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Understanding the battery solenoid

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TomFromStLouis

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Help me understand the solenoid that is between the battery and starter motor and coil etc.

For example, what is the button on the back of the solenoid used for? I remember back when it still had the rubber over the button I could use it to start the car somehow.

Here is the reason I am asking all of this: the car would not start and a kindly stranger simply pushed the button several times and the next turn of the key started her right up. Is that button some kind of reset? If so, why did it not work again this morning? There is something going on in that very part I do not get at all. Tell me all about the button and what it does.
 
Your dash starter button activates the starter solenoid. The button on the back of the solenoid does the same thing. It's useful when working under the bonnet to bump the motor over, such as when doing valve lash and static timing. Keep the boot-mounted safety switch on, but don't turn on the keyed ignition switch on the dash and you'll be able to do your under bonnet fiddling without walking around to the dash and without firing up the motor.

When you say it's not starting, is the starter engaging or is it failing to fire once the starter engages?
 
The starter is not engaging. I only get a loud click and then nothing. Perhaps my solenoid is going bad because pushing the button does not even give me the click.

Thank you restorethemall for the Moss link. It is precisely the kind of education I needed.

ps - I have a BJ8, so no starter button on the dash, just a turn the key thing.
 
TomFromStLouis said:
The starter is not engaging. I only get a loud click and then nothing. Perhaps my solenoid is going bad because pushing the button does not even give me the click.

Thank you restorethemall for the Moss link. It is precisely the kind of education I needed.

ps - I have a BJ8, so no starter button on the dash, just a turn the key thing.
Click to expand...

Are you sure your battery and cable connections are good. Sounds like the battery's dead and the solenoid is clicking but not turning the ring gear.

PS - don't jump the car without ascertaining whether it's positive or negative ground.
 
Having taken them apart__what, doesn't everybody?__I can tell you why it's no longer working. This of course assumes that your battery and cable connections are indeed good.

As Derek states, it's just an electrically operated contact switch, a high-current relay, so you don't have to have #4 gauge wire running up behind the dash (the smaller the # the larger the wire diameter).

inside are the contacts, and each time it is activated, there is some transfer of the copper material from one contact to the other, arcing as they are closed and opened during the high electrical current load of the starter motor. If the switch were of an open design, you could watch it throwing fire.

In the past, I have taken them apart and filed all the pits back to a flat surface again, but inevitably, the contact surface erodes even faster, and before long, it can no longer pass the current__just too much resistance on the surfaces of the contacts.

While turning your key electrically pulls the contacts together, pushing the button on the solenoid manually makes/breaks the circuit. The time the kindly stranger did it, he just made it arc enough until the current path was completed.

The bottom line is, and I think you already know this, is that you need a new solenoid__again, assuming you've already determined the battery and cable connections to be free of fault!
 
Thank you Randy. I checked and cleaned the battery terminal connections and the solenoid connections which seemed to not to be much needed except to confirm your point. I am ordering a new solenoid.
 
Make sure the battery cutoff switch is good. It can develop high resistance just like the starter solenoid and all you will get is that "click" without starting.
 
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