Lude Generation

I'm trying to repurpose my air conditioning circuit. I don't have AC any more (no compressor or condensor) but the wiring is still there and the button lights up.
I can't find anything that powers up 12v when I switch it on though. Does anyone know where I might be able to tap into it?

The circuit is more complicated than just an on/off switch. With a full aircon setup, there is a pressure sensor in the circuit, and this in conjunction with the switch, would put 12v on the AC clutch wire (the single wire that goes to the AC compressor). The idea is that the AC pump shuts off under high pressure or no pressure in the system (to avoid damage).

If whilst removing the AC system you have removed/cut off the sensors/loom, then you are going to have a hard job trying to re-purpose it. I suspect you would need to 'short out' the pressure sensor part in order to fool the circuit into thinking 'I have AC refrigerant pressure so ill activate the relay and in turn the clutch wire'.

Thanks, I'll look into that. I think I binned the pressure sensor, but the connectors should still be there. If I can figure out the resistance I might be able to fool it.

So, I have an unexpected result. I tested the connector for the pressure sensor and here's what I found:

Engine off: nothing.

With the engine running and AC OFF: Both pins 12V+

With the engine running and AC ON: (looking at the plug as though the clip is at the top) Left pin 0V, Right pin 12V+

That seems a bit odd, but it does mean that I can use this as a switch (even if it's back-to-front), so I'm going to wire this up to a relay and give it a go.