At 10:12 AM 7/5/2004 -0400, Alan.McEachran@anixter.com wrote:
>My 78 Spitfire with the Lucas alternator has totally failed to keep my
>battery charged. I had a "no start" fail the other dya with no lights left
>on from the previous ride. She has never had any such issues in the past 4
>years that I have owned her. Now, when boosted and running, the engine
>ticks over just fine, but turn signals, headlights, virtually all
>electricals are literally dim.
>
>I suspect the alternator as my problem. My Haynes says I can do a rough
>check on it by connecting an Ampmeter in series between the brown wire from
>the alternator and the starter. I'm no electrical whiz, but I do have a
>nice Fluke Digital Multimeter that I'm sure I could fry if I fought the
>need for advice.
>
>Assume that I have never seen either an alternator or a multimeter before.
>Does anyone have a procedure for dummies I could follow?
Alan,
Yes, you will probably fry the Fluke multimeter.
A quick test to check an alternator or generator is:
1. Set the multimeter to read about 15 V. What ever scale that is.
2. With the enging NOT running and all electrical off, put the Pos. lead
from the meter to the Positive (+) terminal of the battery, and the
Neg. lead from the meter to the Neg. (-) terminal of the battery. The
meter should read very close to 12.0V.
3. Now start the engine, let it idle. Check the voltage at the battery
again (as above). If the idle is below 1,000 rpm, the meter should still
read about 12.0V.
4. Now speed the engine up to about 1,500 rpm. The voltage on the meter
should go up to between 13.5 and 14.7 V. If so, then the alternator
is putting out.
This is a lot safer than trying to measure the current. The old lucas
generators output about 25A and the alternators can output about 50+
amps. But this depends on the draw - how much electrical devices are on.
To measure that much current, you usually use a clip on amp meter so the
current isn't flowing through the meter, unless you have an amp meter
in the car.
You might want to check out my electrical primer series on my Morgan
web page. The 1st article is "Electrical Primer - Introduction to
Electricity" - http://www.team.net/www/morgan/tech/art016.html
Hope this helps.
John
John T. Blair WA4OHZ email: jblair1948@cox.net
Va. Beach, Va (eBay id: zebra48-1)
Phone: (757) 495-8229
48 TR1800 48 #4 Midget 65 Morgan 4/4 Series V (B1109)
75 Bricklin SV1 (#0887) 77 Spitfire 71 Saab Sonett III
65 Rambler Classic
Morgan: www.team.net/www/morgan
Bricklin: www.bricklin.org
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