capacitor value for latching relay?

Thanks for taking the time to make the diagram I was actually going to try it out later today.... That being said, I'll most likely end up going with 3 relays and no diodes since I have a ton of them with pigtails that snap together for a clean install....

I forgot to say that the top switch (feedback, or the actual latch "hold" signal) can also be a low voltage cutout - eg, an MW728 battery protector. Hence if you forget to turn the load off, the battery won't drain too far. I usually draw both switches because (IMO) it's easier to imagine omitting them as opposed to inserting. Hence the "either is optional" (Others can draw both or all 3 versions if needed.) Besides, that diagram is the original "sump pump" circuit - ie, pump on to empty when above the upper level. Merely invert the switch assembly to fill a tank when it's below a certain level. It's often used for alarms, or PCs with the trigger switch ommited (ie, shorted out) so the PC comes on with IGN or ACC, but stays on when the IGN/ACC is turned off until OFF is pressed (or an MW728 etc breaks the feedback). A timer can be added in parallel to the ON switch for a delayed turn on.