Joe Merone wrote:
"Battery to positive side of the coil (engine off) -
12.45 volts"
What you are reading here is battery positive to ground, except you are
going through the coil to ground. A voltmeter has a high resistance, so there
will be no apprecialble current flow, so no voltage dropped across the coil.
You
should read very near battery voltage, regardless of what kind of coil you
have.
"Ignition key on, wire attached from negative coil
terminal to engine ground, voltage read from positive
coil terminal to different engine ground - 8.05 volts."
This is a meaningful test. What you are seeing here is the voltage drop
through a ballast resister. With the coil negative grounded and the key on, you
will be drawing maximum current through the coil, and through the ballast
resister, if any. If you had no ballast resister, you would only see a voltage
drop through a plain piece of wire, which is virtually zero. A ballast
resister,
on the other hand, has a high resistance, and will drop voltage to the coil.
Which is what you saw with your 8.5 volts - the ballast dropped the other 4
volts.
"Resistance across coil terminals with all wires off -
3.5 ohms. It's a Bosch coil (aprox. 20 years old)."
This coil has enough resistance to not need a ballast resister. you need to
bypass you ballast resister. I wrote an article on this on the VTR website
_http://www.vtr.org/maintain/ballast.html_
(http://www.vtr.org/maintain/ballast.html)
Regards,
Dan Masters
Check out the new British Cars Forum:
http://www.team.net/the-local/tiki-view_forum.php?forumId=8
|