I think I solved the starting problem on my '73B. It took a while for
the problem to reappear, but when it did I was ready with my new
multimeter.
The symptom was that the starter would turn the engine for a second or
two, but not long enough to start the car. Then the engine would turn
no more and the lights would dim. It was an intermittent problem --
the car would be fine for weeks, then it wouldn't start and I'd need a
jump. I'd take it home and leave it on a battery charger, then it
would be okay for a while.
When the car wouldn't start, I attached the voltmeter directly to the
battery terminals. Without the starter engaged, it came up to over 12
volts. When I turned the key, the voltage dropped to under 4 volts --
right at the battery terminals. The internal resistance in the
battery had grown so large that it could no longer provide the current
necessary to turn the starter.
Fortunately I had a spare battery around (remember my sister totalled
her car -- I had replaced her battery the night before her accident.
I went to the tow lot and put an old battery in her car and took the
new one). As luck would have it, the battery fit the battery box.
With the new battery, the car started right up.
I then started to wonder why the other battery died. Could it be the
charging system? I turned off the ignition and measured the voltage
at the battery: 13.1V. I then started the car and measured the
voltage at the battery 13.7V. It would seem that the charging system
was working. (Is this a valid test?)
My guess then: the older (dead) battery wasn't strong enough. The
starter current requirements on the B are large (I don't recall the
number), and it could be that as the battery aged, and as colder
weather came, it could no longer supply the needed current. I don't
trust the salesgeeks in Sears when they told me the battery was big
enough. Is this a plausible explanation (any electro-chem types out
there?)
The new battery is a much bigger and more expensive battery, with a
larger current rating. It's been several weeks since I installed it,
and there hasn't been the hint of a problem. If the problem arises
again, I'll change my assessment. In the mean time, I'll keep a set
of jumper cables in the boot.
Many thanks to Kevin Riggs, Gary Falcon, Jon Mason Gougar, Alan
Costich, Kirby Palm, Mark Banaszak Holl, Randy Wilson and Joe Flake
for their helpful suggestions.
-Josh Kablotsky
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