I've got a standard bosch type spdt relay with a built in diode quencher.
I'm using it to run my icm power supply right to the batt.

I tapped into the head unit hot on run wire. smaller gauge easier to work with. (which comes off the orange acc wire)

I thought I could just run the 12+ line to the cathode side of the coil then continue the coil output to the headunit...
But it wont thow the pole (trip the relay)
The relay does work if i ground it.

I'm like brand new to relays and thought tapping into another circuit the way I did would work...
Do I need a higher amp drawn line to run thru the coil?
I thought it just needed to be charged with +12v... didn't know if there was a amp requirement..
Or is grounding it the only way i can get it to work?

Pins 85 and 86 need to see a postive and negative to trip the relay, which in turn allows current to flow thru pin 30 and 87. I'm not sure exactly what your trying to do, but from what I gather you want to ground pin 85, hook up your hot wire from the head unit to pin 86. When the head until is on the relay will trip. Now hook up postive power supply to pin 30 and hook up your power wire to ICM to pin 87.

Hope that makes sense...

Yeah that makes sense.
And I did that, and it works fine.
But isnt grounding that line dangerous?
it's coming off the orange acc line. So wouldnt all the current just ground out? shorting everything else out on that circuit?

No grounding it isn't dangerous, the only way to get the relay to trip is to have a postive and ground to energize the coil (pins 85 and 86) All your doing is using your orange wire to trip the relay, use a seperate power source to power the ICM (pin 30 power and pin 87 to ICM) the coil (pins 85, 86) and contacts (pins 30, 87, 87a) and electrically isolated from one another.

Check this out...

http://www.classictruckshop.com/clubs/earlyburbs/projects/bosch/relay.htm

Ohhhh...
Ok sweet.
I thought current would be flowing thru that coil and just grounding out. I figured that would short out the circuit or something.

You have to energize the coil for it to become magnetic. if there is not any difference in voltage the current will not flow . so you need to ground it.