Re:
>> Battery cable goes to contactor ("automotive: solenoid"); another cable runs from contactor output to starter solenoid. "Start" circuit energizes the contactor coil, closing high-current path to starter/solenoid. When start signal is removed, starter continues to spin.
>>
>> [||B||]-----------(C)-------------(S)-(M)
>>
>> The latter case is generally because the contactor has stuck "connected" (welded). If you want to prevent this from happening where you can't get out and disconnect it, wire two contactors _in_series_ with the start terminals in parallel, so that they are energized simultaneously.
>>
> My first solution was as above with the contactor and the solonoid activated together. This failed.
>
>
>> [||B||]---------(C)--(C)-----------(S)-(M)
>>
>> Now, if either contactor sticks, the other will still break the high-current circuit, and the motor will stop.
>>
> Don't you actually have three "contactors" above: the solonoid is also a contactor.
>
Actually, only if the "start" circuit also goes to a separate terminal on the starter/solenoid package. Often, where a separate contactor is used, the "start" terminal on the starter/solenoid is simply wired to the incoming power cable, so as to energize as soon as current is available from the contactor. It simplifies the circuit by not requiring an additional wire to from the start switch to the solenoid.
>Surely if two didn't work going to a third is not worth it. As I see it the solonoid has a short that provides power from voltage to its' contactor terminals to it's winding terminal. Since my second contactor is in parallel with the solonoid windings this short activates it as well. The probelm is resolved by not using the contactor terminals on the solonoid but just using it to through the gear in. Power from the first contactor goes to motor.
>
As I just pointed out, that "short" in the starter/solenoid may be designed in. The real question to answer is whether there is voltage on the "low" side (not battery) of the contactor when the "start" signal is removed from from the "start" terminal. If there is voltage, then the contactor is bad. Remember, a contactor is merely a high-current relay. It should have only two states: open circuit when the coil is not energized (via the "start" coil) or dead short when the coil is energized.
Hope this gets you closer to a solution.
Dale
Hello Dale.
I'll comment in your text below:
Please correct me if I am wrong, but from the description, it sounds
as though you have the following setup:
Battery cable goes to contactor
("automotive: solenoid"); another cable runs from contactor output to starter
solenoid. "Start" circuit energizes the contactor coil, closing
high-current path to starter/solenoid. When start signal is removed,
starter continues to spin.
[||B||]-----------(C)-------------(S)-(M)
The latter case
is generally because the contactor has stuck "connected" (welded). If
you want to prevent this from happening where you can't get out and disconnect
it, wire two contactors _in_series_ with the start terminals in parallel, so
that they are energized simultaneously.
My first solution was as
above with the contactor and the solonoid activated together. This
failed.
[||B||]---------(C)--(C)-----------(S)-(M)
Now, if either
contactor sticks, the other will still break the high-current circuit, and the
motor will stop.
Don't you actually have three
"contactors" above: the solonoid is also a contactor. Surely if two didn't
work going to a third is not worth it. As I see it the solonoid has a short
that provides power from voltage to its' contactor terminals to it's winding
terminal. Since my second contactor is in parallel with the solonoid windings
this short activates it as well. The probelm is resolved by not using the
contactor terminals on the solonoid but just using it to through the gear in.
Power from the first contactor goes to motor.
BTW, back when I used to install Ford engines in strange places, I always
took care to mount the contactor with the coil UP, so that gravity would work
for me in opening the circuit, should the spring
fail.
Dale
Bob:
Yes, but come to think of it, IF the Mazda solenoid is
just an electrical contactor, not also a gear engagement mechanism (I don't
know), you could bypass the original solenoid altogether.
Oh-oh, my book indicates you have to use both. The
original engages the gear.
Bob Darrah
Yes it does engage the gear so I did wire the two
solonoids in parallel on the activation wire but I disconected the battery
cable from its' normal input side of the mazda solonoid and put it on the
side that has the cable going to the motor. This way (I thought) no current
is going through the mazda solonoid contacts. In spite of my being
convinced this would solve the problem, I regret to say there is no change:
stays running after starter switch opened.
So doesn't this have to mean that power is getting from
the contacts to the coil of the solonoid???.
Peter
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