Relay advice please

Cobbling together a relay switched immobiliser for my 2.5 petrol 90 that cuts the supply to the ignition,and for a belt and braces approach I would like to immobilise the fuel pump too.

The immobiliser is armed via a NC switch which when opened activates a DPDT relay which in turn feeds a standard 30A 4pin relay that cuts the ign supply; to disarm a hidden NO reed switch is activated which when closed activates the DPDT which triggers the 30A relay to complete the ing/fuel circuit.



So, can I interrupt both circuits, ign & fuel, from the one 30A relay or should I use two, and if so how do I wire them together?

Thank you.

A hidden normally open switch will when closed will supply voltage to operate a relay, which will operate and cut both the ignition and fuel pump circuit. Simples
You don't have or need a relay to operate a relay.

Thanks for the reply. It's not my idea, several web sources and an amalgam of what seemed workable.

A single push of the NC pushbutton breaks the latching circuit of the DPDT relay, causing the relay to open and stops power flow to the 30A relay, in turn disabling the ign/fuel circuit. It also connects the LED to 12 volts, causing it to flash. Disconnecting the car battery switches off the flashing LED but makes no difference to the position of the DPDT relay.

Momentarily closing the reed switch allows power to flow through the DPDT relay's coil which pulls in, with the second coil power supply path through the top contact causing it to stay pulled in, even after the reed switch has opened. The bottom contact of the DPDT relay then feeds power to the heavy-duty relay, causing it to pull in and complete the car starting circuit.

Are you saying I can do all of the above with one relay? If so would you mind posting a schematic? Anything to keep it simples, but I like this because the arm/disarm are sited and activated separately.