New HU Installed!

[huskyfan23]

I just got done installing an Alpine CDA-7894. All the speakers are working fine, but I have a quick question. The instructions said I needed a 20A fuse wired to the battery. I bought an inline fuse holder that had 18 guage wire coming out of both ends. I added 8 gauge to that wiring, so is that fine or should I get a better fuse holder?

 

[DeRocha]

Fire hazard


A 20a fuse with 18ga wires connected to 8ga wires will melt the 18ga wires long before the fuse blows...

The fuse is designed to protect the wiring. As such you match the fuse to the Smallest gauge wire in the series (which is 18ga in your case). Therefore you cannout use a fuse larger than 5a. You will need 12ga wire to carry a 20a load.

WIRE CURRENT RATINGS

WIRE SIZE AMPERAGE
8 35
10 25
12 20
14 15
16 7
18 5
20 3

 

[huskyfan23]

Well the wire that needed the 20amp fuse is around 16 gauge. This wire is connected to the wiring harness, so do I need to run 16 gauge with the fuse?

 

[DeRocha]

The chart below shows the MAXIMUM amps that can be carried by the wire gauge on the right. If you tap into any wire in you vehicle then you cannot exceed the amp rating for that wire. If you are tapping into a 16 ga wire then you cannot use a fuse higher than 7amps Period!.

That being said, to clarify the instructions requiring you to install a 20a fuse wired to the battery.This means you need to run a 12gauge wire directly to the positive post on the battery, (Not tapping into the existing wiring harness). To make things easier there may be a auxiliary post near the battery that you can tap into. This will be connected to a 8 or 10 gauge wire directly from the + side of the battery.

WIRE SIZE AMPERAGE
amps------ wire size
35-------> 8
25-------> 10
20-------> 12
15-------> 14
7--------> 16
5--------> 18
3--------> 20

 

[huskyfan23]

I've got 8 gauge wiring used on my amps, so could I run the wire from the harness, then put a 20a fuse, and run that to my 8 gauge wiring?

 

[DeRocha]

I don't think you understand correctly. You can only tap into the an existing wire If that wire is 12 gauge or larger (12-8).

Even if the wire is correctly sized you still need to determine its duty load. Example you tap into a 12ga wire used for the door lock/unlock switch. This circuit is protected by a 20A fuse and will draw 15A when the unlock/lock relay is activated. Lets say your amps draw 15A at a high output level. So As you can see if you have the stereo cranking it has placed a 15A load on the Circuit. If you then press the door lock Button the Combined load (15A stereo amp + 15A door lock) would be 30A!. The 20A fuse immediately blows and your door locks and stereo are dead...

Please pm with an e-mail account and I will send you a simplified wiring diagram.

 

[hydroxy]

Just attach the wire to the + lead on the battery, run it through the grommet located right next to the gas pedal, up through your dash to the head unit... Take an hour or so. The wire is only as strong as its weakest link, so just get an equal gauge fuse holder, very simple.

To get the wire through the grommet, use a clothes hanger, straighten it out, attach the wire and poke it through. Do this from the inside, going into the engine area... a lot easier.

ALWAYS go overboard when it comes to wiring. Dont just meet the minimum requirements. You might pay a few bucks extra, but rewiring something is a big PITA, if your car isn't on fire first from fried wires.

Patrick

Here is a very simple chart:

http://paudio.tripod.com/wiregauge.html

 

[huskyfan23]

So how do I do this, Alpine says I need 10 gauge at the battery, but the power wire is around 14-16 gauge. Right now I've got an inline fuse holder with a 20a fuse, with 8 gauge wire running from the power wire in the harness. You're saying this will be a problem?

 

[hydroxy]

hmmm, I'm not an expert, but because I'm assuming that the power cable from the head unit is < 1 foot in length that is why they opted for the higher gauge.

I dont think the way you have it setup should be a problem. I heard that you had like 18guage wire on the fuse holder? that is probably the only problem that there could be. Otherwise, everything sounds in order. Use it till you blow a fuse =P

 

[huskyfan23]

I switched fuse holders, now I have an inline holder that accepts the 8 gauge, so now I have something like 16 gauge from HU to 8 gauge.