Alternator Ind light question

[Martin Megson]

Can you draw us a diagram of that?

 

The photo in the link shows the wiring to the two lamps at the left side of the panel. The top one is the red ign lamp and the lower one the green Adverc lamp. The whit oblong on the ign lamp is a 47ohm resistor.

 

On the lower lamp the yellow wire is connected to the Adverc and the red is the power from the ignition switch ( through a relay). There is a second red wire from that terminal to the ign light providing the power. The other red wire on the ign light seems to the connected to the D+ terminal of both alternators but I can't be sure. I suppose that would make sense in that the light will work for either alternator.

 

Photo

[by'eck]

Hi thanks for the quick reply. The wiring diagram only shows the domestic circuit but the d+ terminal of the engine alternator is also connected to the red ignition light shown in the diagram. The leisure batteries are at the same voltage as the B+ terminal. When I get off the flooded Thames I'll get it tested but it looks very much as you and Keeping up suggest.

 

Thanks again for all your help. Wiggly amps aren't my strong point.

 

As an aside, its not a good idea sharing an alternator warning light. Not even ideal sharing a single exciter source since you are charging two separate batteries which will probably be at slightly different voltages.

 

I would suggest fitting a second warning lamp with 3 watt bulb, dedicated to the starter alternator and fed from the starter batteries. i.e. one side connected to starter alt D+ and the other connected to the ignition switch directly (same feed as relay coil but not via it). This will save confusion and potential problems now and in the future.

[Keeping Up]

As an aside, its not a good idea sharing an alternator warning light. Not even ideal sharing a single exciter source since you are charging two separate batteries which will probably be at slightly different voltages.

 

I would suggest fitting a second warning lamp with 3 watt bulb, dedicated to the starter alternator and fed from the starter batteries. i.e. one side connected to starter alt D+ and the other connected to the ignition switch directly (same feed as relay coil but not via it). This will save confusion and potential problems now and in the future.

 

 

Agreed

[Martin Megson]

Thanks guys. Interestingly the Adverc installation manual actually suggests using a the same source to connect the exciter lead but I think boat builder has taken that a step further and connected it at the lamp. I'll try the changes you suggest to put it right after fitting a new alternator.

Edited February 10, 2013 by Meggers

[by'eck]

Thanks guys. Interestingly the Adverc installation manual actually suggests using a the same source to connect the exciter lead but I think boat builder has taken that a step further and connected it at the lamp. I'll try the changes you suggest to put it right after fitting a new alternator.

 

Same source as indicator lamp for that alternator but not for a second one feeding a different set of batteries

[Martin Megson]

I'll take your word as I'm no expert but the installation manual isn't explicit. I'm a bit surprised as the boat was built in 2003 and this system has been working ok for 9 years. I guess it only presents this problem when one of the alternators develops a fault. I'll get the system checked by an electrician as I don't want to start messing with it myself and making it worse.

[Keeping Up]

I've been thinking about the effect of parallelling two D+ connections to the same lamp.

 

The joint D+ connection will always rise to the higher of the two alternators' D+ output voltages, because of its rectifier diodes.

 

The first battery to reach a high output voltage will probably be the starter battery. Within a few minutes it will probably be fully charged so its alternator will be putting out a corresponding voltage on its D+, which will then be sensed by the second alternator, tricking it into thinking that the domestic bank is fully charged. At that point the domestic alternator will shut itself down.

 

Now think what happens if either one of the two alternators should have a faulty diode in its main rectifier (B+) stack. The D+ voltage will rise to typically 16v, and the other alternator will immediately shut itself down.

 

Basically without the Adverc the domestic batteries would never be charged; and if the domestic alternator goes faulty, the starter battery will never be charged because it doesn't have its own Adverc.

 

So parallelling doesn't seem like a good idea at all. Isolating them by using a relay as suggested above to provide a separate supply with its own lamp is a good idea. But make sure that the domestic indicator lamp is fed from the domestic bank, otherwise it will glow dimly while running if the domestic bank is low while the starter battery is well charged.

[Martin Megson]

I've been thinking about the effect of parallelling two D+ connections to the same lamp.

 

The joint D+ connection will always rise to the higher of the two alternators' D+ output voltages, because of its rectifier diodes.

 

The first battery to reach a high output voltage will probably be the starter battery. Within a few minutes it will probably be fully charged so its alternator will be putting out a corresponding voltage on its D+, which will then be sensed by the second alternator, tricking it into thinking that the domestic bank is fully charged. At that point the domestic alternator will shut itself down.

 

Now think what happens if either one of the two alternators should have a faulty diode in its main rectifier (B+) stack. The D+ voltage will rise to typically 16v, and the other alternator will immediately shut itself down.

 

Basically without the Adverc the domestic batteries would never be charged; and if the domestic alternator goes faulty, the starter battery will never be charged because it doesn't have its own Adverc.

 

So parallelling doesn't seem like a good idea at all. Isolating them by using a relay as suggested above to provide a separate supply with its own lamp is a good idea. But make sure that the domestic indicator lamp is fed from the domestic bank, otherwise it will glow dimly while running if the domestic bank is low while the starter battery is well charged.

 

Interesting. As I said I'm not an electrician so am having difficulty following all of this but what you say makes sense. I've just realised that while I have checked that the domestic alternator is connected to the alternator warning light and the Adverc green light as per the wiring diagram supplied with the boat I haven't actually confirmed that the engine alternator connected to this light, I just assumed it was. It may be that here is no indicator light on the engine alternator. I'll have a closer look tomorrow and see if I can isolate and trace exactly what the D+ terminal is actually connected to. Either way it think I need to replace the domestic alternator.

 

Can anyone recommend a good electrician or boatyard on the south Oxford who would be able to supply and fit an alternator.

[Martin Megson]

Having spent a couple of hours with a multimeter I now bette understand the mass of wiring in the engine bay. Rather embarrassingly I have found that there s in fact a separate warning light for the engine alternator built into the voltmeter. Logical I suppose but as there is also a bigger red light with the word Alternator under it on the panel I overlooked it. I'm now content that the service and domestic power systems are completely separate as you guys suggested they should be. I'm pretty sure there is a fault in the domestic alternator, probably a blown diode from you diagnosis and that my service alternator is ok. I plan to replace the faulty alternator as soon as I can get a new one and will update this thread when all is well.

 

Sorry to have wasted your time with poor diagnosis, I'm grateful for all the useful advice which has significantly increased my knowledge of the electrics.

[by'eck]

Having spent a couple of hours with a multimeter I now bette understand the mass of wiring in the engine bay. Rather embarrassingly I have found that there s in fact a separate warning light for the engine alternator built into the voltmeter. Logical I suppose but as there is also a bigger red light with the word Alternator under it on the panel I overlooked it. I'm now content that the service and domestic power systems are completely separate as you guys suggested they should be. I'm pretty sure there is a fault in the domestic alternator, probably a blown diode from you diagnosis and that my service alternator is ok. I plan to replace the faulty alternator as soon as I can get a new one and will update this thread when all is well.

 

Sorry to have wasted your time with poor diagnosis, I'm grateful for all the useful advice which has significantly increased my knowledge of the electrics.

 

Good luck with the repair Martin. Let us know what transpires.

[Martin Megson]

I got areplacement diode pack which I finally got time to fit today. Problem solved light working as it should and output voltage of around 14.4 on both B+ and D+ terminals .

 

Thanks again for all the helpful advice. I now knw much more about my charging system.

[Sir Nibble]

I got areplacement diode pack which I finally got time to fit today. Problem solved light working as it should and output voltage of around 14.4 on both B+ and D+ terminals .

 

Thanks again for all the helpful advice. I now knw much more about my charging system.

And there's you saying you're no good with "wiggly amps". Now you have traced a fault down past deciding the alternator is faulty and right down to component level, how many people do you know who would repair an alternator rather than replace? Satisfying?

[Martin Megson]

And there's you saying you're no good with "wiggly amps". Now you have traced a fault down past deciding the alternator is faulty and right down to component level, how many people do you know who would repair an alternator rather than replace? Satisfying?

 

Thanks. Very satisfying and I've learned a lot about the boats electrical system. Couldn't have done it without the helpful advice of forum members.

[Oakie]

I had the same problem recently. Check out my blog and see what I did about it:-

http://nbstronghold.blogspot.co.uk Date of post January 2013.

You could be at a disadvantage if you have no car as the address is:-

Victoria Road Service & MOT

Unit 8, Victoria Road Trading Estate

Victoria Road

Portslade

Brighton BN41 1XQ

01273 439944

 

Ask to speak to 'Terch'

 

Oops! I now see you managed to fix it. The contact address could still be useful on this forum though. Only for those living in the South of course!

Edited March 7, 2013 by Oakie

[Martin Megson]

To quote Victor Meldrew "I don't believe it!" After repairing my leisure alternator last week my engine alternator packed up yesterday. Luckily the only spare part I had on board was a regulator left over from the repair kit I bought for the other alternator. Since I had it to to hand I fitted it and bingo the alternator is now working fine. Managed to repair two alternators with one repair kit.