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Chris Miller
Grand Master
Username: cjm51213

Post Number: 409
Registered: 5-2013
Posted on Thursday, 23 June, 2016 - 07:44 am:   Edit PostDelete PostView Post/Check IP

Hi Folks,

I have suspected for some time that my alternator was not up to snuff and this morning, on a whim, I stopped into Napa and they confirmed my suspicion. I don't think it is completely dead, but I think it is only generating about 12 volts, where it should be generating 15-ish.

So, this raises some questions.

Is this a GM alternator, maybe with a contemporary part number?
Does anybody have an application cross-reference for a contemporary alternator?

Is there any advice available for rebuilding an alternator? If the bearings are still good, and I suspect that they are, it is brushes and diodes, but that raises the issue of parts. Anybody have any leads?

Brian: I looked through my copy of your Resources guide before I asked the question, so I am trainable. (-:

Chris.
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Bob Reynolds
Grand Master
Username: bobreynolds

Post Number: 404
Registered: 8-2012
Posted on Thursday, 23 June, 2016 - 08:02 am:   Edit PostDelete PostView Post/Check IP

It might not be the alternator, it might be the control box. This adjusts the output voltage from the alternator with respect to electrical load, battery voltage, etc.

Bob UK is the expert on this, as he always used to be on about adjusting the output voltage. You might find some useful information in his posts.
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Chris Miller
Grand Master
Username: cjm51213

Post Number: 410
Registered: 5-2013
Posted on Thursday, 23 June, 2016 - 08:05 am:   Edit PostDelete PostView Post/Check IP

Hi Bob,

Where do I find the control box? It seems to be worth investigating...

Thanks for the help,

Chris.
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gordon le feuvre
Prolific User
Username: triumph

Post Number: 122
Registered: 7-2012
Posted on Thursday, 23 June, 2016 - 09:05 am:   Edit PostDelete PostView Post/Check IP

Chassis no. would help, but control box usually CAV aluminium in colour standing vertically bolted in front of o/s heater blower motor under bonnet(hood)
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Jeff McCarthy
Grand Master
Username: jefmac2003

Post Number: 456
Registered: 5-2007
Posted on Thursday, 23 June, 2016 - 09:17 am:   Edit PostDelete PostView Post/Check IP

Located on the right side bulkhead, as Gordon says, near the blower motor.
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Jeff McCarthy
Grand Master
Username: jefmac2003

Post Number: 457
Registered: 5-2007
Posted on Thursday, 23 June, 2016 - 09:23 am:   Edit PostDelete PostView Post/Check IP

These are not hard to find. Shop around - some online stores charge much more than others. Take a photo of your one to get an exact match. This is a part I recommend everyone keep as a spare in the boot. It is, for our cars, an unusually quick plug and play fix if it fails.
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David Gore
Moderator
Username: david_gore

Post Number: 2086
Registered: 4-2003
Posted on Thursday, 23 June, 2016 - 09:27 am:   Edit PostDelete PostView Post/Check IP

Chris,

the alternator on DRH14434 was a CAV heavy duty alternator.

Any auto electrician should be able to rebuild whatever alternator is fitted to your vehicle. If the regulator is faulty, replacement clones of the original Lucas unit are available.
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Chris Miller
Grand Master
Username: cjm51213

Post Number: 411
Registered: 5-2013
Posted on Thursday, 23 June, 2016 - 09:30 am:   Edit PostDelete PostView Post/Check IP

Hi Jeff,

I suspected that was the part. I can hear it click when I press the horn button. Is it adjustable or simply replaceable? How do I test this thing? It may be the problem or it might be good and the alternator is the problem.

Is this a GM or Lucus alternator?

Thanks for the help,

Chris.
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Chris Miller
Grand Master
Username: cjm51213

Post Number: 412
Registered: 5-2013
Posted on Thursday, 23 June, 2016 - 09:55 am:   Edit PostDelete PostView Post/Check IP

So, this is twice I've encountered "CAV" and I don't know what it means. Or at least I don't recognize it.
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Patrick Ryan
Prolific User
Username: patrick_r

Post Number: 271
Registered: 4-2016
Posted on Thursday, 23 June, 2016 - 10:04 am:   Edit PostDelete PostView Post/Check IP

According to the net CAV was an electrical pioneering company formed by Charles Anthony Vandervell. Many firsts were achieved by this company, so it seems Lucas saw the value in it to further their needs so Lucas purchased CAV in 1926
https://en.wikipedia.org/wiki/Lucas_Industries#CAV
Very interesting reading not just about CAV, but Lucas as well.
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Patrick Ryan
Prolific User
Username: patrick_r

Post Number: 272
Registered: 4-2016
Posted on Thursday, 23 June, 2016 - 10:13 am:   Edit PostDelete PostView Post/Check IP

Wish my engine bay looked like that Jeff.
I somehow need to clean mine before the next Concours as it was noted as being "a bit dirty" at the last one.
But a LONG time car and truck mechanic here in Oz, all of our old cars and trucks were Lucas equipped and I know never to mix Lucas with water.
But I am really struggling to know what to do here.
Anyway.
Awesome engine bay mate.
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Jeff McCarthy
Grand Master
Username: jefmac2003

Post Number: 458
Registered: 5-2007
Posted on Thursday, 23 June, 2016 - 10:21 am:   Edit PostDelete PostView Post/Check IP

Ah Patrick, if only it were mine! I collect photos of parts and details of our cars for reference purposes. I've currently got a flooded carburettor and a report of the dreaded sludge leaking from my rocker cover - detailing my engine bay is on the list, but nowhere near the top of it yet...
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Patrick Ryan
Prolific User
Username: patrick_r

Post Number: 274
Registered: 4-2016
Posted on Thursday, 23 June, 2016 - 12:54 pm:   Edit PostDelete PostView Post/Check IP

If you weren't so far away Jeff we could get together for a good clean!
Bugger, I hope you can sort it out soon mate.
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Chris Miller
Grand Master
Username: cjm51213

Post Number: 413
Registered: 5-2013
Posted on Friday, 24 June, 2016 - 02:52 am:   Edit PostDelete PostView Post/Check IP

Hi Folks,

So the brand is probably CAV. That helps. I'll look for marks and see if I can determine the model.

I still don't know how to determine if my problem is the voltage regulator or the alternator proper. Is there a diagnostic to tell me?

Assuming it is the voltage regulator, is the voltage regulator something I can repair or is it only replaceable, like a light bulb? Is there a specification, like an electrical diagram of this thing, so I know how it works, if I have to consider a contemporary replacement?

Assuming it is the alternator proper, the parts in question are the brushes and the diodes. Does anybody have a source for brushes and diodes?

Thanks for the help,

Chris.
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Omar M. Shams
Grand Master
Username: omar

Post Number: 703
Registered: 4-2009
Posted on Friday, 24 June, 2016 - 05:25 am:   Edit PostDelete PostView Post/Check IP

The chances are much higher that your problem is the regulator box and not the alternator.
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Chris Miller
Grand Master
Username: cjm51213

Post Number: 414
Registered: 5-2013
Posted on Friday, 24 June, 2016 - 06:06 am:   Edit PostDelete PostView Post/Check IP

Hi Omar,

I am inclined to agree, but I sure would like a dispositive test. For example, can I measure the voltage at the alternator if it is completely disconnected, meaning is the regulator necessary for the alternator to function in any capacity, or is it simply a mechanism to shut the alternator off to prevent engine drains?

I think this divides my problem. Either I am getting acceptable voltage at the alternator, or I am not. What would be the expected voltage reading at the alternator terminals? There is the concomitant problem that I may not be producing enough juice to maintain that voltage in the face of existing demands, but if I can measure volts at the alternator terminals, I should be able to measure amps. So, what would be the expected reading for amps at the alternator terminals?

Thanks for the help,

Chris.
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Jean-christophe Jost
Experienced User
Username: jc_jost

Post Number: 21
Registered: 3-2016
Posted on Friday, 24 June, 2016 - 06:55 am:   Edit PostDelete PostView Post/Check IP

Chris,

I think this thread is a reference
http://au.rrforums.net/forum/messages/17001/16889.html

and there is also a diagam of the regulator in Tee One Topics issue 51.

Best regards
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Geoff Wootton
Grand Master
Username: dounraey

Post Number: 1295
Registered: 5-2012
Posted on Friday, 24 June, 2016 - 07:51 am:   Edit PostDelete PostView Post/Check IP

Chris

Can't you get a free test at one of your local motor factors like Autozone, O'reillys or Pep-boys. I've just picked this up off Google:

"AutoZone will test your car's parts for free. We can test your car's battery, alternator, starter and voltage regulator while they're still on your car. We can also give your car a complete starting and charging systems test."

Geoff
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Jeff Young
Prolific User
Username: jeyjey

Post Number: 262
Registered: 10-2010
Posted on Friday, 24 June, 2016 - 08:38 am:   Edit PostDelete PostView Post/Check IP

The regulator is needed for the alternator to function at all. It controls the current in the rotor field, which in turn controls the output voltage.

But yeah, it should be pretty easy to get it tested....

Cheers,
Jeff.
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Jim Walters
Frequent User
Username: jim_walters

Post Number: 88
Registered: 1-2014
Posted on Friday, 24 June, 2016 - 04:41 pm:   Edit PostDelete PostView Post/Check IP

There is a symptom that helps diagnose alternator problems. If you hear a high pitch whine (fairly faint but audible) in your radio speakers (when the radio is on) that corresponds to engine RPM's it is symptomatic of a bad diode in the alternator. You can easily test whether the alternator or voltage regulator is faulty by following the instructions on page M25 & 26 here: http://rrtechnical.info/sy/tsd2476/13.pdf Parts for these should be available at any automotive electrical rebuilder.

SRC18015 SRE22493 NAC-05370
www.bristolmotors.com
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Chris Miller
Grand Master
Username: cjm51213

Post Number: 415
Registered: 5-2013
Posted on Saturday, 25 June, 2016 - 02:56 am:   Edit PostDelete PostView Post/Check IP

@Jean-christophe: Thanks for the reference. That is quite helpful.

@Geoff: I can get a test and I did, but the test is binary -- "Works" or "Doesn't work". My test showed "doesn't work", but my experience show that it mostly works. And the test doesn't explain what is wrong, meaning regulator, alternator diodes, alternator brushes, or anything else that I might not understand.

@Jim Walters: I've been reading that section. And each time I read it I understand better what I should do. I understand more now than I did last week partly because everyone has been so helpful with my education.

The regulator is non-serviceable so I think I have a line on a replacement. I will probably want that even if the one I have is fine. I like to have spares. Swapping the regulator is a pretty easy diagnostic, assuming the new one is working correctly, and with the Tee One topic issue 51 diagram, I should be able to perform some minimal integrity tests.

Thanks for the help,

Chris.
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John Kilkenny
Prolific User
Username: john_kilkenny

Post Number: 242
Registered: 6-2005
Posted on Saturday, 25 June, 2016 - 10:33 am:   Edit PostDelete PostView Post/Check IP

Chris,
There are three unknowns in this equation, the alternator, the CAV voltage control and the battery. Any one can be the problem.
Firstly the voltage control. If the ignition light comes on when the ignition is switched on and goes out when the engine starts it is unlikely the control is faulty. There are three control inputs marked H (High), M (Medium) and L (Low) corresponding to the expected load on the battery. These affect the alternator voltage output. See which one is selected.
For a quick check of the alternator, with the engine on fast idle, switch on the headlights and check the voltage at the battery positive terminal with a voltmeter. If it's over 13.5 it's probably OK.
Finally the battery, how old is it ? Does it hold a charge when the car is not used for a couple of weeks ? Maybe it's time for a new one.

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