Alternator not charging?

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pcatterall

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The alternator on the 'new' boat didn't seem to be charging; no movement on the ammeter and no increase in bat voltage.
Removed alternator and had it checked, it was ok, refitted it, still no charge.
There are just 2 leads ( 1mm and .5mm red) the heavy lead comes from the alternator up to the control area and back ( directly wired through the meter) This circuit checks ok.
The ign light comes on but stays on.
The batteries are in good condition ( kept topped up with solar panels) and show around 13.1 volts.
What should I check next?
 
Ign light stays on and alternator is OK ......... ??????

Check wiring between warning light and alternator. Make sure it goes to the correct terminal on the alternator and that it is not shorting to earth somewhere.

Disconnect it from the alternator ... it should not then light at all.
 
Alternator woe

Really dumb, but is the drive belt tight and driving the alternator or is something seized? Ask yourself how I might ask this
 
How is the alternator grounded? Case or separate wire?

When electrical stuff that used to work stops, then it is 99% of the time in the connections.

Check each one.

Sounds like you have an ammeter in your cockpit engine panel. If so, all of your charging is going through what is usually a small wire, up to the ammeter, and then back to the batteries.

Consider improving that inefficient charging source if that's how your boat is wired.
 
Stu Jackson said:
How is the alternator grounded? Case or separate wire?

When electrical stuff that used to work stops, then it is 99% of the time in the connections.

Check each one.

Sounds like you have an ammeter in your cockpit engine panel. If so, all of your charging is going through what is usually a small wire, up to the ammeter, and then back to the batteries.

Consider improving that inefficient charging source if that's how your boat is wired.
Click to expand...

If the alternator was not grounded the warning light wouldn't come on at all. Worth checking for a poor connection though.

Sounds like he may have a direct reading ammeter/one with an integral shunt. Could be an automotive one.
He does say heavy lead
 
Check alternator wiring

Using a volt meter or small 12v bulb you should have 12v positive at the heavy wire at the alternator.
You should also get 12v on a meter when the engine "ignition" switch is on at the thinner wire going to the regulator. You may not get much of a glow out of a bulb used here as the power is via the "alt" lamp.
An inadvertant short to negative or earth on this wire will give a alt lamp on but no charge. This will show up as no voltage at the alternator. We assume here that the alternator has an internal regulator. If it has an external reg then there are more wires to check. good luck olewill
 
Had almost exactly the same problem last weekend. Alternator suddenly stopped charging and charge light on the panel glowing.

Turned out to be corrosion on the connector to the back of the control panel. All cleaned up and working OK now!
 
Thanks guys. Yes engine was running and belt tight enough!!
Cant get at the ammeter but think it's one with its own shunt, the beefy wire goes in and out direct from it.
I guess that if I test the 'big wire circuit' with a large bulb then this will check the ammeter itself?
Logic at this time suggests that WH and VicS may be near the mark with the suggestion about an inadvertant earth on the 'small' wire. Incidently the charge bulb doesn't come on when the ignition is switched but only after the engine is running and then , as I said, stays on until ign is switched off.
Thanks again.
 
with engine stopped check to see if battery voltage is present at the alternator+ terminal. remove the small wire and switch on the ignition and check voltage here (warning light should not come ON) if it does you have a short to earth from the light to this connection.. A further test would be to start engine and with a seperate 12 volt supply flash to the wl terminal and the alt. should energise.
 
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pampas said:
with engine stopped check to see if battery voltage is present at the alternator+ terminal. remove the small wire and switch on the ignition and check voltage here (warning light should not come ON) if it does you have a short to earth from the light to this connection.. A further test would be to start engine and with a seperate 12 volt supply flash to the wl terminal and the alt. should energise.
Click to expand...

yes battery voltage at + terminal
When small wire removed no battery light
Does the 12 volt 'flash' mean just a quick touch to the terminal or can I just clip it on.
I guess that this just bypasses the connection through the ignition but havn't I read that there must be a bulb present to creat a current draw? ( Someone wanted to use an LED but was advised that there would be insufficient draw to 'excite' the alternator)
I will check all connections at the control switch.
 
pcatterall said:
Thanks guys. Yes engine was running and belt tight enough!!
Cant get at the ammeter but think it's one with its own shunt, the beefy wire goes in and out direct from it.
I guess that if I test the 'big wire circuit' with a large bulb then this will check the ammeter itself?
Logic at this time suggests that WH and VicS may be near the mark with the suggestion about an inadvertant earth on the 'small' wire. Incidently the charge bulb doesn't come on when the ignition is switched but only after the engine is running and then , as I said, stays on until ign is switched off.
Thanks again.
Click to expand...

Snip
"Logic at this time suggests that WH and VicS may be near the mark with the suggestion about an inadvertant earth on the 'small' wire."

One simple way to prove this would be to disconnect the existing warning lamp wire at he alternator, then jury rig a warning lamp via a 5A fuse directly from the positive on the battery to this terminal. Then if the Jury rig lamp works correctly and the alternator produces charge The fault then is indeed in the key switch warning lamp alternator circuit as suggested in previous posts

Cautionary note

If the alternator becomes detached from the batteries when charging its diodes may well be damaged. So this test should not be carried out in isolation without first checking the heavy cables from the alternator to the batteries via the ammeter and the 1-2-both switch as previous posts. Also don't forget the negative/earth side as this returns the same charging current. Indeed in other similar posts its been noted that relative high resistance can occur between the alternator mountings/case and the engine block

Good luck with your investigations, I see your going to post your findings, I for one will be interested in the results.
 
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Incidently the charge bulb doesn't come on when the ignition is switched but only after the engine is running and then , as I said, stays on until ign is switched off.
Click to expand...
Only just noticed that.

Its not incidental information . its very relevant. Put a whole new complexuon on things.
It should come on as soon as you turn the switch to the normal running position.

Thinking cap on again!.
 
steve28 said:
and still be on when cranking

steve
Click to expand...

Going out once the alternator is up to speed and generating.

Puzzled a bit..
Normal current flow when just switched on but not running is from the switch via the lamp through the field coil, brushes and regulator to earth ( exact sequence depends on whether it is positive or negative regulated)

If it comes on once the engine is running, but the alternator apparently not generating what's the current flow path ... not the above or it will have come on when not running?

:confused:
 
VicS said:
Going out once the alternator is up to speed and generating.

Puzzled a bit..
Normal current flow when just switched on but not running is from the switch via the lamp through the field coil, brushes and regulator to earth ( exact sequence depends on whether it is positive or negative regulated)

If it comes on once the engine is running, but the alternator apparently not generating what's the current flow path ... not the above or it will have come on when not running?

:confused:
Click to expand...

Me too!!! maybe more than one fault?........That's why I suggested eliminating a possible fault on the warning lamp circuit
 
Yes, thanks guys. As I say this is my 'new' old boat so I don't know if this is how the boat was wired or if there is a fault which developed since I bought her.
My instinct is to follow the suggested path of 'by passing' the set up to identify the faulty circuit then work through that.
First I will have a quick look at the back of the ign switch because ( as you point out) the 'exciter' circuit should come on as soon as the ignition circuit is made.
Thanks again!! Will report back.
 
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