My brain isn't running at full capacity today, but I think I understand that...and it's brilliant! So simple and elegant. Why doesn't that show up in any of the web pages about automotive relays I've read? I could really use that!

Maybe not. Need to know the relay specifics to run the math.

Thanks dkjones... I know that single pole are hard to come by, but for purposes of illustration I put SPST switches & relays. I'm sure I could use DPDT relays and just ignore the extra terminals.

-Jay

sorry, after I went through all the trouble to do that, I realized that you had it strapped to latch itself.

I was too lazy to erase it all plus if someone had seen it and comented on it, their post wouldn't have made sense.

That's good of you. On my "optimal car shape" thread somebody deleted their posts and it makes me look like a wacko talking to himself.

I save that for offline. :p

No, but you did delete one of your posts in this thread.... ;)

Mea culpa. I am obsessed with revising mine to make 'em clearer. I try not to if it'll ruin somebody else's. Soemtimes I think of ways the tone could be misinterpreted too.

Just like the credits in a game show... Portions of this show not effecting the outcome may have been edited for time and content...

On my blog I've started saving drafts of posts and delaying them by a few hours, since I have a couple readers who get automatic email updates when I first publish. They were always getting the rough drafts before.

You could replace the brake light relay with a diode.
Assuming your brake light circuit is a positive switched design (one side of each bulb grounded, with switched power on the other), the wire between the switch and bulbs always sees 12V+ or ground. It gets 12V+ when the switch is activated thanks to the resistance of the bulb filaments. It sees ground when the switch is off because the unlit bulb filaments have a relatively low resistance, so small-ish currents (such as those that flow through a relay coil) fed to the bulb-switch wire can drain to ground through the bulbs without lighting them. In your design, these are the same conditions seen on the wire connecting the two relays.
The only consequence of connecting that wire directly to the brake light circuit is that stepping on the brakes would cause power to flow back through your relay coil (the ground path being the lockup solenoid), energizing it and either latching it or maybe causing it to cycle on/off (it would sound like a buzzer) as the relay contacts make and break.
To avoid that, you need a diode (a 1N4001 should do nicely and be easy to find) on the wire between your relay and the brake circuit, banded side towards the brake circuit. That will allow current to flow only from the relay to the brake circuit (when the circuit wire is grounded / lights are off), or not at all (when the circuit wire has 12V+ / lights are on).