Jeff and Lee,

Thanks for your responses.

> 50/50 forward/reverse duty

That seems reasonable.  So there really is no issue with rewiring.

> beware of reduced holding current

I checked it out and once the solenoid bottoms out, the reduced current
keeps it very solid.  If the van hits a bump hard enough to dislodge
it, I'll have a few broken bones as well.

> both coils energized.  I've never seen it done and it might
> be hairy

In this case it is quite straight forward.  Just replace a || with an
X.  Spacers will avoid the obvious short.

> There is only a spring holding it closed, and it has to 
> be weaker than the coil's force

Not so on this contactor.  The actuator is a solenoid.  However, the
contacts are isolated from the actuator by springs.  So, at either end
of the actuator's throw, the isolation springs are compressed the same
amount ensuring that the contact pressure is the same in either
position.  So, at least in the case of this contactor there should be
no difference in current carrying capacity.

> can get ruinously high currents if it shorts the armature 
> while the vehicle is moving

I didn't think of that.  I guess that's because of the residual
magnetism in the field.  That armature sees an alternating current so
has less residual magnetism and thus generates a much smaller AC current
in a shorted field on coasting.  The paired contactors could have a
shorting overlap while switching.  My old home made switch could not.
Perhaps I should re-consider rebuilding my old switch.

Thanks for your advice,
Mike
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