I have had no problem with charging the batteries until today. Normally 3 to 4 hours of cruising shows the batteries at 100%. ( I know don't trust battery monitors but my batteries are 6 years old and still happy) 

Today the batteries are still at 94% after 3 hours. 

The monitor shows no charge is coming off the alternator , it usually shows around 50 amps. 

Also the alternator normally kicks in after about 10 seconds. It makes a high pitched noise and the engine revs drop slghtly. This is not happening. 

Both belts on the alternator are tight and seem to be turning fine. 

I'm running the on board genny at the moment and its charging the batteries as normal. 

Any idea's please. 

Edited August 21, 20242 yr by Felshampo

How old or how many hours has the alternator done because it may be worn brushes - if Leece Nevile uses them. I am not sure about that because I have never worked on one. Google suggests it does.

 

It also seems that it is a 6 diode machine so the warning lamp is not much use for diagnosis. Be very wary, it seems they use B+ to signify the warning lamp connection. On no account connect that to the battery.

 

This link may help https://www.peivinlookup.com/Category/8LHA2070VB/PRESTOLITE-LEECE-NEVILLE-8LHA-12V-160A-BRUSH-ALTERNATOR

Cheers Tony.

 

I think it might be this one, which is brushless. 

 

https://smithcoelectric.com/products/blp2303gh-new-oe-leece-neville-alternator-for-ihc-12v-140a

Does the alternator have a warning light? It doesn't look as though it does from the connections, but worth asking! Depending on the exact model, the alternator may use power coming down the warning light circuit as an indication to "wake up" so if the bulb had blown this could be the problem. It would help to know the exact model of alternator as there are a number of similar variants.

 

If it doesn't have a warning light, there is not much left to check except that I would check it is still connected to the batteries ie if there is battery voltage across the big red and black terminals on the back of it. Otherwise I think you will have to remove it to be checked. As Tony says, one possibility is worn brushes but could be something else. There is a procedure for restoring the residual magnetism in the rotor (necessary for it to start, being a 6 diode machine without IG terminal) but it seems unlikely that this has been lost unless there was some "event" such as mechanical shock or reverse connection.

No lights on the alternator. As far as I know. The only reference on it is the little sticker. 

Its got power coming in from the batteries, I just checked. 

If its the one I think it is its brushless. 

Looks like I need to visit an electrician then. 

Leece Neville ( Prestolite ) have their own travelling service engineers, a phone call to them may answer your problem directly.

I have found them to be excellent at solving these problems speedily.

 

I am a bit concerned that normally it makes a noise before it starts charging. Unless this is only belt slipping squeal I would worry about a mechanical failure or the alternator. It should not make any noise.

Its always done this. I will need to see what the engineer says. I'll try phoning them in the morning. 

My beloved Prestolite AV28 died last year. Regrettably parts are no longer available. I hope you have better luck. 

It could be suffering from Brasso ingestion of course.