Torque converter lock-up circuit

I have a GM TH 350 auto transmission with a locking torque converter.  Somebody wired a nice latching relay to the momentary switch on the gear lever to turn in on and off.  Trouble is, one has to remember to switch it off when you stop or the car stalls.  Easy to fix with a SPDT relay from the brake switch but, of course, if you take your foot off the brake, the thing locks up and the car stalls...  I need a circuit whereby when the brake is applied, power is off UNTIL it is manually switched on again - can anyone suggest a circuit or a type or relay that will do this?

Thanks, Peter McEwan

You can get a latching relay and trigger it off of the brake switch.  You would then have to put some type of switch to flip the relay back to normal position.  I don't know if this helps, I'm not to familiar with your application so sorry I can't be more specific.

I thought of this but then the brake would turn the locking mechanism on and off.  So, if I were to apply the brake to stop the vehicle then, for some reason, release the brake and apply it again, the torque converter would lock up again, even if the vehicle is at a stop.  Ideally, I need one relay that would only initiate the lock, such as from a push button, and one that would only switch it off but not be able to re-iniate the circuit - sort of like a cruise control.  The crux of the thing is to find a way wherby the brake switch can break the circuit to the torque converter and it stays off when the signal from the brake switch goes off again and the locking sequence has to be reinitiated separately.

thanks

Might have a solution for ya.  You'll need 3 relays and a push button momentary switch.  I'm going to run under the impression that the torque convertor takes a positive signal to lockup.  I have to put it together and test it, I'll post it up if it work when I get home tonite.

Here's a diagram that should work.  The relay on the right supplies the power to lock up the converter.  When the momentary switch is pressed, it activates the relay on the right, which sends power to the torque converter and to the relay on the left, which latches the relay on the right, until the brake is applied.

The drawback to this two relay setup is, the only way to unlock the converter is by applying the brake.  Once the brake has been applied, you have to press the momentary switch again to re-activate the relay latch to lock the torque converter up again.  If you want to be able to press the momentary switch to deactivate the latch, it would require adding more relays for this feature.

Thanks, guys - I'll try it.

P