You have two circuits in the solenoid, a "start" circuit and a "hold" circuit.
It takes more electromagnetic force to start the solenoid moving than to hold
it in place. The higher force is generated when you first turn the key to
start moving the plunger. Both wires are generating electromagnetic force.
Once the contacts are made, you'll have 12V on both sides of the larger wire
and no current will flow through that circuit. Only the smaller "hold" circuit
will be energized until you release the key. This system allows higher
reliability in solenoid engagement without generating higher heat and risking
burning out the solenoid sooner. Hope this all makes sense.
Steve (in N.Id.)
----- Original Message -----
From: Jerry<mailto:JCMC2006@suddenlink.net>
To: TIGERS@AUTOX.TEAM.NET<mailto:TIGERS@AUTOX.TEAM.NET>
Sent: Thursday, October 30, 2008 11:23 AM
Subject: [Tigers] Starter solenoid
List,
Here is a question for all those electrical/electronics engineer types out
there.
Being the curious person I am I decided to cut apart a Ford starter
solenoid
that was acting up, it was giving a little "chatter" as it engaged.
Now these things are sealed at the factory and not intended to take apart
for any service, but I'm always curious.
The specific starter I'm talking about is the small geared starter that is
on most all the ford engines since the early 90's, and fits very well on
our
Tigers. They are lighter, more powerful and draw less power. And if you
have
headers you can take them in and out without removing any thing else. Two
ways to wire them up, either works just fine. Mine has been in for 8 years,
I bought it at a junk yard for $30.00.
The symptom that my friend had (347 Ford race car) is as I said in the
beginning it sounded like a little chatter when engaging, as if the
solenoid
was "bouncing" before finally engaging. I removed the starter and tested it
and it would run just fine except for the chatter so I concluded that the
solenoid may be the problem, a new one solved the problem.
Now to the question. I cut the solenoid apart, there are two windings in
the
solenoid, one with a dia. of .23 the other is .41. The larger wire is
connected so when 12V is applied to the small tab on the outside of the
solenoid (normal attachment point) the plunger inside reacts and closes the
large contacts to send the high amperage to the motor, all simple stuff.
It's the smaller wire I'm wondering about. It is attached in the same place
as the larger wire (where the 12V start signal is applied to) on the out
side, but it's where these two wires are grounded that I'm wondering. The
bigger wire (.41) is grounded to the large external (13mm) nut that goes to
the starter motor, the smaller wire (.23) is grounded to a metal plate
inside the solenoid (by the way that was the problem, that attachment had
broken). The question is; why two different windings and why the two
different grounding points? (The smaller wire is a little longer).
Jerry Christopherson
PS Anyone else going to SEMA?
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