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Lucas Prince of Darkness


zenataomm

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So here's a conunderumnum for the collective.

The background …

Lister SR2 fitted with one of those old Lucas 3 prong alternators. When I fitted the alternator a year ago to replace a similar one I noticed that it needed to be revved quite high to extinguish the red light.

Recently while returning to the mooring I throttled back to tick over to negotiate a ninety degree turn. The red charging light came on, and then wouldn't go out. It mattered not a whit how much I revved the engine or which trousers I wore, the light stayed on.

Having descended into the engine room I noticed that the alternator wasn't sitting in line anymore, it seemed to have twisted a tad in its cradle.

So over the last few weeks I have: -

 

Rebuilt the frame the alternator sits in – No change

Ensured belt is straight and tight – No change

Had the alternator bench tested it works perfectly and chucks out 20 amp (about right, and all I need) -No change

Checked voltage at several points - Nothing higher than 12V

Removed all crimp terminals, cleaned surfaces and replaced terminals with soldered ones – No change

Fully charged both batteries and cleaned all terminals – No change

Meter tested for continuity and for 12 volt input – No change

Threw my tools around and snarled at happy people – No change

Fitted a direct earth from the alternator bracket to the negative battery terminal – No change

 

So I've come away for a few days rest as there's only so much fun one can have.

I've come to the conclusion …

1) Somebody has unfairly changed the laws of physics without telling me.

OR …

b) I need to totally rewire the whole boat plus the boats either side of me with the best tinsel I can shoplift.

ALTERNATIVELY …

*The dopey little bulb in the telltale isn't drawing enough amps to excite the field.

 

Personally I reckon it's number b) but when I go back next week I shall try wiring in another warning light in parallel with the original as it's easier than the other two.

 

Who reckons which?

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26 minutes ago, zenataomm said:

Who reckons which?

 

None of the above. 

 

One of your diodes has failed and your alternator is running on only two cylinders.

 

It should be poking out 14.4+v.

 

 

(Not the 12v you mention.)

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4 minutes ago, bizzard said:

On an SR it should be camshaft driven. Do you have the the large diameter pulley fitted ie 9, 10 or 12''.

 

Can't be the problem, or it would never have worked....

 

Well not the main problem anyway!

 

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1 minute ago, Mike the Boilerman said:

 

Can't be the problem, or it would never have worked....

 

Well not the main problem anyway!

 

It would have worked with the small pulley if revved up enough.

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2 minutes ago, Mike the Boilerman said:

 

Yes it used to work, but now it doesn't. 

 

So summink broked. Obvs....

Yes I agree. Those old ACR alternators are cheap as chips for a rebuilt one. And probably upgrade the warning light bulb to 2 to 5 W will put the light out quicker whichever pulley its got.

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43 minutes ago, Mike the Boilerman said:

 

None of the above. 

 

One of your diodes has failed and your alternator is running on only two cylinders.

 

It should be poking out 14.4+v.

 

 

(Not the 12v you mention.)/////////

 

I'll try explaining while standing differently.

Although it works on the bench tester, and I have done everything I detailed, it doesn't work in the boat. It's output is Zilch, nada, nowt!

On the bench test it chucked out 20 amps

The 12 v I recorded was only the charge stored in the batteries, I guess.

An induction ammeter showed no charge with the engine running, indicating (to me) nothing is coming out of the alternator or being put back into the batteries.

43 minutes ago, bizzard said:

On an SR it should be camshaft driven. Do you have the the large diameter pulley fitted ie 9, 10 or 12''.

You're right, and it is a large pulley.

 

Hence my suspicion the laws of physics have altered.

Decimalisation has caught up with us.

God knows what will happen after Brexit

  • Greenie 1
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You say it works on the bench but don’t specify at what rpm. Perhaps when spun at near light speed it does work, but wouldn’t work if it were spun by the engine going at a mere 5000rpm (just before the pistons departed into space).

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4 hours ago, Tony Brooks said:

Don't suppose its an old 10AC or 11AC with external regulator and in some cases warning lamp control?

Excellent point, but it was working for over 6 months before this.

 

4 hours ago, nicknorman said:

You say it works on the bench but don’t specify at what rpm. Perhaps when spun at near light speed it does work, but wouldn’t work if it were spun by the engine going at a mere 5000rpm (just before the pistons departed into space).

I don't know the rpm on the bench tester, but he did say something about putting on a good load.  Which on after thought I took to mean the piddly light bulb?

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Checked engine earth? Is it hand start?

 

Remove the wire off the D+, little spade connection.

Take a bit of wire from the D+ to a bulb, 5 or 6 watts or bigger, and from the other side of the bulb direct onto the battery + terminal ( assuming the battery is - earthed )

Start engine.

Now does it work?

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On ‎26‎/‎05‎/‎2019 at 13:46, hider said:

Checked engine earth? Is it hand start?

 

Remove the wire off the D+, little spade connection.

Take a bit of wire from the D+ to a bulb, 5 or 6 watts or bigger, and from the other side of the bulb direct onto the battery + terminal ( assuming the battery is - earthed )

Start engine.

Now does it work?

Thanks for that one, I'll try it tomorrow when I get down there.

I shall report back and bore you all to tears or worse upon my return.

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I would be checking the regulator unit, I had one on an older rangerover that decided 8v was a fully charged battery from time to time.

to start with it wasn't a problem as it only did it for a couple of minutes for every hour of running, but eventually the ratio reversed so it was hardly ever kicking in properly.

 

I ended up pulling the regulator off a different alternator and making a frankenalternator which despite looking wrong worked without fault for the next 10 years that I ran the vehicle

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The coroner's report is back.

Wiring another ignition lamp in parallel with the original was what was needed.

 

The extra draw was enough to kick it into life, both bulbs extinguish, my drop meter/alternator tester shows just under 15 volt input.

:clapping:

So the good news is that the laws of physics remain as were and nor do I have to rewire throughout.

Although I do recommend not trusting those crimp connectors without soldering them as well.  Years ago I bought a butane soldering iron which finally proved its worth.

 

It just goes to show how much can go taters with an alternator.

Thanks for all the advice and support, if you also suspected the load on the winding circuit then award yourself 8 points and a quick "Woo-Hoo" 

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59 minutes ago, zenataomm said:

Although I do recommend not trusting those crimp connectors without soldering them as well. 

If you use the correct size crimp and a proper ratchet crimp tool they will make a solid, reliable and secure connection. Soldering makes them susceptible to vibration. You won’t find any soldered joints on an aircraft but you’ll find very many crimps. 

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Thanks for the amusing - for us sat on the sidelines that is - original post.

 

There is another thread running called "some days the Gods are against you"... I find that on a boat pretty much every job they are against you. No wonder old sailors were so superstitious.

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7 hours ago, Paringa said:

Thanks for the amusing - for us sat on the sidelines that is - original post.

 

There is another thread running called "some days the Gods are against you"... I find that on a boat pretty much every job they are against you. No wonder old sailors were so superstitious.

Are you suggesting my lunch of Albatross and chips might be at the bottom of all this?

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