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Have volts but low amps
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Author:  Pipedreams [ Tue Jun 09, 2015 6:13 pm ]
Post subject:  Have volts but low amps
On my vista 268 iam getting 14 volts out of alternator but only getting 16 amps, the battires are new and i just installed ne alternator? Any ideas
Author:  Thalasso [ Tue Jun 09, 2015 7:05 pm ]
Post subject:  Re: Have volts but low amps
The amperage output of the alternator is a function of the need to charge the battery and support the electrical needs.
Engine running the voltage should be 13.8 to 14.4 volts.
Turn everything on.
The amperage (load) will increase but voltage will be regulated at the 13.8 to 14.4 volt range.
Just because the alternator is a 40amp doesn't mean it is constantly putting out 40. You would toast your batteries
Author:  Pipedreams [ Tue Jun 09, 2015 7:40 pm ]
Post subject:  Re: Have volts but low amps
Thats what i thought but i ran batteries way low so it would just barely start the boat and i never saw the amps increase and i could kill the motor by hitting the trim???
Author:  Thalasso [ Tue Jun 09, 2015 9:12 pm ]
Post subject:  Re: Have volts but low amps
Pipedreams wrote:
Thats what i thought but i ran batteries way low so it would just barely start the boat and i never saw the amps increase and i could kill the motor by hitting the trim???


Guess it's time to take it to a alt repair shop, or return the alt.
Author:  Surface Interval [ Tue Jun 09, 2015 9:25 pm ]
Post subject:  Re: Have volts but low amps
As Thalasso said, the alternator voltage output should be in that voltage range when running at idle or faster, under most any amperage load. Some people will quote different numbers such as 13.5 to 14.5 or 13.9 to 14.6, but the concept of having 1 to 2 volts more than the 12.7 volts for a fully charged battery is what will charge a battery. Some alternators may not put out their rated voltage at idle, but will at fast idle or higher. The ammeter, if equipped, may read just alternator output (loadmeter gage goes from 0 to max amperage output), or it may read whether the battery is being recharged ( gage has "0" in the center). The loadmeter measures how many amps the alternator puts out, whether this amperage goes to the battery or to other electrical accessories. It does not directly show the state of charge of the battery, unless all accessories are turned off. In this case the loadmeter shows how much is going back to the battery. A fully charged battery causes the loadmeter to be reduced to near zero. Many ammeters have the "0" in the center. In this case a negative indication shows that the electrical is more than alternator output and power is being taken from the battery. A positive indication shows that the battery is being charged. This type of meter will not show total alternator output. Voltage should be relatively constant. Amperage will vary depending on electrical load and the battery's state of charge.
Author:  Pipedreams [ Wed Jun 10, 2015 5:51 am ]
Post subject:  Re: Have volts but low amps
Does any one now what the wiring should look like on back of alt.?
Colors and locations?
Author:  Paul I. [ Wed Jun 10, 2015 8:23 am ]
Post subject:  Re: Have volts but low amps
Surface Interval wrote:
As Thalasso said, the alternator voltage output should be in that voltage range when running at idle or faster, under most any amperage load. Some people will quote different numbers such as 13.5 to 14.5 or 13.9 to 14.6, but the concept of having 1 to 2 volts more than the 12.7 volts for a fully charged battery is what will charge a battery. Some alternators may not put out their rated voltage at idle, but will at fast idle or higher. The ammeter, if equipped, may read just alternator output (loadmeter gage goes from 0 to max amperage output), or it may read whether the battery is being recharged ( gage has "0" in the center). The loadmeter measures how many amps the alternator puts out, whether this amperage goes to the battery or to other electrical accessories. It does not directly show the state of charge of the battery, unless all accessories are turned off. In this case the loadmeter shows how much is going back to the battery. A fully charged battery causes the loadmeter to be reduced to near zero. Many ammeters have the "0" in the center. In this case a negative indication shows that the electrical is more than alternator output and power is being taken from the battery. A positive indication shows that the battery is being charged. This type of meter will not show total alternator output. Voltage should be relatively constant. Amperage will vary depending on electrical load and the battery's state of charge.


GREAT posting!!

I like to do basics first. Check and clean all the connections you can.
Author:  rpengr [ Wed Jun 10, 2015 9:00 am ]
Post subject:  Re: Have volts but low amps
Pipedreams wrote:
Thats what i thought but i ran batteries way low so it would just barely start the boat and i never saw the amps increase and i could kill the motor by hitting the trim???

This sounds like an issue with the battery (or battery connection), not the alternator. As long as you are getting that approx. 14 volts, then the battery should be charging.

If the alternator was not outputting sufficient amps to meet the demand (including what the battery will accept for charging), then the voltage would no longer read 14 volts. It's not possible. So it sounds like the battery is not accepting the charge.

Trim motor trying to kill the engine is often a symptom of a bad battery or ground connection, not the alternator.
Author:  noexcuses [ Wed Jun 10, 2015 9:24 am ]
Post subject:  Re: Have volts but low amps
Did you have charging problems before you replaced the batteries and alternator? Do you have a battery isolator?
Author:  Pipedreams [ Wed Jun 10, 2015 10:16 am ]
Post subject:  Re: Have volts but low amps
I had both batteries check by an interstate battery dealer they're both under-year-old and checked out good and yes I do have isolators one for each battery
Author:  Paul I. [ Wed Jun 10, 2015 1:46 pm ]
Post subject:  Re: Have volts but low amps
Pipedreams wrote:
I had both batteries check by an interstate battery dealer they're both under-year-old and checked out good and yes I do have isolators one for each battery


Remeber too; Most but not all isolators have a .6 voltage drop. So the batteriers never get fully charged.

Now you mentioned "isolators one for each battery". You should only have one isolator, could you be looking at something else?
Author:  LouC [ Wed Jun 10, 2015 3:24 pm ]
Post subject:  Re: Have volts but low amps
Go back and check all your terminals including those on the back of the battery switch and the engine grounds. If the terminals at the battery uses wingnuts, get rid of them and use bolted on (with lock washers) automotive style clamps that are marine quality. That will make a more secure connection between the battery and the bat switch and starter.
Next, if your battery was really fully charged and there was no load on it, the alt should not put out a lot of amps, and the fact that it was reading 16 amps shows that it was either not fully charged at all, or there was a big load on it when you tested, or something is not right in the wiring (alt not sensing when the batt is fully charged).
On the back of the alt there will be one thick wire (Alt output B+), and usually 2 smaller wires; one labeled E for 'excite' and one labeled 'S' for sense. It is the S terminal that should read battery voltage. How is yours hooked up?
Author:  Pipedreams [ Wed Jun 10, 2015 7:47 pm ]
Post subject:  Re: Have volts but low amps
Thanks for all the help,think i found it,the orange wire that connects to the alternator in 2 spots had a broken ring termanal on one connection never noticed this before. It was only hooked up with the light gauge jumper wire.
Author:  LouC [ Wed Jun 10, 2015 9:58 pm ]
Post subject:  Re: Have volts but low amps
On some alternators the way it's hooked up is that the heavy gauge wire goes from the alt B+ terminal to the starter solenoid. The S for sense wire may connect right to the B+ terminal as well. Take a look at the engine wiring harness diagram for your model to be sure. Some OMCs like mine had remote voltage sensing where the sense terminal was connected to a wire in the ignition harness and that sensed batt voltage in the wire. The problem with this is when resistance builds up in the circuit over the years it reads low (sometimes by as much as 2 volts ) and this fools the
Regulator into over charging the batts. The solution for these is to disconnect that sense wire from the alt and tape it up in the harness. Then make up a 14 gauge jumper wire from the sense terminal to the B+ terminal . I did this when I replaced the alt this spring and it cured my over charging problem; now it's steady at 14.3 volts, I got this info from Arco Marine. Not sure if this applies to yours but some Volvos built during the joint venture with OMC were wired like OMCs....
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