accessory wire

i am using a relay to turn on an inverter when i turn the key, left or right....my question is  if i hook the acc wire up to the relay, will it only have power when the key is in the acc posistion? i need it to have power in the acc posistion, on posisition and starting posistion, so that it doesnt shut off after i leave the acc posistion, or while starting. 

would it be okay to tap into the accessory wire in a car stereo harness to connect to the relay? id rather not tap into the accessory in the igntion harness, and will i be needing diodes for this setup?

thanks

Yes the proper ACC wire will work but use the one running to the igniton harnness as this will provide more current rater than overloading the radio acc wire. Depending on what you are hooking up, the current draw may be to high causing the wire to get extremly hot or better yet melt causing serious conditions including possible fire.

Jeremy

Okay I will just tap into the acc wire in the igntion harness then,  its just going to be used to turn a relay on, so its not going to be powering anything big,  but the relay will be powering a 350watt inverter.  should i use a diode just in case on the acc wire from the igntion harness just to be safe?

what size fuse will be enough? i have a few fuses that were in a cigarette lighter power adapter lying around, will that do the job? or do i need something higher?

will the lose in voltage be long enough to open the relay so my inverter will shut down while starting?