I need a circuit that switches a relay on with a momentary switch, yet is forced off by a different momentary switch ...

I'm wanting to implement a manual TCC lockup.
E.g. I hit a dash switch to enguage the TCC relay, but then the brake could then kick it off (until I again hit the dash switch to re-engage).

I think this is called a "latching relay", but the only circuits I could find wouldn't fit my needs.

I'll find out for sure tomorrow, but I'm pretty sure a relay needs a constant 12v to the coil to stay switched. I know a guy that's a relay wizzard, I'll tell him what you want to do and I'm betting he can come up with something.

no there is such a thing as a latching relay that kinda goes over center then you can remove power to it, I have an LDG tuner that has like twelve of them in it, it tunes up and then you can unplug it to save juice.

I'm not familiar with autos but from your description I reckon that you need 2 relays. The latching relay for the TCC and then an ordinary relay in line with the power to the TCC relay. Wire the normal relay's coil to the brake light and the power feed to the TCC relay through the normally closed contacts. Then when you hit the brake the power to the TCC relay will be cut and it will switch off.

Rhinoman is a genious that will work great and you can use two cheap off the shelf aftermarket light relays buy 3 for like $12 and have aspare and some offroad light wiring kits even come with a nice 4 wire plug in block!!!! wished I would have thought of that!!!

Check the following link for a description of latching relay operation.

http://zone.ni.com/devzone/cda/tut/p/id/3960

There should be some 12 to 14V relays out there that will work for you.

thx rhino ...

Would it also work to have the normal TCC relay in place, and then have a latching controlled by the push button and brake switch? (aka a flop of your description).

I wonder ... how's the "4dr rear defroster" switch work? (I suspect it might be a "latching momentary", that is "unlatched" when the ignition is turned off).

I have one of those in a box someplace I might dig out to experiment with.

That would be PERFECT since it'll also snap into a factory dash cutout !!!!

thx rhino ...

Would it also work to have the normal TCC relay in place, and then have a latching controlled by the push button and brake switch? (aka a flop of your description).

I wonder ... how's the "4dr rear defroster" switch work? (I suspect it might be a "latching momentary", that is "unlatched" when the ignition is turned off).

No idea about the normal TCC relay.
I have a soft-top so I don't know about that either. On mine the rear fog light switch latches and then turns off with the ignition. I haven't looked at the circuitry though, sounds similar.

yea, I'll examine the FSM wiring diagrams and see if I can figure something out.

Pardon my ignorance, but what does TCC stand for?

To the problem:

As I understand it, you want a device that, when one momentary closure is made on a switch, a relay closes which controls the TCC.  Then, when you step on the brake pedal, another momentary closure is made with a switch and the TCC controlling relay opens back up.

This sounds like a job for the BASIC Stamp!!

It's a cheap Programmable (some I-word... Instructions?) Computer or PIC that can be programmed with a form of the BASIC language to exactly this task.  Dare I say "trivial"  ?  You could also use it to sense and display coolant temperature, act as a tachometer and other stuff too!

I smell a product - assuming lots of folks want to control their TCC..   

This sounds like a job for the BASIC Stamp!!

No no no no no no no no no no no no no no no no no no no no no no no no no no no, please god no.