GL: MEASURING AMPS

[Jim Healy]

David and others, 
 
Sears has a auto-ranging, handheld, clamp-on meter that measures both AC and
DC amps (and voltages, hertz, ohms, temperature).  The Sears model number is
82369, it's about $60.00, and it has two DC amp scales: 0-40 and 0-400.
It's an excellent little tool, and much less money than Fluke or other DC
clamp-on's that I've seen.  Over the last couple of years, I have found this
to be a very valuable little tool on the boat.  Sears also has a small
handheld infrared thermometer, for about $80.  Also invaluable around the
boat!
 
No personal connection to Sears; just very happy with their meter/tools.
 
Sue, 
 
As others have already pointed out, you cannot proceed with electrical
diagnosis unless the device is correctly mounted mechanically, tight belts,
etc.  If the belts seem loose (TEST WITH ENGINE NOT RUNNING) (they should be
quite tight) or if there's a black powdery residue around the pulleys that
the belts run on, have that fixed first.
 
Did you have the alternator replaced by a professional electrical guy, or
was it a DIY job?  If it was done by a professional marine electrician,
things like wire sizes SHOULD be OK.  The manuals for the alternator will
tell you what you should have, and it should be easy to check in a new,
physically clean installation.  CHECK WITH ENGINE NOT RUNNING.  If the
install was a DIY job, CHECK EVERYTHING!  It could be perfect, but it could
be flawed, too.  
 
If you aren't VERY comfortable with electrical concepts, get Nigel Caulder's
book, "Boatowner's Electrical and Mechanical Handbook," and thoroughly
understand both what you're going to do and how to do it before you tinker
with the alternator, the test done with the engine running, or other parts
of the charging system.  It's easy to accidentally damage things here, and
the batteries contain enough stored energy to start a serious fire and
worse.  
 
If you are hooked up to shore power, make sure to shut off/otherwise
disconnect any AC battery charger(s) in the charging system while you're
investigating the engine alternator's operation and output.  If the AC
charger is also running, it can give you false indications of what's
happening in the rest of the system, as well as sparks and arcs at the most
inappropriate times.
 
It is NOT wise (a BAD idea) to run the alternator without it's output being
hooked up to a battery, and certainly, DO NOT disconnect it from the battery
bank when it is running.  If you do, you can inadvertently blow the diode
trio pack in the alternator, causing a expensive trip to an alternator
re-builder and a voided manufacturer's warrantee,  
 
Some of the new external voltage regulators have temperature sensors that
attach to the alternator and to batteries.  Their purpose is to monitor
operating temperatures and reduce the alternator's output drive when the
alternator gets too hot or if the battery pack gets too warm.  Alternators
get very hot very quickly when they first come on, because that's when the
batteries are down, and require their fastest bulk charge rates.  By the
time you get from the starter switch to the engine room, the alternator is
already way too hot to touch by hand.  The alternator gets too hot to touch
when it's operating normally, so use an infrared thermometer to test the
temperature, make sure you STAY WELL CLEAR of any engine belts, and use the
manufacturer's manual to determine "normal" alternator temps.  Some
regulators can display these temperatures, too.  The manuals that come with
these alternator/regulators kits will tell you how to interpret the
regulator display, and what the set temps are.  
 
If all this sounds too complicated for you, then my advice is to get a
qualified marine electrician to check it out for you.  There is a lot to
consider, some tests require working around a running engine, and there are
some serious risks to be avoided.  
 
Jim
 
Peg and Jim Healy aboard Sanctuary,
currently at Rock Creek, Pasadena, MD
AGLCA # 3767
MTOA # 3436