What size power wire??

What size power wire should you run from the battery to the alarm and what size fuse should you use? thanks

Most alarms use a 30 amp fuse with a 10 gauge wire. This should be more than enough and just as an added installation tip, use a black insulated 10 gauge wire for the (+) of the alarm if you are going straight to the battery. This way it isn't as obvious to someone that this is a power wire when they look under the hood.Jeff

Velocity Custom Home Theater

Mobile Audio/Video Specialist

Morden, Manitoba CANADA

So i use 10gauge from battery to alarm and connect it to the alarm power which is what about 18gauge. DO i just soder the 10gauge and 18gauge together?

if you really want to get direct power to the battery instead of picking it up inside....if all it is an alarm, you could pick it up off the ignition harness.  if you really want to run dedicated wire, you can use something smaller, like 14-16 gauge speaker wire, but like he said its going to be pretty obvious..... and either way you are screwed if they open the hood, however if you are showing nothing but a stock battery terminal, it might take them that extra second to figure it out....

I thought it was better to run a line right to the battery?? So your saying it better to hook it up somewhere inside the car to get power?

The problem with going to the battery is that someone can shut your alarm off in less than about 4 seconds if they see that wire. Smash window, pop hood, and cut. Get power at the ignition harness, loom all wires in tape (or if you want to do real well - get fabric tape) and make it all "flow" with the car's original wiring. This way, someone sticking their head up under the dash has a harder job finding what wires are yours and what wires belong to the car. 90% of security is the install, the actual alarm is only 10% of the equation.

so which wire do i use in the ignition harness??

whatever the 12v constant in your harness is, or if you know of another place you can get at it?  what kinda of car is it, lets start there, and it is only an alarm right....cause if its a keyless or a remote start then you might want to be selective where you grab 12v from.....I would only use 10awg wire to the battery to a remote start sattelite.......

so if its just a basic alarm use the wire in the ignition harness, if its more like remote start or keyless entry run it to the battery with 10gauge wire?

I would just grab 12 volts at the ignition switch and not worry anymore about it. An alarm barely draws anything, maybe 10 amps when it's flashing the parking lights, and the power lead or leads at the ign. switch are well capable of more than 10 amps, more like 100 or so. Even on a remote start, as long as the main power lead at the switch is 10, 12, or even 14 guage - you would be ok to grab power for the remote start's relays there. You gotta figure that if an automaker expects that power wire to feed the ignition, accessory, and starter wires when the car is normally started with the key - the remote start does not add a bit more current draw on that same power line. All a remote start does is simply provide a series of relays that "replace" the contacts inside an ignition switch for a brief duration. I have done 100+ remote starts and grab power at the switch every time, with not a single problem so far. Alot of cars have two 12 guage power wires feeding their switches...all the better since a lot of remote starts have two power inputs. Tie one input to each wire in the ignition harness and you're on. On a car where there is only one 12 volt lead at the ignition, and the remote start has two heavy power leads; just merge the two remote start leads into one run of say, 10 gauge that goes to the ign. switch, and then tie that into the car wiring. My only other habit, that I would suggest, is soldering every single one of those connections very well, and covering with heat shrink tubing. If one of those was to come loose like I have seen alot of butt connections do, you are dealing with a high-current spot in the car that could easily do some major damage if it shorts out.