altenator output

[Roy10289]

I have never been very good with repair of electrical issues. Can someone advise me how I would check to see if my altenator is charging and what the output is? I keep my boat at the dock and keep shore power on to charge batteries and keep the refrigerator running. Consequently,even if my alternator was not working,I wouldn't know till too late if I stay on moorings for a few days in a row.

 

[Ross]

The best way is to install an ampmeter in the alternator to battery connection. The meter should have a full scale range greater than the alternator rating.

 

[kloudie1]

Roy, A really quick and dirty method is to use something like this http://www.amazon.com/Equus-3721-Battery-Charging-Monitor/dp/B000EVWDU0 plugged into a cigarette lighter outlet. It reads voltage so it will not give you outlet power, only voltage.. It givees a really rough idea about the system because if it reads a volt or so above battery voltage at an engine rpm of about 1000 (fridge not running) .. then it is telling you that the alternator is working and putting out some juice.. when running art cruising rpm with electric loads turned on, it should still read above battery voltage .. If it is doing that, chances are the alternator and voltage regulator is fine. They are available at auto parts stores too. Remember, this does not tell you how much it is putting out but that it is putting out something.. most alternators will not pass this simple test meter if anything is wrong.

 

[joetekno]

Here is a great site that will walk you through testing your alternator. http://www.carbasics.co.uk/How_to_test_your_alternator.htm Regards, Joe

 

[Roy10289]

Thanks kloudie1 for that link. I'll order one of those for sure. In the meantime, I do have a very cheap VOM meter. If I put the leads across the 2 termanals on the alternator will this tell me anything? I don't want to short out anything.

 

[kloudie1]

Put it across the battery terminals if you can get to them.. or the back side of the battery switch.. Main alternator outlet wire to ground is OK.. but yes, if it reads (with engine running) 13.5+ volts, probably more like 14, you are good. Joe's link gives more info on this Q&D method..

 

[Stu Jackson]

Good advice. However, before you do your test, turn off your shorepower and run your fridge for a few hours (or even overnight depending on your house bank capacity). You NEED to have a drawn down bank to have your alternator's regulator tell the alternator to produce current. If the batteries are completely full, the alternator won't need to "work."

 

[Snotter]

Clamp a clamp-on digital meter around the altenator's output wire. If you don't have a digital meter, borrow one. The meter will tell you output current.

 

[Stu Jackson]

More thoughts: kloudie's idea is fine, but you'd get more use from a digital volt meter than that unit, 'cuz you could use it in other places. Plus cig lighters are pretty flimsy devices with small wiring which could and will have high voltage drops, giving you lower readings.

You could also buy and install a Victron energy monitor. That'd tell you a LOT more about your system. $158.

 

[Benny17441]

For testing alternators I use an induction ammeter. It will give you a power reading of the current flowing through a wire without having to do any connections. Yes, make sure the batteries are partially discharged as the alternator needs to be energized.