Anyone know what an acc wire can handle?

panzermajier · 04-23-2008, 05:12 PM

Hey im planning to hook up two relays and possibly a voltmeter in addition to my amp to the blue ACC wire that is running out of my dash behind the radio. dose anyone know roughley if it would be able to handle that much stuff? and if it can't how else could i hook this stuff up to have the same effect? Also anyone who knows about how many amps a standard ACC wire is usually fusd at That would be extreamly helpfull. I've been looking all over the place for info about the acc wire but I can't find much of anything. Thanks.

panzermajier · 04-23-2008, 05:15 PM

oh also i forgot to mention that the car is a 99 chevy lumina idk if that helps at all.

Bugbyte · 04-23-2008, 10:40 PM

STOP right now before you cause a fire in your car.

The amount of power a wire can carry depends on its gauge, the length of the run and the fusing. If you do not know all three of these items and why they matter, do not hook anything up to your accessory wire, particularly the amplifier.

Most car amplifiers require a dedicated power line that is properly fused and of sufficiently heavy gauge to carry the load of the amp. The FAQs section has some good reading on determining the proper gauge wires for the load you require.

Accessory wires in cars are usually not capable of carrying a heavy load and are most commonly used in aftermarket applications to signal an amplifier to turn on or a car PC to start up and so forth. The signaling function draws very little power. The actual electrical load for these devices is properly carried on a separate line.

You need something like a car amplifier installation kit, but you also need to figure out how much power you will require so you can get the proper sized kit.

Edit: there is some talk related to this topic on a parallel thread here

panzermajier · 04-24-2008, 12:01 AM

im sorry i must have been unclear with my question. I am not hooking up the amps power supply to the acc wire I have 4 gauge runnng to my battery the normal way and into a dristributor block for the amp and inverter. when i said hook up the amp I ment the remote turn on. I also want to hook up two relays one to turn on my inverter, and one to turn on the car pc. I also read that the acc is the easiest place to hook up a voltmeter so i wanted to put that on there as well. I am not trying to power anything from the acc. my question is if the wire can handle that all of those. thanks

audiology · 04-24-2008, 02:04 AM

If it's a stock unit the fuse is usually located at the fuse box.

Bugbyte · 04-24-2008, 07:40 AM

Thank goodness! Sounds like you have it hooked up properly.

Unless those relays draw much power, you *ought* to be fine on them. One way to check is connect something to the accessory line, like the voltmeter. Turn the key on and pull fuses until the voltmeter goes out.

Then, using a multimeter at the fuse block measure the amperage being drawn on that line. Verify that against the amperage on the fuse.

JimmyFitz · 04-24-2008, 08:04 AM

Your voltmeter can be hooked up anywhere without concern about how much current it draws. Instead of using two separate relays, you can get a double pole relay and use it to control two separate circuits. There are also 3-pole and 4-pole versions.

panzermajier · 04-24-2008, 01:21 PM

Thanks guys both very usefull answers. I dont know anything about voltmeters so I was somewhat concerned about how much current it drew in relation to relays so I feel alot more confident about my circuit knowing that.

rybitski · 04-25-2008, 09:50 AM

Most automotive relays use less than 1 watt (thats right one watt) of power. So if your acc line is fused with a 5 amp or higher fuse (the lowest fuse in my car is 10 A) then you will be fine. Go relay crazy, just make sure you are only using the acc to trigger the relay and not provide power tho, as people have said earlier.

And they are right about the voltage meter, they are passive electronics which means they do not put a load on the circuit you are monitoring.

Good luck.

pancit175 · 04-27-2008, 06:59 PM

I would suggest, if you havent already considered it, use a relay to isolate your voltmeter from the acc line for the reason of getting a more accurate reading if you'd like.

Also a typical bosch style relay only requires 200mA to energize it, so long as it is in good working order.

rybitski · 04-27-2008, 09:54 PM

Quote: Originally Posted by pancit175

I would suggest, if you havent already considered it, use a relay to isolate your voltmeter from the acc line for the reason of getting a more accurate reading if you'd like.

This makes no sense and would not provide a more accurate reading because the acc voltage comes from the battery, just like any other positive wire in the car.

walky_talky20 · 04-28-2008, 10:08 PM

Although in most cases it wouldn't matter, pancit175 has a point. Depending on how much load you are putting on your ACC wire, and the guage of the wire, it could give you a somewhat lower reading that is not necessarily reflective of the battery voltage. As the draw increases on the ACC wire the voltage on that wire will be somewhat lower, even if the battery voltage has remained constant. Running a separate wire for the volt meter, and simply signaling-on the meter with the ACC wire would be more accurate. How much accuracy is required or whether this small difference is even measurable would be debatable.

Peace