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I know there is another thread running on Alternators burning out but I didnt want to derail Steve's thread into my problems. Bottom line is one of my alternators looks like it is on the point of expiry....and I want have a plan in place for when it does.

It is a Beta 43 engine with what looks like the original 2 alternators, one a 55A for the start battery and a 90A for the domestic (as identified on the survey - I havent a clue). This is how they were wired when we bought the boat a year ago ......but the max voltage during Absorption was always below 14V so in September we fitted a Sterling A to B where both alternators are wired into the AtoB and then go to both sets of batteries. Since fitting the AtoB we have done circa 200 hrs engine running and charging has been fine. Our typical useage is 100Ahrs out by the end of the night (660Ahr domestic bank) so 85% SoC when starting the engine in the morning to recharge .....and then around 60A generated on start up reducing in the first hour to 30-40A, so not a massive duty for the alternators to cope with.

When out yesterday, I though it would be interesting to use my infrequent red thermometer to see what sort of temps I was seeing around the engine. On the fully warmed up engine (90 mins of running ...with 60A down to 30A charging), the top of the engine block was 70°C (the thermostat setting), the 90A alternator was 45°C and the 55A alternator was 85°C. Looking at the smaller alternator there was a lot of 'soot' around the front air vents so obviously some excessive heat in there. There is a picture below of the alternator. I am therefore concerned it is getting too hot and will likely give up sometime soon.

A few questions.

1) If it overheats and gives up, is it just the electrical side that will die or will it affect the turning of the alternator....as that belt also drives the water pump. If its just electrical, I can live with that as the 90A alternator should still be fine...well at least for a while.

2) Would a better plan be to disconnect the red cable now and therefore not use that alternator. As in (1) will the alternator be ok mechanically so the water pump runs fine. Do I need to disconnect anything from the AtoB? I need to read the manual. I can then look to buy a good replacement.

3) I need to replace the unit - that is obvious- but what should i replace it with? I will not get it refurbished.......advice from other thread. I could buy an new Beta alternator but will it just be a straight swap. Is the pulley on mine likely to be the  same as the new one? I dont want to have to start changing pulleys. A 55A Beta replacement will likely still have the same issue as these are designed to recharge a start battery and not continuous duty  charging a domestic bank, but I am likely to only be charging the final 20% so not too high a current. I always fancied a Balmar alternator but if I go for one (or another make) that is more designed to put in power, I gues they will need some modification to brackets, belts, wiring etc. Is there another drop in replacement that will work without any faffing? If there is no faffing needed, I can do it myself, otherwise I will have to get someone in to do it. Any recommendations for someone good a faffing in the Napton/Braunston area....or a good place to go and buy an alternator...so I can see it is the same?

The moral of this is dont buy an infrequent red thermometer.

 

alternator-113741.jpg

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How hot should it be?

Do you trust your thermometer?

Is belt tension correct?

Can you remove belt and rotate by hand to determine if bearings are ok?

Is it worth cleaning to see if it makes any difference?

Have you had a cup of tea yet?

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Maybe your 55 amp alternator is doing more than its fair share of the work. Do you have a clip on ammeter. If that is the case maybe you would be better off running them separately, it was probably only designed to recharge a starter battery

I think in a majority of cases they fail electrically and spin happily but I had one do the opposite and the rotor moved back because the bearing housing failed. I wouldn't suggest disconecting it, but if you go to a reputably company when it fails then a repair should be as good as a new one.

 

 

 

Edited by ditchcrawler
Added a bit
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33 minutes ago, rusty69 said:

How hot should it be?

Do you trust your thermometer?

Is belt tension correct?

Can you remove belt and rotate by hand to determine if bearings are ok?

Is it worth cleaning to see if it makes any difference?

Have you had a cup of tea yet?

Dunno how hot, but one is 45 deg and the small one is 85 deg with soot round the vent holes. Is this too hot? Can alternators work at this temp?

Trust the thermometer....yes, to within 5 degrees.

Belt tension is a tad slack but nothing out of ordinary.

Not tried removing belt.

I will clean it.

Blackcurrant and vanila tea. Very nice.

On thought is that I had a re-wire done fitting new battery charger etc etc a few weeks back and one thing I got the guy to do was to put the AtoB temp sensors on - when the AtoB was orginally fitted the temp sensors were not connected. I wonder if they have been put on the wrong way round. I will check.

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13 minutes ago, ditchcrawler said:

Maybe your 55 amp alternator is doing more than its fair share of the work.

I think in a majority of cases they fail electrically and spin happily but I had one do the opposite and the rotor moved back because the bearing housing failed. I wouldn't suggest disconecting it, but if you go to a reputably company when it fails then a repair should be as good as a new one.

 

 

 

Yes, that's what I was thinking that the small one is working harder. Maybe the temp probes have been fitted the wrong way round. First thing to look at. If it fails electrically, so no current flowing, is that likely to cause an issue to the AtoB? I will read the manual.

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3 minutes ago, Dr Bob said:

Trust the thermometer....yes, to within 5 degrees.

 

I bought a infrequent red thermometer when they fist came out and the poxy thing gave a wide range of inaccurate results depending on the colour and finish of the surface it was aimed at. Recently I met a bloke whose whole career had been designing the things and he said they are much better now except for the cheap ones. To get a decently accurate one costs north of £100, he said IIRC.

Your alternator however, looks to me like belt dust. If so, then as DC implied it is simply working hard and wearing the vee belt. Might be nothing wrong with it. 

Get a clamp meter. Even more fun than a infrequent red thermothingy!

 

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8 minutes ago, dor said:

"soot" on the front of an alternator often comes from the belt, due to being too tight or out of alignment

 

1 minute ago, Mike the Boilerman said:

 

I bought a infrequent red thermometer when they fist came out and the poxy thing gave a wide range of inaccurate results depending on the colour and finish of the surface it was aimed at. Recently I met a bloke whose whole career had been designing the things and he said they are much better now except for the cheap ones. To get a decently accurate one costs north of £100, he said IIRC.

Your alternator however, looks to me like belt dust. If so, then as DC implied it is simply working hard and wearing the vee belt. Might be nothing wrong with it. 

Get a clamp meter. Even more fun than a infrequent red thermothingy!

 

You are both right that the 'soot' could be belt wear. I will take a closer look. The temperatures can be all over the place with these meters but the high temps showed all over the 55A alternator so I am pretty sure it was a lot hotter.

I think if its not going to do any damage leaving it as is, and if it burns out it wont damage the AtoB, then Plan A might be to leave things as they are and suss out the best drop in replacement for when it does fail.

Any comments on the best 'drop in' replacement?

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2 hours ago, WotEver said:

^^^^^ this. 

 

Except the internal fan blows out through the slots so I would have thought it would tend to blow belt dust away. Could be brush dust.

I think we need two sets of voltage and current readings with the A to D bypassed so we can find out which alternator was only giving 14 volts. I suspect fitting the A to D covered up another fault. - that is as long as you were running for many hours before taking the reading. If it was only an hour or two then 14V may be normal.

causes of low charging voltage with well charged batteries are:-

Diode or single phase fault.

Batteries still drawing too much current for some reason.

Just possibly very worn brushes making intermittent contact but if it was this the relevent alternator would have stopped charging with no warning lamp some time ago.

 

 

 

 

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Almost certainly belt dust. Three things go wrong with those alternators. Mostly brush wear, easily fixed. Sometimes rotor goes open, sometimes corrosion between stator and drive end bracket bursts the bracket itself. They don't generate soot.

Two internal fans. The front one draws air from the middle behind the pulley and out at the periphery so thats where I would expect belt dust to be deposited.

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1 hour ago, Tony Brooks said:

 

I think we need two sets of voltage and current readings with the A to D bypassed so we can find out which alternator was only giving 14 volts. I suspect fitting the A to D covered up another fault. - that is as long as you were running for many hours before taking the reading. If it was only an hour or two then 14V may be normal

 

Tony, prior to installing the AtoB only the 90A alternator was connected to the battery monitor and domestic, so that is the one that I referred to as not delivering the 14V. I think it is common that some these old (2002-5) alternators do not kick out 14V - this is the 2nd boat I have had with one like this, Gibbo refers to them in his Smartgauge bumf and the Sterling info suggests the same. As for timing, it never got to 14V during the absorption phase. I dont think there was anything wrong with the alternators at the time we fitted the AtoB as all charging behaviour with the AtoB has been totally normal since. I've done best part of 400 engine hours since we got the boat and I dont think the alternator charging has changed at all. I am only worried now I have started measuring temperatures in the engine bay.

In your opinion is 85°C too hot for an alternator considering the other one was at 45°C?

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1 hour ago, Sir Nibble said:

Almost certainly belt dust. Three things go wrong with those alternators. Mostly brush wear, easily fixed. Sometimes rotor goes open, sometimes corrosion between stator and drive end bracket bursts the bracket itself. They don't generate soot.

Two internal fans. The front one draws air from the middle behind the pulley and out at the periphery so thats where I would expect belt dust to be deposited.

Sir Nibble, Thanks for that. Would you be happy with temperature (85°C)? Maybe I am worrying about nothing?

If I wanted to replace it, I could just do a like for like swap but these alternators are designed only to recharge a starter battery. Are there any 'drop in' replacements ie with the right pulley, fittings and wiring that would give a reasonable current for  reasonable time (ie 2-3 hours). Balmar sound like top of the range but not sure how 'drop in' they are going to be and would I then have a problem with the AtoB as they seem to have sophisticated regulator hardware built in?

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From one of Gibbo's old posts:-

 

"

The colder the better, within reason. Obviously if you run one at minus 100 degrees C it won't be too happy.

 

The rectifier diodes (depending upon the type) will be happy up to about (rarely) 85 degrees C or (more commonly) 105 degrees C (the two most common ratings). But for them to stay at that temperature the air temperature and alternator casing temperature would have to be substantially lower as they heat themselves quite a lot.

 

As the temperature increases the resistance of the stator increases quite a lot which reduces the maximum current capability of the alternator. It also, as a result of the increased resistance, generates even more heat.

 

Finally most internal regulators measure the temperature and reduce the alternator output to protect the alternator.

 

Surrounding air temperature higher than about 30 degrees C will start to reduce alternator output but they are actually safe up to about 60 degrees C surrounding air temp.

 

Gibbo"

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6 minutes ago, rusty69 said:

From one of Gibbo's old posts:-

 

"

The colder the better, within reason. Obviously if you run one at minus 100 degrees C it won't be too happy.

 

The rectifier diodes (depending upon the type) will be happy up to about (rarely) 85 degrees C or (more commonly) 105 degrees C (the two most common ratings). But for them to stay at that temperature the air temperature and alternator casing temperature would have to be substantially lower as they heat themselves quite a lot.

 

As the temperature increases the resistance of the stator increases quite a lot which reduces the maximum current capability of the alternator. It also, as a result of the increased resistance, generates even more heat.

 

Finally most internal regulators measure the temperature and reduce the alternator output to protect the alternator.

 

Surrounding air temperature higher than about 30 degrees C will start to reduce alternator output but they are actually safe up to about 60 degrees C surrounding air temp.

 

Gibbo"

Thanks Rusty. The Sterling manual says that there is just one temperature probe to the alternators and that 90°C is the cut off when the Sterling reduces the load....so connect the temp probe to the hotest alternator. That sort of fits with the temps you quoted from Gibbo.

Sounds like I am very near the limit but maybe the internal regulator is reducing output as you say. Maybe I need to fit a fan near it?

 

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15 minutes ago, Dr Bob said:

Sir Nibble, Thanks for that. Would you be happy with temperature (85°C)? Maybe I am worrying about nothing?

If I wanted to replace it, I could just do a like for like swap but these alternators are designed only to recharge a starter battery. Are there any 'drop in' replacements ie with the right pulley, fittings and wiring that would give a reasonable current for  reasonable time (ie 2-3 hours). Balmar sound like top of the range but not sure how 'drop in' they are going to be and would I then have a problem with the AtoB as they seem to have sophisticated regulator hardware built in?

I would be happy with that temperature yes. It's not ideal but you are working the machine pretty hard. There is nothing sophisticated about the internal regulator in a Belmar, it's a standard delco part, but not even genuine delco but a pattern part made by transpo. How about a picture of the other alternator that was charging low.

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2 minutes ago, rusty69 said:

Ah, an Alto-fan.

 

What I need is a fan that doesnt need any power. Can sit on something around 70-80°C and use that heat energy to turn the fan blades. It would need to turn pretty fast. Can you think of anything?

I'm just going out to take another photo for Sir Nibs. Have a think while I am gone.

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37 minutes ago, Sir Nibble said:

I would be happy with that temperature yes. It's not ideal but you are working the machine pretty hard. There is nothing sophisticated about the internal regulator in a Belmar, it's a standard delco part, but not even genuine delco but a pattern part made by transpo. How about a picture of the other alternator that was charging low.

Sir Nibs, here are a couple of shots of the 90A alternator. I think it is the original supplied on the engine (Beta 43) - from 2002. Not a lot of space around it so apologies for the poor shots. This is on the RHS of the engine, looking forward.

alternator-183315.jpg

alternator-183300.jpg

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It's a bosch machine sensed unit. Should produce well better than 14V, probably around 14.4 minimum. Looks like there is either a voltage drop issue or a diode problem. Check the voltage on each of the two terminals, B+ to  case and D+ to case. They should pretty well match. In any event if the delivery is down that will explain why the little one is being flogged. It might be a good idea to take the sterling unit out of the system until we get to the bottom of this.

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I think you will have to update your infrequent red thermomoter thread to include alternator testing and diagnosis. 

If no traditional instruments are available, or  remote diagnostics are required by inference then whip out your infrequent red thermometer (other thermometers are available). 

Testing can be undertaken whilst waiting for locks without leaving the comfort of your tiller. 

Edited by rusty69
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1 hour ago, Sir Nibble said:

It's a bosch machine sensed unit. Should produce well better than 14V, probably around 14.4 minimum. Looks like there is either a voltage drop issue or a diode problem. Check the voltage on each of the two terminals, B+ to  case and D+ to case. They should pretty well match. In any event if the delivery is down that will explain why the little one is being flogged. It might be a good idea to take the sterling unit out of the system until we get to the bottom of this.

Thanks Sir Nibs. I will check the two terminals tomorrow. We've just got back to the marina after being out for a week and likely to stay put until early next week so not going to be running the engine for charging. Not sure how to take the sterling out of circuit and could be tricky given the direction of the wiring. The 90A unit has been working the same for 12 months but I understand what you are saying.

Can I just disconnect the 55A unit by taking the cable off the B+ terminal - or will that wreck that alternator......or just re-route the cable from the B+ terminal direct to the starter battery? The starter battery has likely not got much life left...it looks quite old. The 6 domestic 110's are 12 months old and still in very good condition <10% loss in capacity based on resting voltage at various discharge SoCs.

I'll let you know the voltages tomorrow.

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