MD 2030 Alternator Wiring Conundrum

[MBH]

Hi,

I have a Volvo MD2030 fitted into a Bavaria 32. Unfortunately the engine was fitted by a total muppet who made a complete cock of it. Whilst sailing across the Bay of Squillace at night at end the end of last year over Volt alarms started going off all over the place. On inspection the Alternator was charging at up to and over 18v! Dropping the revs to just above tick-over brought the charging voltage down to about 14 ish volts - however this resulted in making way at about half a knot and sod all wind! To get us into port I disconnected the alternator and ran into port on the batteries. As the alternator was obviously screwed I felt I had nothing to lose at that point!

On closer inspection there were two wires coming off of the alternator B+ post, one connected to the centre terminal of a Multi battery isolator the other shorter cable was tucked behind the starter motor uninsultated and connected to nothing and shorting out on the engine block. I suspect this is what blew the voltage regulator in the alternator. Having bit the bullet and shelled out on a new Alternator I want to make sure I connect it correctly.

I am assuming that the unconnected cable should have gone somewhere but the alternator may have been off of another boat so the second cable may indeed be redundant. On looking at the MD2030 wiring diagram it looks like there is a cable from the alternator B+ to the starter motor but the diagram doesn't show a multi battery isolator so I am unsure whether the wiring diagram is correct for my boat.

My thinking is that if the Alternator is connected both to the multi battery isolator and the Starter motor, would that not make the multi battery isolator moot as charge will be going down the starter motor cable and the isolator to the starter battery. From what I can make out the multi battery isolator is a couple of diodes that allows charge from the alternator to go to both batteries simultaneously but not allow charge to run back to the alternator being blocked by the diodes in the isolator.

The only reason I cant think of to connect the alternator to the starter motor is to give it an extra kick when starting. But once running surely its going to be pushing charge directly through the starter motor cable and the multi battery isolator.??

Unfortunately being both a newbie and not having a correctly wired example to start with I'm a little lost!

Any light anyone could throw on this subject will be greatly received.

thanks in advance.

[Dsanduril]

It is pretty common in the factory setup to have the alternator B+ wired to the starter positive. That way when you install the engine you only have to run one big wire from the battery to the starter (and a negative of course). When you start the engine electricity comes from the battery to the starter, the alternator is sitting there dumb as a rock. Once the engine, and the alternator, start spinning the output from the alternator goes through the cable to the starter post and then to the battery. The starter solenoid is open at this point, so the starter is now dumb as a rock and not involved.

What complicates things is when you are a second (house) bank to the system, if you want the house and starter to be separate then you have to put in some form of isolation. The most common would be to leave the original system alone, and to add a wire from the alternator (or the starter battery +, or anyplace else convenient) to the isolation device. That way when the alternator is charging both batteries get charged, and if the isolator fails or the house bank gets disconnected you don't blow up the alternator as it can still charge the start battery.

There are a ton of variations on that setup, and as many more reasons for and against each of them, but that's the common configuration.

It sounds like your isolation device has one input and two outputs - one to the house bank and one to the starter battery? Then when someone put that in place they disconnected the cable that used to run to the starter post and just left it hanging - bad form. Then they hooked the alternator direct to the isolator and the the two batteries to the outputs. This is another common installation scenario (except for leaving the old cable hanging ).

I'll let someone else here voice preferences, both will work and do the job of directing charging from one alternator to two batteries. Also there are lots of opinions about isolation devices, B2B chargers, etc.

[smac999]

the factory setup of the motor is to feed the alt b+ to the start post. this charges the engine battery only. using the large cable of the starter.

a boat builder or owner could then remove that wire and feed the alt elsewhere. IE to your isolator. when this is done the the other wire must be removed. sometimes it can't be if it's in the factory harness. so both ends should be disconnected and protected somehow. sounds like it was disconnected so it would work probally. but left not protected.

[MBH]

Hi Guys,

Thanks a million for the advise, confirms what I was thinking but always nice to do something with the confidence it's the right way to do it. Alternator -> Starter cable will be left out and will wire straight to the splitter.

Fair winds and following seas.

BR MBH.

[FULLCIRCLE331]

Attached a photo of my alternator. On my MD2030, 2005 BENATEAU 331 I bought in 2008. I had a similar problems and changed the alternator twice, each time appeared to fixed the problem. Researched on Benateau owners, my problem is common and is often ignored. my voltmeter, tachometer and amp meter flicker or drop out. Current not to sever. I have 240 watts of solar that keeps my batteries charged on the mooring. I also have an isolator distributing the charge that could be the problem. Have checked wiring with little affect.

[belizesailor]

Originally Posted by FULLCIRCLE331

Attached a photo of my alternator. On my MD2030, 2005 BENATEAU 331 I bought in 2008. I had a similar problems and changed the alternator twice, each time appeared to fixed the problem. Researched on Benateau owners, my problem is common and is often ignored. my voltmeter, tachometer and amp meter flicker or drop out. Current not to sever. I have 240 watts of solar that keeps my batteries charged on the mooring. I also have an isolator distributing the charge that could be the problem. Have checked wiring with little affect.

What was the problem/solution?

[FULLCIRCLE331]

Not charging no tack, voltmeter or amp meter. intermittent problem better with new alternator but not a permanent fix.

[belizesailor]

Originally Posted by FULLCIRCLE331

Not charging no tack, voltmeter or amp meter. intermittent problem better with new alternator but not a permanent fix.

Given that you replaced the alternator, its unlikely an alternator problem. Is it internally or externally regulated?

[Dsanduril]

The MD20x0 series use an earthing relay to connect the negative of the battery/alternator to the earthing connection when the engine is running. Bad contact inside this relay, or dirty connections around it can cause all the symptoms you describe.

As a test you can wire in a bypass of this relay, it won't cause any harm to do so for a short time. Then start the engine and see if the problems are solved.

[belizesailor]

Originally Posted by Dsanduril

The MD20x0 series use an earthing relay to connect the negative of the battery/alternator to the earthing connection when the engine is running. Bad contact inside this relay, or dirty connections around it can cause all the symptoms you describe.

As a test you can wire in a bypass of this relay, it won't cause any harm to do so for a short time. Then start the engine and see if the problems are solved.
Attachment 211257

Ive noticed this earth relay in the wiring diagram before, but have not encountered it on my engine (have had no need to go looking for it). The glow and start relays are installed in a box on the side of the engine (as is the norm in the MD series), but where is this earth relay usually hidden?

[DougR]

Originally Posted by Dsanduril

The MD20x0 series use an earthing relay to connect the negative of the battery/alternator to the earthing connection when the engine is running. Bad contact inside this relay, or dirty connections around it can cause all the symptoms you describe.

As a test you can wire in a bypass of this relay, it won't cause any harm to do so for a short time. Then start the engine and see if the problems are solved.
Attachment 211257

As noted by another poster, they (and I as well) have never seen this relay on a 2030 engine.......

I think this schematic is a limited application schematic, specifically for an isolated electrical system engine. You will note that the grounding relay is controlled by an orange colored wire coming off the glow control relay. That is, it only functions when the glow plug relay is energized. The glow plug relay is only energized when the key switch is in the glow or the start position. It is not energized during the normal “run” position, so it shouldn’t have any effect on alternator charging.

On the standard 2030 production the block was grounded, and the alternator B- went to the block. In this Beneteau application they might have modified the system to include an isolated engine block, and ran the alternator B- into the harness. Certainly the continuous issue would have me checking the wiring connections on both the + &- side of the alternator.

DougR

Edit....The isolated block was used briefly on the 2030A model, but was then discontinued on the later B,C and all later models, which will not have the ground relay.

One additional thought.....Beneteau used, in their anchor windless system, a control relay which was connected to the alternator energize lead. The purpose was to disable the windless unless the engine was running. This can be seen in the photo.....the red wire, labeled #1, typically went to the windless control relay. If the engine was not running the relay was not energized and the windless wouldn’t function so the battery couldn’t be drained.
It may be that the relay control coil pulls enough current that the alternator won’t energize, and of course the tach won’t work. I would disconnect that red #1 wire from the alternator and see what happens.

[Dsanduril]

Originally Posted by DougR

....
Edit....The isolated block was used briefly on the 2030A model, but was then discontinued on the later B,C and all later models, which will not have the ground relay.

You beat me to it, I knew it was used on at least the A model, and gone by the D, but didn't know when it disappeared.

If one is fitted it looks a lot like a starter solenoid and is mounted to a bracket under the starter. It sort of looks like the starter has two solenoids; one mounted as per normal on the starter, and one mounted just beneath the starter (an easy place to reach and work on most boat installations )

[DougR]

Originally Posted by Dsanduril

You beat me to it, I knew it was used on at least the A model, and gone by the D, but didn't know when it disappeared.

If one is fitted it looks a lot like a starter solenoid and is mounted to a bracket under the starter. It sort of looks like the starter has two solenoids; one mounted as per normal on the starter, and one mounted just beneath the starter (an easy place to reach and work on most boat installations )

Had to think about it a few minutes.........
The isolated ground electrical system on the 2030A engine was a carry over from the last of the prior 2000 series engines. On the later 2000 series this system was instituted on the saildrive engines as a corrosion control device, to keep the saildrive completely isolated from the engine and vessel electrical system. So it was also incorporated into the new Perkins (ISM) series of engines.

However with the introduction of the 2030B engine, nylon or mylar bushings and gaskets were introduced in the flywheel housing and flywheel cover which supports the saildrive. These Mylar parts electrically isolate the saildrive from the engine and it’s electrical system, so it was no longer necessary to use a two pole system, and it was discontinued. These isolation bushings are still used successfully in today’s D1 and D2 series of engines.

[smac999]

Originally Posted by FULLCIRCLE331

Attached a photo of my alternator. On my MD2030, 2005 BENATEAU 331 I bought in 2008. I had a similar problems and changed the alternator twice, each time appeared to fixed the problem. Researched on Benateau owners, my problem is common and is often ignored. my voltmeter, tachometer and amp meter flicker or drop out. Current not to sever. I have 240 watts of solar that keeps my batteries charged on the mooring. I also have an isolator distributing the charge that could be the problem. Have checked wiring with little affect.

are the batteries full when it's cutting out?

full batteries + solar = pretty common for an alt to stop working. and loss of tach. next time it happens throw something over the solar and turn some lights or loads on. and see if the tach comes back right away.

[FULLCIRCLE331]

External regulatory. I have considered replacing it but I have checked the diodes and they appear to be good.