I am trying to add another LED to the factory alarm,but when I tap into the dash led,only one will work,not both.Any ideas?

 

I don't have any wiring schematics in front of me... but LEDs run off of a much lower voltage than the rest of the equipment in a car... which means there is a resistor/regulator somewhere... to take it down to 3.3v, or 5v... now if you were to put TWO leds on the same circuit, you may have to change out that resistor/regulator...

probably your best bet is to tie into the dash led, but use a small relay/transistor, along with a totally separate power source... that way you aren't drawing much from that original setup, which would then require different resistors and whatnot...

also, which LED does work when you 'hook' them both up? -- give us some more details...