How do I not use control engines (monopropellant powered) in a detachable craft?

[Galactus]

Scenario:

2 stage rocket with a "moon lander" type craft at the top.

So I have control engines installed both on the rocket sections and on the lander, and I want to be able to use the ones hooked up to the rocket independently of those attached to the lander.

How do I go about doing this?

The craft is equipped with 2 command modules (an unmanned one attached to the top of the upper rocket stage, and one mk1 capsule hooked up to the lander); by default, on launch, control is granted from the mk1 (if I understand the GUI correctly... lol)

Thanks for your help!

/e Thanks Johnno!

Edited August 16, 2013 by Galactus

[Johnno]

Rightclick the tank you want to turn off and click the little green arrow thingie next to the fuelgauge. When you want to use it again remember to retoggle it.

Ugh read too fast. Right click the RCS cluster - toggle that off. You can probly set it up to action groups too.

Edit 2: when in doubt, right click.

[SRV Ron]

You can set up an action group to deactivate and reactivate them. Do note that you will have to disable the RCS tank in the lander or it's fuel may be used up by the launch vehicle first. Do so by right clicking on the fuel tank and click the green triangle to get a no symbol. With the lander tank disabled, the lander thrusters can still use fuel from the launch vehicle tank until it is detached.