adrianreeve
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| posted on 6/3/12 at 04:33 PM |
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Alternator not charging?
I have a Lucas alternator in my haynes roadster. I've recently started the engine for the first time, and I don't think the alternator is
charging.
Am I right in thinking that with an older style Lucas alternator with 3 terminals, the 2 big ones are identical, so only one of them needs connecting,
and the small one goes to the charge light on the dash. presumably, the unit is then earthed through the chassis where it mounts?
Should the large terminal connection go straight to the battery?
With the engine running, if I put the multimeter over the battery terminal, I get 12.29v at the moment, and I would expect to see at least 13v, rising
with revs.
Any advice welcome as always!
Cheers
Adrian
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owelly
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| posted on 6/3/12 at 04:52 PM |
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Does the charge light come on with the ign and then go out with engine running?
http://www.ppcmag.co.uk
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mark chandler
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| posted on 6/3/12 at 05:00 PM |
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Yes, your assumption on wiring is correct, the fat red usually goes to the starter motor feed if on that side of the engine.
It should rise to 13.8v once the field coils are energised; it could something as simple as be the alternator warning light bulb blown as this is a
switched power via the bulb that energises the field coils.
When running it sends voltage back up the wire so the bulb extinguishes as 13v both sides.
Regards Mark
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adrianreeve
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| posted on 6/3/12 at 05:38 PM |
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I'm using an led warning light as part of a set, would it still work ok?
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britishtrident
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| posted on 6/3/12 at 05:43 PM |
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12.9v is a little above normal battery voltage at current ambient temperatures.
What is the battery voltage with the ignition off ? and with the ignition on but engine not running ?
It could just be a simple brush or regulator problem or less likely a diode pack or slip ring problem.
Normal voltage output above idle speed varies depending on the rated output generally it should be in the range 13.4 to 14.9 --- never above 15v
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Lucas 3 terminal alternators come in two main variety the ACR series which have a large black rear cover and the later A127 series (aka Lucas
Magnetti Marelli ) which have the regulator and brush assembly in a single metal pack held on to the back of the alternator by two nuts.
Both types are very easy to overhaul, the A127 brush and regulator box can be replaced on car by simply undoing two nuts.
[Edited on 6/3/12 by britishtrident]
[Edited on 6/3/12 by britishtrident]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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omega 24 v6
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| posted on 6/3/12 at 05:47 PM |
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No
The warning light will need to be a 3 watt bulb. You could wire it in, as well as an led, and hide it, but the led only is your problem.,
If it looks wrong it probably is wrong.
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britishtrident
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| posted on 6/3/12 at 05:50 PM |
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quote:
Originally posted by adrianreeve
I'm using an led warning light as part of a set, would it still work ok?
That explains it the warning light supplies the field exciting voltage to kick start the charging it has to be a bulb or led in parallel with
ballast resistor.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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adrianreeve
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| posted on 6/3/12 at 05:55 PM |
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That's pants then, it's sold as part of a set of 6 from CBS, which are all now mounted in my dash, see below
Cheers
Adrian
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omega 24 v6
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| posted on 6/3/12 at 06:24 PM |
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Just add in the hidden bulb and its done. Many of us have it like that
If it looks wrong it probably is wrong.
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adrianreeve
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| posted on 6/3/12 at 06:47 PM |
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Thanks gents
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matt_gsxr
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| posted on 6/3/12 at 07:54 PM |
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If you don't like the idea of a bulb then you could use the equivalent resistor. A resistor will never fail which would be an advantage.
I think 50 Ohm, 5 Watt would do it.
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snowy2
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| posted on 6/3/12 at 08:18 PM |
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i use a led battery light on my lucas alternator and it has worked fine for 4 years and 20,000 miles no problem......
sometimes you are the pigeon, most of the time the statue.
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