Another alternator question (faulty or not).

[Bugsworth Tippler]

The 90amp alternator fitted to my Isuzu 35 engine (the one charging the starter battery) was recently replaced by RCR. So far I have been unable to ascertain its maker or model but it looks substantial (and very black).

 

On a test journey I continually monitored the starter battery and the services battery bank using the fitted BMV712 Battery Monitor and mobile phone app.

 

The new alternator produced a continuous reading of 14.57v with the engine running. I imagine this is what it should be.

 

The other (original) alternator (white) which was charging a bank of three brand new Banner 110Ah batteries produced a battery reading initially at 12.4v and never got above 13.6v. Concerningly the ampage reading showed 40-50 amps going into the battery bank for nearly an hour, then basically zero amps for another hour (approximately). At some point the alternator went back to producing just over 40 amps, then my phone battery died! At the end of a 4 hour trip I had only got the batteries back to 83% capacity (after staring at 72%). When the RCR chap fitted the starter motor alternator he checked the voltage on both alternators and the services alternator (white) seemed to be producing 14.59v at that time. A check of connections shows all to be clean and tight.

 

Have I got a dodgy alternator (it will be about ten years old)? If so, does anyone know the make that RCR supply; they don't seem to list alternators in their on-line shop.

 

Any help would be appreciated.

[Tracy D'arth]

AAArgg!   Where to start?

 

The cabin battery alternator is not fully charging the batteries. What amperage is it?

 

Could you get RCR back?   Can you post photos of the alternator?

[ditchcrawler]

11 minutes ago, Tracy D'arth said:

AAArgg!   Where to start?

 

The cabin battery alternator is not fully charging the batteries. What amperage is it?

 

Could you get RCR back?   Can you post photos of the alternator?

I don't think RCR will cover the domestic alternator.

[Tracy D'arth]

Just now, ditchcrawler said:

I don't think RCR will cover the domestic alternator.

Good point, pretty useless then.  It would help if we knew where the OP was, maybe Bugsworth, maybe not.

[ditchcrawler]

34 minutes ago, Bugsworth Tippler said:

 

 

The other (original) alternator (white) which was charging a bank of three brand new Banner 110Ah batteries produced a battery reading initially at 12.4v and never got above 13.6v. 

Have you actually measured the voltage output on the back of your domestic alternator while it is charging?

[Bugsworth Tippler]

23 minutes ago, ditchcrawler said:

Have you actually measured the voltage output on the back of your domestic alternator while it is charging?

I had to rush home and leave the boat today but I'll be back tomorrow to take that reading. It was 14.59v when the RCR chap measured it.

 

In answer to another comment I'm not at Bugsworth but moored at Higher Poynton on the very shallow Macc.

 

And the alternators are both 90amp.

 

Edited May 23, 2022 by Bugsworth Tippler

[Tony Brooks]

1 hour ago, Bugsworth Tippler said:

The other (original) alternator (white) which was charging a bank of three brand new Banner 110Ah batteries produced a battery reading initially at 12.4v and never got above 13.6v. Concerningly the ampage reading showed 40-50 amps going into the battery bank for nearly an hour, then basically zero amps for another hour (approximately). At some point the alternator went back to producing just over 40 amps, then my phone battery died! At the end of a 4 hour trip I had only got the batteries back to 83% capacity (after staring at 72%).

 

1. An alternator automatically depresses its voltage as the current rises so at maximum output the charging voltage may be sub 13 V.

 

2. The OP quotes % charges so unless he is one of  a very few knowledgable boaters who can deal with BVMs this reading is probably plain bullshine or a lie.

 

3. While one hopes the alternator high rated output without an identification we don't know what it is, so it might be an 70 amp alternator and if so I am sure 40 to 50 amps may well be in the range where the charging voltage is depressed.

 

I think this might just be very discharged batteries. For goodness sake ignore those % charged readings. When you get back to the boat run the engine at a speed that maintains the highest charging amps it can, you will have to gradually reduce the speed as the charging current drops to minimize the fuel used. Keep going for many hours until the charging current has dropped to about 3 to 6 amps and has stopped dropping over half an hour or so. Then come back with the charging voltage/ If at that time it is less than about 14.2 to 14.4V then it indicates the alternator may have a failed diode. However, I don't think that you will find that. Make sure the drive belt is in good condition and correctly tensioned.

 

Note: the only scales on the BVM that can be assumed accurate are Volts, amps, and Ah out.

[Bugsworth Tippler]

39 minutes ago, Tony Brooks said:

 

1. An alternator automatically depresses its voltage as the current rises so at maximum output the charging voltage may be sub 13 V.

 

2. The OP quotes % charges so unless he is one of  a very few knowledgable boaters who can deal with BVMs this reading is probably plain bullshine or a lie.

 

3. While one hopes the alternator high rated output without an identification we don't know what it is, so it might be an 70 amp alternator and if so I am sure 40 to 50 amps may well be in the range where the charging voltage is depressed.

 

I think this might just be very discharged batteries. For goodness sake ignore those % charged readings. When you get back to the boat run the engine at a speed that maintains the highest charging amps it can, you will have to gradually reduce the speed as the charging current drops to minimize the fuel used. Keep going for many hours until the charging current has dropped to about 3 to 6 amps and has stopped dropping over half an hour or so. Then come back with the charging voltage/ If at that time it is less than about 14.2 to 14.4V then it indicates the alternator may have a failed diode. However, I don't think that you will find that. Make sure the drive belt is in good condition and correctly tensioned.

 

Note: the only scales on the BVM that can be assumed accurate are Volts, amps, and Ah out.

 

I was aware of the unscientific nature of the % values and nearly included a qualifying comment in my post. I don't think the batteries would be discharged as they were continuously attached to a mains powered battery charger for a week or more just before my short trip. However, I'll try to implement your suggestions Tony. The main concern was the drop of amps in from 40+ to very near zero (the BVM actually showed amps going out, presumably due to fridge consumption).

 

I'll identify the alternator tomorrow and report back on any additional info. As I said I had to leave for home quickly and the rain was another reason for not emptying the rear deck to lift the lid on the engine bay.

 

Thanks again for the advice.

Ian

[Tony Brooks]

If the mains charger did keep the batteries more or less fully charged then the symptoms tend to suggest an alternator problem, but it could just as easily ba a wiring fault. Check the condition of the multiway connector(s) that are usually in the main wiring harness.

[Bugsworth Tippler]

23 minutes ago, Tony Brooks said:

If the mains charger did keep the batteries more or less fully charged then the symptoms tend to suggest an alternator problem, but it could just as easily ba a wiring fault. Check the condition of the multiway connector(s) that are usually in the main wiring harness.

I'll check the multiway connector tomorrow.

Thanks

[Bugsworth Tippler]

Just an update :

When I went to the boat today the service battery voltage was 12.65V and the starter 12.79V.

The 'dodgy?' alternator is as supplied by Isuzu (HMI Part No. 900383-ALS). The alternator as supplied by RCR has no identification marks that I could find.

 

I checked the wiring and the connector block but everything seemed fine.

 

With the engine running the battery voltage (as read by the BVM) was 13.0-13.1V and the current flowing into the battery bank was all over the place ranging from 5A to 30A.

 

When the engine was revved the voltage remained steady at 13.0V and the current input went down to 4-5 amps.

 

After a while I switched off the engine and connected the mains operated 20 amp 7-stage Smart Battery Charger.
https://www.alpha-batteries.co.uk/12v-20a-connect-forget-automatic-leisure-battery-charger/

 

The voltage reading was then 13.1V and the current flow to the battery bank was approximately 20amp. The percentage reading started to rise from the previous reading of 83%.

 

I know it would be very useful to have measured the voltage from the alternator but for safety reasons I chose not to risk being in the engine bay with a working engine.

 

I have enquired of RCR as to the make of the alternator they supplied. They will get back to me. If not too expensive I shall buy a new alternator to have as a backup should problems continue with the current one on my summer trip. I may also get an expert to check the system though if the alternator 'problem' is intermittent this may or may not help.

 

I'm not sure this additional information would help anyone who knows about these things so I'll thank all those who helped previously in case this is the last post.

 

 

[Tony Brooks]

As long as the engine was revving at 1200 rpm plus  then you should have got well over 14 volts with batteries well on their way to being fully charged (2.65) so if the drive belt is tight I suspect it is a faulty alternator. Probably lost a diose or two, but with erratic output it could be a bad solder joint or perhaps worn out brushes. Any chance of a photo of the terminal end of the alternator so we can see what it is.

Edited May 24, 2022 by Tony Brooks

[Bugsworth Tippler]

37 minutes ago, Tony Brooks said:

As long as the engine was revving at 1200 rpm plus  then you should have got well over 14 volts with batteries well on their way to being fully charged (2.65) so if the drive belt is tight I suspect it is a faulty alternator. Probably lost a diose or two, but with erratic output it could be a bad solder joint or perhaps worn out brushes. Any chance of a photo of the terminal end of the alternator so we can see what it is.

 

Is this picture any use?

[Tony Brooks]

9 minutes ago, Bugsworth Tippler said:

 

Is this picture any use?

 

 

It looks like it ha s similarities to the Lucas A127 so the regulator is the funny shaped thing between 7 & 9 o'clock. The brushes are almost certainly mounted on it so if you undo the three small securing screws and very carefully start to lift it so you can pull the blade connector you can then see off. Then sort of twist the outer edge upwards and move the regulator to the left so you can get the brushes to clear the aperture.  Make sure you look down the hole at the two brass/copper slip rings to ensure they are not worn through. The brushes and slip rings look OK the chances are you need the alternator overhauled.

[Bugsworth Tippler]

Thanks Tony

 

I will get the alternator looked at and maybe buy a new one.

 

Ian

[Tracy D'arth]

That looks like A Leece Neville alternator, which is a 90A Prestolite.  A127pattern. Very conventional. It has an insulated negative lead, the lower thick cable, the thick positive cable and the D+ connection. The W tacho connection seems not to be used.

 

 

[Tracy D'arth]

7 minutes ago, Tracy D'arth said:

That looks like A Leece Neville alternator, which is a 90A Prestolite.  A127pattern. Very conventional. It has an insulated negative lead, the lower thick cable, the thick positive cable and the D+ connection. The W tacho connection seems not to be used.

 

 

Good alternator rebuilder in Macclesfield.

 

Macclesfield Auto Electrics

 5.0 (1 Rating) | Write a review

 Unit 2 Albion New Mill London Rd, Macclesfield, SK11 7QX Directions

Tel01625 425396

[nicknorman]

I don’t think there has been any mention of alternator warning lights? This is a 9 diode machine and needs current through the warning light for it to start working. Hard to see exactly in the photo,  but the wire coming from the D+ looks a bit dodgy. Anyway, if the warning light associated with this alternator isn’t coming on before start, that is a problem.

 

You can check the voltage on the D+ with ignition on but engine not running. It should be a couple of volts or so. If it is zero, there is a problem with the warning light circuit / bulb etc. If it is around 12v the problem lies within the alternator.

[GUMPY]

10 hours ago, Bugsworth Tippler said:

 

Is this picture any use?

The number on the alternator 900383-als comes back as a Prestolite alternator with insulated return.

[Tracy D'arth]

As I said.

[Bugsworth Tippler]

5 hours ago, nicknorman said:

I don’t think there has been any mention of alternator warning lights? This is a 9 diode machine and needs current through the warning light for it to start working. Hard to see exactly in the photo,  but the wire coming from the D+ looks a bit dodgy. Anyway, if the warning light associated with this alternator isn’t coming on before start, that is a problem.

 

You can check the voltage on the D+ with ignition on but engine not running. It should be a couple of volts or so. If it is zero, there is a problem with the warning light circuit / bulb etc. If it is around 12v the problem lies within the alternator.

 

I've been out and about so missed the last few postings. I have taken the alternator out of the boat and to Manchester Auto Electrical who were recommended to me. I obviously didn't check the voltage on the D+ but it would have been useful to have done so and I will be able to do so in future (see below). I think the connection to D+ was good (closer view attached). I think the warning light was functioning.

The chap at Manchester Auto Electrical pointed out that beneath the Isuzu label was a Prestolite label but he didn't have anything good to say about them as they seem to use their own parts which are not easy for him to get. However, he has sourced an identical replacement which I should get tomorrow.

The Macclesfield Auto Electrics would have been useful to know before I drove to Salford but never mind. I'll file that info away.

 

Thanks to everyone for their advice.

Ian

[nicknorman]

5 minutes ago, Bugsworth Tippler said:

 

I've been out and about so missed the last few postings. I have taken the alternator out of the boat and to Manchester Auto Electrical who were recommended to me. I obviously didn't check the voltage on the D+ but it would have been useful to have done so and I will be able to do so in future (see below). I think the connection to D+ was good (closer view attached). I think the warning light was functioning.

The chap at Manchester Auto Electrical pointed out that beneath the Isuzu label was a Prestolite label but he didn't have anything good to say about them as they seem to use their own parts which are not easy for him to get. However, he has sourced an identical replacement which I should get tomorrow.

The Macclesfield Auto Electrics would have been useful to know before I drove to Salford but never mind. I'll file that info away.

 

Thanks to everyone for their advice.

Ian

Actually it was further back along the wire where I thought there was a connection, but now I look again it’s just where the wire disappears into sheathing. False alarm!

 

You can get quite a bit of info from the D+/bulb circuit. If the light comes on with engine not running, it implies that the circuit through the brushes /rotor is good, but advice is to remove the belt and spin the alternator - if the light flickers, almost certainly the brushes have worn to the point of not working.

[Alan de Enfield]

40 minutes ago, Bugsworth Tippler said:

he chap at Manchester Auto Electrical pointed out that beneath the Isuzu label was a Prestolite label but he didn't have anything good to say about them as they seem to use their own parts which are not easy for him to get. However, he has sourced an identical replacement which I should get tomorrow.

 

 

So, there was something wrong with it - what was it ?

 

Was this the alternator that was replaced by RCR (I've sort of lost track of which one was faulty, which one was replaced and which one was subsequently faulty).

 

I have heard that RCR will re-use faulty parts taken off / replaced on other boats - is this the case here ?

[nicknorman]

4 minutes ago, Alan de Enfield said:

 

 

So, there was something wrong with it - what was it ?

 

Was this the alternator that was replaced by RCR (I've sort of lost track of which one was faulty, which one was replaced and which one was subsequently faulty).

 

I have heard that RCR will re-use faulty parts taken off / replaced on other boats - is this the case here ?

It is the old alternator, not the one replaced by RCR.

[Bugsworth Tippler]

The ten year old alternator which charged the service batteries was the one which was faulty and which I am now getting replaced. The identical one (same make and age) which charged the starter battery was replaced a couple of weeks ago by RCR. I realise now that both had been giving less than the optimum output voltage for some time but the starter battery alternator had developed a mechanical problem and literally stopped rotating.

 

I don't know the exact fault on the service battery alternator but may investigate.

Edited May 25, 2022 by Bugsworth Tippler