2 potentiometers, one circuit

FYI - Without further circuit analysis, I figure a 3.3k between green & yellow, else a 5.6k between yellow & orange (to change the alarm from 6500RPM to ~ 3,000RPM).

Oh another question since this circuit used to be a tach, it has a shiftlight output. How would I connect that to my alarm LED? My alarm led is very visible and I do not want to add an unsightly shiftlight in my interior so I was hoping to make the LED dual purpose.

You need to get to the 2 wires of the LED, and if you can put the alarm in valet mode to make the LED illuminate steadily, do that and check the DC voltage across the 2 wires.   Then with the LED turned off, I need to know if there is any voltage on either of the wires, using the vehicles chassis as a ground reference for your meter.

The device works as intended with the 2 pots installed thanks! The voltage for the led with my ground probe on a chassis ground (key slot) is 2.8v for the red wire and 00.01v for the black one. When the LED is off it is 0v for both.

Set the meter to ohmns and check the resistance from each wire to chassis ground.  If the ground wire of the LED is common with ground under both of the previous conditions, it will be possible with a single relay and a resistor. 

I also need to know if the shift light is a 12 volt bulb?  Do you have any idea of the current capacity of the shift light output?  A standard Basch/Tyco relay will draw 160MilliAmps.

With the LED on: Red wire 1     . thats what my multimeter says Black wire 00.6 - 00.9 fluctuates when i move the probe around With LED off Red wire 00.06 Black wire 00.2 I probed the 2 pin shiftlight plug and it reads 14v when the car is on. The bulb it uses is a normal incandescent bulb. Both pins read 14v and one drops to 10v when im hitting the limiter so does that mean its ground pulled? My limiting relay is hooked up to this shiftlight output which ground out the ignitor coil on and off hence limiting the rpms if you wanted to know how it works.

Cut the red wire between the LED and the brain.  Insert this relay.

Text on the right reads: Existing LED wire, this end to alarm brain.  Install a diode across the coil of the relay.  Banded end of the diode on the positive wire.  Non banded end on the wire that goes closer to ground when the lamp illuminates.

Thanks I'll try it out. I don't need diodes to stop the 12v from going into the alarm brain or from the alarm brain to the shiftlight circuit? And when you mean existing LED wire do you mean the positive? Can I use a 1k ohm 1/2 watt resistor?

The diode is only to protect your LED and your shift light output  from the backlash of the relay coil.  It will probably be OK without one, but in case you have not yet figured out, I really do not want any of your equipment to fail on my watch.  Yes a 1/2 watt resistor will be twice as relaiable than a 1/4 watt device.

Yes I understood the function of the diode on the coil thanks for always coming up with safe diagrams. I will try this now. I hate reading color bands on resistors as I am color blind haha