I hate Radio Shack

From: Dwight K. Elvey <dwightk.elvey_at_amd.com>
Date: Wed Jun 12 18:14:54 2002

>From: ard_at_p850ug1.demon.co.uk
>
>> The guy there is accustomed to seeing me come in for DE9 connectors,
>> hoods, & computer stuff, and always asks "What are you building this
>> time?" He doesn't know anything, but at least he's curious... I found
>> a push-button rated at 3A, 125VAC, and brought it up. Darrell says
>> "Building one from scratch now, are ya?" I told him no, it's a starter
>> switch for my pickup. He refused to sell it to me, because "Those
>> starters pull 20 or 30 amps, and that's *DC*, too! That switch will
>
>Hmm... In every UK car I have worked on, the starter motor itself draws
>about 600A on-load from the battery. This current is switched by the
>starter solenoid contacts which acts (in part -- it also moves the
>pinion into mesh with the flywheel) as a large relay.
>
>But the solenoid coil draws significant current as well. There are
>typically 2 windings, one to pull the core in, one to hold it. The
>former typically draws about 17A, the latter about 4A.
>
>Now, admittedly the former should only operate until the solenoid has
>pulled in, But if there are problems (a typical one is a relatively high
>high resistance connection in the circuit which limits the current to
>(say) 10A -- the solenoid will then not pull in and disconnect the first
>winding), then the current through the switch will be a lot higher than
>you might expect.
>
>I certainly wouldn't use a 3A AC swtich for a starter solenoid operating
>button. It's way underrated.
>
>-tony
>
>

Hi
 I have never seen this on a solenoid type of starter relay.
The switches on the solenoid were always for the ignition
resistor bypass and the main switch for the starter motor.
The only time I've seen this is on the Ford type starter where
the pull in for the gear comes from a pole piece in the started
motor. The pole piece would pull in and change the field to be
series with the motor armature. There was a separate solenoid
that powered this and it always had the full coil current and
only switched the current to the starter and the ignition
resistor bypass.
 Pinball machines do have what is called a EOS ( end of stroke )
switch that is used on flippers to reduce the current for holding.
Dwight
Received on Wed Jun 12 2002 - 18:14:54 BST