changes in the area you are working in.
The trick is to look for abnormalities.)- If there is no current flow, there will be no
temperature change. The circuit in ques-
tion needs to at least be trying to work for
the heat gun to acquire any relevant tem-
perature readings.
It’s best to use the gun after everything has
been shut down for a bit, and the ambient
temperature has stabilized throughout what-
ever system you are checking. The reason is
that after a system has been in use for a time,
thermal transfer from one part to another has
occurred (i.e., the temperature has risen in the
space), and the pronounced temperature dif-
ferential you are looking for will be much
harder to find. Copper wire is not only a good
conductor of electricity, it’s also a great con-
ductor of heat. (In fact, it can act as sort of a
heat sink for whatever it’s attached to.) If a
component and its wire are at the ambient
temperature, and the connection is loose, then
almost immediately after you turn on the
device, you’ll see a marked increase over ambi-
ent temperature at the connection.
I have found that the best way to use a heat
gun is to first scan the area where you will be
working to determine the average ambient
temperature. This is your benchmark. Then,
when you scan a specific termination or device
and find a much higher temperature (e.g.,
25°F higher), you will know you’ve discovered
a potential problem.
Let’s look at a common real-world appli-
cation: I have tested my boat’s charging system
and gotten some lower than normal readings,
which could be caused by a loose connection
anywhere in the alternator/battery circuit. I
start checking for a bad connection at the
positive battery terminal on the back of an
alternator. I run the test with the 225 hp
Yamaha outboard engine running, and the
alternator is working pretty hard charging up
temperature monitoring 63laser beamHere the heat gun is testing the quality of the main battery connection at
the starter motor on my engine. The thermometer shows a reading of
90°F (32°C), which is close to the outside temperature. If the tempera-
ture at the connection rises significantly when cranking the engine, a
faulty connection is indicated. In this case, all was well and no change in
temperature was indicated while cranking.some house bank batteries that have been dis-
charged.
I point my heat gun at the front of the alter-
nator and get a average reading of 186°F
(85.6°C). As I move my laser beam around a
bit, I point it directly at the stator winding
through a ventilation opening near the middle
of the alternator case. I get a reading of 211°F
(99.4°C)! As I move the laser beam to the back
of the alternator and point it directly at the pos-
itive battery terminal, I get a reading of 196°F
(91°C). As I track my laser beam down the con-
ductor, away from the alternator, the tempera-
ture gradually drops to 163°F (72.8°C).
What have I learned? Nothing, other than
the fact that the alternator gets pretty darn
hot! The wire is conducting some of the heat
generated by the alternator at the terminal,
eventually reaching the average temperature in
the small engine area of the boat.