If you have or can get a copy of Boatowner's Mechanical & Electrical Manual: How to Maintain, Repair, and Improve Your Boat's Essential Systems by Nigel Calders. It has a good trouble shooting guide.

Alaskan Sea-Duction 04-08-2016 11:27 AM

Not sure if you have a parts place that will test it for you. Disconnect your battery, remove and let the shop test it. Good luck! Go Arsenal!!!!

Bacchus 04-08-2016 01:44 PM

Some Alts also have a ground wire vs a case ground - may be marked (E)
BE sure to check it as well as the others mentioned.

If you find a shop to test it they can confirm it is working and let you know what the output V is as well as the RPM that it "kicks in" and begins to charge.

A clamp on DC amp meter easiest way to confirm output and worth having for other troubleshooting aboard.
There are some reasonable $ ones out there - just be sure to check if it does DC as well as AC - some are AC Amp only

Shoalwaters 04-08-2016 03:04 PM

1 Attachment(s)
Quote:

Originally Posted by Bacchus (Post 431630)
. . . . A clamp on DC amp meter easiest way to confirm output and worth having for other troubleshooting aboard.
There are some reasonable $ ones out there - just be sure to check if it does DC as well as AC - some are AC Amp only

Agreed - excellent investment. Clamp it around the positive or negative charging cable and it tells you what's going on inside. Mine was around $145 from Amazon earlier this year. Klein make really nice stuff too. It is reading 5.2 amps in the pic below.

kchace 04-08-2016 08:11 PM

I have the same meter and use it often. Excellent meter.

Ken

Bacchus 04-08-2016 08:34 PM

Quote:

Originally Posted by Shoalwaters (Post 431657)

Agreed - excellent investment..... Mine was around $145 from Amazon .

Sears has for about 1/3 of that+\-.
Satisfies most basic troubleshooting needs

castellah22 04-09-2016 04:29 AM

Thanks everyone for all your advice, will let you know if it cures it. Thanks again.
David.

JDCAVE 04-09-2016 10:49 AM

Shoal: that's a spanky, shiny engine!


Jim
Sent from my iPad using Trawler Forum

Shoalwaters 04-11-2016 06:16 AM

Thanks Jim, polished every day!

bayview 04-11-2016 07:35 AM

Measuring current is not veryinformative as it can be near zero when everything is working properly. Measure the voltage chnge as posted above. A cheap difital multimeter ($5 US) is all ypu really need. The expensive meter is nice but only if it also has a frequency meter. Then you have the whole works.


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