"It's obvious that I can't sell the Model Garage any more insurance today,
Gus, so I'll take my tank of gas and go," said Harry Douglas, as he hoisted
his lanky six-foot frame from the wooden bench opposite Gus Wilson's desk.
"In case you change your mind..."
"I know where to
reach you!" interrupted Gus, grinning. "In the past month you've sent
me two letters and three postcards, all printed with your address and phone
number."
Douglas grinned in
return. "Guess that's what happens when the son of a good friend
becomes the town's newest insurance agent."
Outside, a 1964
Volvo sedan stood idling next to the line of gas pumps. Stan Hicks,
Gus's assistant, was busily polishing its windshield.
"Check the oil?"
asked Stan.
"Not unless you
can do it with the engine running," answered Douglas. "I doubt if it
will start again if you switch it off. My wife left the headlights on
last night. I had to use jumper cables and the battery in a neighbor's
car to start up this morning."
Gus chuckled.
"No problem. We'll give the battery a quick boost."
Douglas glanced at
his watch. "No time now," he said. "Anyway, my last appointment
this morning is several miles out on the main road. I'm meeting a
claim adjuster to look over the scene of a three-car crack-up, and the drive
there should help recharge the battery. I'll leave the engine idling
while I make my next few calls."
He slid into the
driver's seat, and an instant later popped his head out of the side window.
"Hey, Stan, I asked you to fill it up."
"The tank is
full," said Stan.
"You can't tell by
the gas gauge," said Douglas. "The needle reads 'empty.'
Guess it's broken, too."
"Probably nothing
serious," said Gus.
"A blown fuse, or maybe a
short in the wiring from the tank sender unit."
Douglas looked
glum. "This seems to be my day for car troubles. The radio
wouldn't work this morning, along with the electronic tachometer and the
clock. And now this fuel gauge. Gus, as soon as things stop
breaking down, I'll bring the car in so you can fix the lot."
Douglas tromped on
the accelerator, and wheeled the Volvo into the street before Gus could say
anything, but Stan recognized the thoughtful expression on Gus's face.
"It bothers me
too, boss," he said.
"Those accessories work
off different fused circuits, so the trouble couldn't be single short or a
blown fuse."
Gus spun around
and dashed into the
office, with Stan close behind. "Stan, we've got to find Harry before
he gets to that last appointment this morning. I could kick myself for
not thinking about everything sooner."
"I...I don't
understand," Stan said.
"Unless we can
stop him," said Gus, reaching for the phone, "there's a 50-50 chance that
Harry will burn out the Volvo's generator and part of the wiring harness the
instant he switches off the engine." But his call was fruitless.
What was left of
the morning passed very slowly. Harry Douglas worked out of a one-man
office, without a secretary, and his telephone answering service didn't have
a list of his appointments for the day. Neither did his wife.
Now Gus and Stan waited for the phone call they hoped wouldn't come: from
Harry asking them to tow his car to the Model Garage.
It was a welcome
distraction when a 1968 Dodge Charger pulled up in front of the office, with
a familiar face behind the windshield.
"That's the
fanciest police cruiser I ever saw," called Gus. "No wonder our taxes
are up this year."
State Trooper
Jerry Corcoran, dressed in off-duty civvies, climbed out of the front seat
and winked slyly, "just between you and me, this car can outrun most of the
cars in our fleet. It's a good thing I'm a law-abiding citizen on my
days off."
Stan cocked his
ear next to the hood.
"The idle sounds a bit
rough today."
"That's exactly
why I'm here. "The engine runs rough at all speeds, and it misfires a
lot. I think the tune-up you did last week wore off."
"Impossible!" Stan
sputtered.
"Improbable,
Stan," said Gus, "but not impossible. Let's have a look."
A small metal box
bolted to the left fender pan caught Gus's eye as he raised the hood.
"I see you've installed a capacitor-discharge ignition system," he said.
"Did the misfiring begin right after you installed the system?"
"Yes," Jerry
admitted. "But it's only a coincidence..."
Without answering,
Gus carefully loosened the distributor-locking clamp, and slowly rotated the
distributor body to retard ignition timing slightly. Immediately, the
rough idle smoothed out.
"Same old
problem?" asked Stan, a triumphant smile on his face.
"Seems like it,"
answered Gus, and turned to Jerry," "It's what Stan and I call a
'short spark.'"
"I've heard of a
short circuit," said Jerry, Looking baffled, 'but never..."
"Jerry!" Gus
interrupted. "Talking of short circuits, you're the one man who can
help me." Gus grabbed the startled trooper by the arm, and pulled him toward
the tow truck.
"Jerry, this is
important," he said. "Do you know the location of a recent three-car
accident? On the highway?"
"Sure," Jerry
said, "it's about eight miles north of town."
"Come on...you
guide me out there," Gus said. "Stan will have your car fixed by the
time we get back."
Jerry Corcoran
bounced up and down in the passenger seat, occasionally giving Gus a
direction. Finally, he said, "Since I'm along for the ride, would you
please explain what a short spark is? I'm getting more curious by the
minute."
"Well," Gus said,
"as you know, a C-D system delivers high-voltage pulses to the ignition
coil, which transforms them into 25,000-volt-plus pulses that fire the spark
plugs. These pulses are uniform, no matter what the engine r.p.m.:
That's why a C-D system improves starting and high-speed performance."
"So why the
misfiring?" asked Jerry.
"Because the C-D system
you installed, like many on the market produces a very-short-duration spark
- it lasts a shorter period of time than the spark from a conventional
ignition.
"Some
high-performance engines - like your big V-8--balk at the short spark.
It doesn't always ignite the mixture properly. When I retarded the
timing a bit, back at the garage, it allowed the air/gas mixture to
stabilize longer inside the cylinder, before the spark ignited it, insuring
proper ignition."
"Do I have to take
the system out?" asked Jerry. "Or is there another cure?"
"There is,"
replied Gus. "A very simple one. Stan will increase the gap of
all eight spark plugs to about 0.045 inches. This lengthens spark
duration, but..."
"There's a
catch?" interrupted Jerry.
"Sort of," said
Gus. "Increasing the gap also raises the voltage of the coil's output
pulses above 25,000 volts. This ignition wiring can take, so Stan may
also have to replace it with special extra-high-voltage cable."
"Fair enough,"
said Jerry. Then" "Hey, Gus the accident spot is just ahead on the
right."
Gus scanned the
scene. Three cars were jumbled at the side of the road, but no Volvo
was in sight. As he pulled up, he glanced at the rear-view mirror -
and jammed on his brakes. Harry Douglas' car was rolling to a stop
just behind the tow truck.
Gus flung
open his door and jumped out of the cab, bellowing at a bewildered Harry
Douglas: "Don't turn it off! Don't turn it off! Keep it
running!"
"Gus...what are
you doing here?" Harry Douglas stammered.
"Trying to
save you some money," Gus said as he reached into the car to pull the
hood-release lever. "Whatever you do, don't touch the ignition key.
I need some test gear from my truck. I'll be right back."
A quick
voltmeter check
proved that Gus's hunch was right: The battery was reverse-charged.
Deftly he disconnected the terminal clamps, and breathed a sigh of relief.
"I'm sure glad
you aren't on time for morning appointments," he said.
"I was
here 15 minutes ago," said Douglas, "but while our adjuster was taking
pictures of the scene, I went for a sandwich." He pointed to a
heavy-set man down the road busily working with a camera.
"Now tell me how
disconnecting the battery cables will save me money."
"This morning,"
Gus explained, "you hooked up the jumper cables backward - plus to minus and
minus to plus. A mistake like that might have caused a partially
discharged battery to explode - I've seen it happen - but your battery was
totally dead, so nothing happened."
"But the car
started okay," said Harry.
"Right," said Gus.
"The starter motor is series-wound, so it will turn in the proper direction
regardless of battery polarity. And the ignition system will work
also.
"The generator is
the trouble marker, though. The first surge of backward current
through its field coils repolarized it, reversing its output voltage
polarity. All morning you've been driving a positive-ground car.
That's why your accessories designed for negative-ground operation, didn't
work.
"Worse yet, the
generator has been reverse-charging your battery. The battery has been
reformed - in other words, its internal polarity has been switched.
Its positive plates are now negative and its negative plates positive."
"Doesn't sound
good for the battery," said Harry. "Is it ruined?"
"'Fraid so,"
admitted Gus. "But that may not be the worst of it. Kill the
ignition and we'll find out."
A continuity
proved the point: The voltage regulator's cut-out relay contacts were
frozen together.
"The sudden surge
of repolarizing current through the generator welded the contacts," Gus
explained. "They're supposed to open when the generator stops
producing an output voltage. If they don't, the generator's armature
windings become a direct short circuit to ground for the battery. If
you had turned off the engine before I disconnected the battery cables
there'd have been an enormous current flow - for just long enough to burn
out the windings and the cables linking the battery and generator."
"Ouch!" said
Harry. "I guess I owe you a vote of thanks, and a favor in return for
this mission of mercy."
"Right," said Gus.
"And you can pay your debt easily."
"How's that?"
"By passing the
word around among your colleagues that I have all the insurance I'll need
until 1999."
END
