list:

i should add that the voltage drop across the "gap" refered to below was
with a big load, attempting to crank. of course, a hypothetical 200 amp
cranking current across a 0.03 ohm contact resistance would have resulted
in a 6 volt potential drop, but that V-8 could never have cranked with
less than 6 volts remaining across the starter, and so it didn't. anyway,
i bring this up because even with a contact resistance, or insufficint
wire gauge, there is no voltage drop unless current is flowing. it doesn't
matter, there could be a 100 ohm contact resistance and tiny 22 gauge wire
leading from the battery to solenoid and B+ terminals on starter, and full
battery voltage relative to ground will be measured all along the circuit -
even with an inexpensive (i.e., low input impedence) voltmeter - until
someone turns the key and attempts to start - at which point the voltage
at the starter/solenoid would essentially drop to zero.

dan

On Tue, 9 Nov 2004 04:21:41 -0500, Daniel L. Katz <katzd54@YAHOO.COM>
wrote:

>oliver:
>
>chances are starter is bad. a good test is to check voltage across the
>battery terminals themselves before cranking, and then while cranking.
>voltage should drop somehat, maybe from 12.3 V down to 11.3 V or so when
>cranking. now try this with engine hot, when there is no cranking; if no
>voltage drop, then no continuity to motor windings -  probably
internally -
>but perhaps due to a bad solenoid. solenoid should at least make clicking
>sounds.
>
>if there is a big voltage drop when cranking (or attempting top crank),
>say from 12.3 V down to 9 or 10 V, then battery is probably bad due to too
>large an internal resistance.
>
>if a jump helps, then bad or marginal battery more likely the culprit.
>
>i am assuming all obvious connections/battery terminals clean and tight,
>of course. one time i was talking to a neighbor who was having a devil of
>a time with his wife's cadillac not cranking. i was kind of supporting
>myself on the positive  terminal of the battery when he tried cranking,
>and it got warm. sure enough, the terminal had just a little contact
>resistance, i guess due to corrosion, maybe .03 ohm or so is all it takes,
>and that was the culprit - an easy fix. we actually measured a few volt
>drop across the "gap" formed by the positive top post battery terminal and
>the connector on the heavy battery cable.
>
>
>dan
>