Warning light

[Tony Brooks]

Taking that lead off a running alternator may well cause internal damage. The idea is to take a measurement (in your case) by removing the red insulating stuff from the female blade, pushing the terminal back on, THEN starting and revving the engine. Next take the reading from the now uninsulated part of the female blade and the alternator case. Finally stop engine, remove female blade and re-insulate and replace.

 

If there is even a hint of slackness between the male and female blades I would gently squash the female blade a little to make it fit more tightly. It is just a push fit if there is no stud and nut and I do not think there is.

 

I regret that I do not understand "a reading of 15/81". Is it 15.81 volts? If so something else is wrong.

 

I fear it may be time to see if there are any more knowledgeable members nearby who would be willing to pop over to help.

 

 

[MtB]

Yes, but the OP's location appears to be 'Scotland'. Quite a big place!

[Roxylass]

When I say red probe on to it I mean the red probe on the male connector on the back of the alternator.

[Roxylass]

I shall try again tomorrow the proper way.

Should have given it more thought.

[Tony Brooks]

When I say red probe on to it I mean the red probe on the male connector on the back of the alternator.

 

Which implies that you took the female blade off the male connector. If you did that with the engine stationary and then started the engine then there is every chance no damage has been done but if you broke the connection with the alternator charging damage may have been done.

 

 

Yes, but the OP's location appears to be 'Scotland'. Quite a big place!

 

Yes, and probably not so many members up there. He could keep his boat on the English northern waterways but I rather doubt it so almost certainly he is on the Forth - Clyde canal system so maybe not such a large area.

[Roxylass]

Put the voltmeter on the thick cable took a bit of tape of to expose the copper

Black probe on the alternator getting a reading of 14.52v

Oil pressure between 38-40.

[Tony Brooks]

So it seems the alternator is working although 14.5 on a single alternator engine immediately after a start seems just a little high to me. Now we need to find out why the warning lamp is not going out although I think, as do others, that with the drive from the camshaft the most likely explanation for now is lack of speed. Bizzards "fix" of a higher wattage warning lamp bulb might well overcome the problem.

 

SirN asked about the voltage on the warning lamp terminal. I would ask for it with the ignition on and engine stationary and again when the engine is charging. The first would give us an idea if the brushes are making a poor contact while the second will give an idea about the field diodes.

 

 

 

 

[Mikexx]

Put the voltmeter on the thick cable took a bit of tape of to expose the copper

Black probe on the alternator getting a reading of 14.52v

Oil pressure between 38-40.

 

Brill, that suggests the alternator is working as expected.

 

You mentioned a previous battery voltage was was measure at 13.60, was this on the AC setting?

 

When running, now measure between the alternator body and the battery -ve and report what voltage you get?

 

Also when running measure between the alternator output and the battery +ve.

 

If both of these measurements are near 0v and both alternator and battery volts are around 14.5V, apart from the exciter switch all seems to be working fine and your starter battery is being topped up after a start. Personally I would then leave all alone.

[Roxylass]

The 13.60 was the reading taken from the battery posts before i started the engine

And the voltmeter was set at DC-20

How do I measure between the alternator body and the battery also

How would I measure between the alternator output and the battery

Apologies for being a bit thick

[Roxylass]

So it seems the alternator is working although 14.5 on a single alternator engine immediately after a start seems just a little high to me. Now we need to find out why the warning lamp is not going out although I think, as do others, that with the drive from the camshaft the most likely explanation for now is lack of speed. Bizzards "fix" of a higher wattage warning lamp bulb might well overcome the problem.

 

SirN asked about the voltage on the warning lamp terminal. I would ask for it with the ignition on and engine stationary and again when the engine is charging. The first would give us an idea if the brushes are making a poor contact while the second will give an idea about the field diodes.

 

If you let me know how to do this I certainly shall.

[Mikexx]

The 13.60 was the reading taken from the battery posts before i started the engine

And the voltmeter was set at DC-20

How do I measure between the alternator body and the battery also

How would I measure between the alternator output and the battery

Apologies for being a bit thick

 

No need to apologise.

 

With meter on DC20:

1 Place black probe on battery -ve terminal, red probe on the alternator metal casing

2 Place black probe on battery +ve terminal, red probe on the alternator output stud (heavy red wire)

3 Place black probe on alternator body and red read on alternator output stud (heavy red wire)

4 Place black probe on batter -ve terminal, red probe on battery +ve terminal.

 

I know you have made some of these measurements before, but if these can be made quickly one after the other it would place more value on the other measurements.

 

Can you also note if you get a negative reading, you should on (1)?

[Roxylass]

Get the readings tomorrow after work.

[Roxylass]

Black probe on battery negative red probe on alternator case 0.15

Black probe on battery positive red probe on heavy copper cable 0.7

Black probe on alternator case red probe on heavy copper cable 14.50

Black probe on battery negative red probe on battery positive 14.37

Didn't see a negative reading

For sir nibbles

Red probe on warning light terminal black probe on alternator case 14.50

No reading on this with just the ignition on

[Sir Nibble]

The alternator is healthy. You have more voltage drop than is healthy. Only thing I can think of to explain your symptoms is the failure of a parallel warning light resistor. Have you trust a bigger bulb yet?

[bizzard]

The alternator is healthy. You have more voltage drop than is healthy. Only thing I can think of to explain your symptoms is the failure of a parallel warning light resistor. Have you trust a bigger bulb yet?

There's also a suddenly swollen drive pulley to try too.

[Mikexx]

The alternator is healthy. You have more voltage drop than is healthy. Only thing I can think of to explain your symptoms is the failure of a parallel warning light resistor. Have you trust a bigger bulb yet?

 

The readings don't really add up, literally. I could also assume the battery at 14.37, just 0.13V less than the alternator is also correct.

 

One thing about cheap DVMs is they are sometimes upset by an AC waveform on top of a DC waveform such that I might not trust 100% the direct alternator measurement. I can't quite make out the DVM name in one of the pictures, either way it doesn't look familiar.

 

In the very first photo in this topic, the alternator power cable has a section covered with insulating tape. One wonders what's below that! The 0.7V is worryingly high, but the 0.15V is the wrong polarity.

 

Are you suggesting the original fault could have been caused by a failure of an unknown parallel resistor? I suppose coincidences do happen!

 

I'm not sure if we have moved forward, apart from ascertaining the battery seems to be charged sufficiently, and the exciter switch is doing its job.

 

Without applying a serious load to the battery whilst the alternator is producing an output I can't see us moving forward. There isn't a second alternator on the engine so I'm also wondering what Roxylass does for power?

[bizzard]

 

The readings don't really add up, literally. I could also assume the battery at 14.37, just 0.13V less than the alternator is also correct.

 

One thing about cheap DVMs is they are sometimes upset by an AC waveform on top of a DC waveform such that I might not trust 100% the direct alternator measurement. I can't quite make out the DVM name in one of the pictures, either way it doesn't look familiar.

 

In the very first photo in this topic, the alternator power cable has a section covered with insulating tape. One wonders what's below that! The 0.7V is worryingly high, but the 0.15V is the wrong polarity.

 

Are you suggesting the original fault could have been caused by a failure of an unknown parallel resistor? I suppose coincidences do happen!

 

I'm not sure if we have moved forward, apart from ascertaining the battery seems to be charged sufficiently, and the exciter switch is doing its job.

 

Without applying a serious load to the battery whilst the alternator is producing an output I can't see us moving forward. There isn't a second alternator on the engine so I'm also wondering what Roxylass does for power?

I should imagine that the boat is possibly something like an open fishing boat with just a battery for engine starting and perhaps horn bilge pump and nav lights. It might have a split charge relay to charge another battery although there's been no mention of one. If the boat is used on open waters and not canals as such, the engine would most likely be run much nearer its full revs, perhaps against wind, tides, currents, so once the charge has been excited the probable higher revs won't be so critical with using the small diameter drive pulley.

[Sir Nibble]

The readings don't really add up, literally. I could also assume the battery at 14.37, just 0.13V less than the alternator is also correct.

 

One thing about cheap DVMs is they are sometimes upset by an AC waveform on top of a DC waveform such that I might not trust 100% the direct alternator measurement. I can't quite make out the DVM name in one of the pictures, either way it doesn't look familiar.

 

In the very first photo in this topic, the alternator power cable has a section covered with insulating tape. One wonders what's below that! The 0.7V is worryingly high, but the 0.15V is the wrong polarity.

 

Are you suggesting the original fault could have been caused by a failure of an unknown parallel resistor? I suppose coincidences do happen!

 

I'm not sure if we have moved forward, apart from ascertaining the battery seems to be charged sufficiently, and the exciter switch is doing its job.

 

Without applying a serious load to the battery whilst the alternator is producing an output I can't see us moving forward. There isn't a second alternator on the engine so I'm also wondering what

Roxylass does for power?

I am suggesting that getting the same voltage from B+ and D+ the diodes are ok. Since the reported voltage is in the right ball park to also be correct and regulators fail open circuit or short circuit rather than changing its set point that's ok too. The alternator is healthy.

Most likely more revs would sort the problem but that's not currently available. I am suggesting that the bloke who installed the system included a parallel resistance to compensate. CAV used to supply a bulb holder with a resistance winding around it. I would check with a test lamp and look at changing the pulley, or more likely (because I can do it for free) reconfigure the alternator winding for slow speed.

[MtB]

I am suggesting that getting the same voltage from B+ and D+ the diodes are ok. Since the reported voltage is in the right ball park to also be correct and regulators fail open circuit or short circuit rather than changing its set point that's ok too. The alternator is healthy.

Most likely more revs would sort the problem but that's not currently available. I am suggesting that the bloke who installed the system included a parallel resistance to compensate. CAV used to supply a bulb holder with a resistance winding around it. I would check with a test lamp and look at changing the pulley, or more likely (because I can do it for free) reconfigure the alternator winding for slow speed.

 

 

That's a new one I've not heard before!

 

Can any alternator be reconfigured for 'slow speed' Mr Snibs?

 

How slow? Depending on the answer this sounds like the correct fix for everyone with a half-speed pulley SR2...

[Mikexx]

........ more likely (because I can do it for free) reconfigure the alternator winding for slow speed.

 

The alternator looks as if it is a Lucas style which would I would expect to already have a stator in a star 'Y' for max voltage. If it's currently a delta winding then yes I can see how you can improve voltage output when changed to a star.

 

The rotor would normally be close to, or in, saturation so any increase in magnetic flux from an increase in magnetic field (NI) would be minimal.

 

What sort of reconfiguring did you have in mind?

[Sir Nibble]

Delta to star. Done it before with an A127 and cut in speed reduces dramatically. Max current is of course reduced by the same factor. (root 3).

[Roxylass]

Going to renew the battery lead to the alternator this weekend.

The battery says 140 ah on it what size mm thickness cable would I need

Also can I get spade connectors that size

And yes it is an open boat ex roysth dockyard

I use it for lobster potting.

[MtB]

Delta to star. Done it before with an A127 and cut in speed reduces dramatically. Max current is of course reduced by the same factor. (root 3).

 

 

Ah fascinating, thanks!

 

Do you mean max current it reduced by the cubed root of three? 1.44 (approx)? This intuitively seems likely, or the square root 1.73 (approx)?

 

Either way it would seem a worthwhile modification.

[Sir Nibble]

Square root. Root 3 is the magic number for 3phase. If I recall, cut in was about 500 and 45A max at about 1200. All alternator rpm from a nominally 65A stator.

[MtB]

I'm surprised no-one suggested this mod for the female boater in that long long thread a couple of years ago who was totally unwilling to cut the necessary hole in here bulkhead to fit a bigger camshaft pulley.

 

Or maybe they did, and she rejected that idea too!