"Some people always want things in a
hurry," grumbled Gus Wilson as he hung up the receiver and shoved the
telephone away from him. Joe Clark, perched on one corner of the desk,
grinned sympathetically.
"What's the trouble now?" he inquired.
"Somebody run out of gas?"
Gus shook his head. "It's Ted
Cummings again. Something's wrong with his generator and as usual he
has to have the car tonight."
Fifteen minutes later, the grizzled
garage man had his gray head buried deep under the open hood of Cummings'
car.
"Now let's get this straight," he
said, fingering the black wires that snaked their way to the distributor.
"When you started out this morning everything seemed to be O. K. and the
ammeter was charging fifteen or eighteen amps. Then the pointer
snapped over to the discharge side and it stayed there until you shut off
the ignition."
Cummings nodded. "And it
happened again coming over here," he said.
Gus placed his hand on the metal
cylinder that housed the generator. "Suppose we try her again and see
what happens," he suggested as he walked around to the driver's seat and
turned the ignition switch. A glance at the ammeter showed the normal
few amperes' discharge.
"So far, so good," commented Gus.
"Now to step on the starter."
"Gosh," exclaimed Cummings as Gus
opened the throttle and raced the motor. "She doesn't even show charge when
you start now. That needle hasn't budged."
With a satisfied grin, Gus shut off
the ignition and went back to the side of the motor. A few minutes
later he loosened the clip that held a small cover plate to the side of the
generator housing. As the plate dropped free and exposed the brushes
and commutator, he tapped a small rectangular plate that was also visible.
"See that?" he asked, pointing with
the tip of his screw driver. "That's your generator thermostat and
unless I've got my signals crossed, that resistance you see mounted on top
of it is burned out."
"A thermostat?" questioned Cummings.
"I've heard of a thermostat in the
radiator, but a generator thermostat is a new one on me."
"Not every car has one," explained
Gus. "But this one does. It's like the gadgets they use to
regulate a furnace or an electric iron. You know, a bar of metal that
bends under heat and breaks an electric circuit.
"Well, the generator thermostat opens
and closes according to the heat of the generator and the surrounding air.
When the motor and generator are cold, the electric contact points of the
thermostat are closed and full current from the generator goes to the
battery.
When the generator warms up, the two
contacts spring apart, and instead of flowing to the battery, the current is
side-tracked through this resistance and then to the battery.
Naturally, the extra resistance cuts down the generator output and reduces
the charging rate."
"But what makes you so sure the
resistance is burned out?" inquired Cummings.
"From the way your ammeter acts, it's
a cinch something is breaking the circuit when your motor warms up. A
burned-out resistance would fill the bill pretty nicely wouldn't it?"
"Then, how do you account for the way
the ammeter acted a minute ago when you started the motor," asked Cummings.
"It didn't even register charge in the
beginning."
"That's easy," replied Gus.
"Your generator was still warm from your ride over here. Naturally,
the thermostat points were still open and the circuit from the generator to
the battery was still broken. As a matter of fact, it was that little
test that made me sure it was the resistance."
"Can you put in a new one?" inquired
Cummings.
"Sure, but first we'll have to find
out what made the resistance blow. Besides controlling the charging
rate, that resistance is a generator fuse and when it burns out it's a
pretty good sign there's a burn connection somewhere that's been overloading
the generator."
Once again, Gus buried his head under
the hood and proceeded to tug at the various wires that ran from the
generator and the stating motor to the battery.
"One thing certain," he announced at
last. "We're going to find that bad connection somewhere in the
charging circuit."
Gus soon found that a generator
terminal had caused the trouble and a few minutes later he finished
replacing the burned-out resistance and announced that the car was as good
as new.
"That sure had me guessing," said
Cummings. "Sort of mysterious wasn't it, the way that ammeter would
jump to discharge?"
"A car's ignition system is chuck full
of mysterious troubles," replied Gus. "A fellow came in just the other
day. Claimed his car had no pep, was hard to start, and heated up.
After spending about two hours going over the ignition, spark plugs, and
carburetor, I traced the trouble to the distributor. The spring that
operated the breaker arm and points had got weak and wasn't forcing the
contacts closed the way it should."
"How did you find that out?" asked
Cummings.
Gus walked to his repair bench and
picked up a small spring balance. "I borrowed this tool from my
fishing kit," he said, holding the scale up so Cummings could see it, "and
it comes in mighty handy testing distributor springs and touch springs.
Here," he added turning back to Cummings; car, 'I'll show you what I mean."
When he had loosened the fiber
distributor cap, Gus indicated a U-shaped spring on the breaker arm and
proceeded to slip a loop of wire attached to the lower end of the spring
balance over the tip, "Now this spring has good tension," he explained as he
pulled the other end of the balance. "If you'll look closely, you'll
see that the balance reads just about eighteen ounces. That's just
about what it should be.
"The same thing holds true for the
springs on starting motor and generator brushes," he continued as he
reassembled the distributor, "just hook the balance to the brush arms and
pull. The balance ought to show a tension of about twenty ounces."
"Never knew you could use a spring
balance round a car," said Cummings with a chuckle. "And I never
realized that you could tell so much about the electrical system just by
watching the ammeter."
"Or the needle may jiggle back and
forth instead of staying steady. That indicates a loose or corroded
connection in the lighting system or in the ignition wiring.
"If you're breezing along and your
motor suddenly goes dead, a glance of your ammeter will generally help you
to find the trouble. The thing to do is turn on your ignition.
If the ammeter pointer stays at zero, there's either a break in the primary
of your ignition coil or the breaker points have turned away or jammed open.
But if the ammeter shows the usual discharge, you can forget about the
breaker points and ignition coil primary and concentrate on the condenser,
the high-tension winding on the coil, and the high-voltage wiring to the
distributor and spark plugs."
"By the way, Gus, speaking of
condensers, is there any simple way you can test a condenser when you're
stuck miles out on some lonely road."
Gus nodded, "And your ammeter will
come in handy there, too. All you've got to do is wedge a piece of
cardboard between the breaker points inside your distributor and turn on
your ignition. If the ammeter reads discharge, it means current is
flowing even though the points are open. The only other route is
through the condenser, so it's good proof the plates are short-circuited at
some point inside."
"Say, you haven't got a bottle of
glass cleaner or window polish around the garage, have you?" asked Cummings
with a grin as he climbed into his car and prepared to drive away.
"Glass cleaner?" questioned Gus.
"Sure, I thought I'd clean up the
glass on this ammeter so I can watch that confounded pointer a little
easier," replied Cummings with a chuckle as he maneuvered his car out of the
garage driveway.
END
