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 >