Car Wiring Newb (Ignition and other Fuses)

[thapranksta]

I'm adding new accessories to my Gen 5 pretty soon . I need to know if there is a fuse especially for accessories (an auxillary fuse or something) that I could use that gives power when the car is turned on instead of tapping directly into the ignition wire. It sorta gives me more piece of mind not going directly to the ignition.

I've already done one install of an auto-dim mirror which goes directly to the ignition. Thanks and remember to be gentle.

[hooRAH]

Look in the owners manual for the fuse listing. There won't be any unused fuses, but you can pull off of one you that you calculate can handle the load. Alternatively, you can try to use the fuse that the equipment was originally intended for.

For example, say you don't have power locks. If the manual says "Fuse 16 is for power locks (if equipped)" that would be a good place to pull power from.

[thapranksta]

So in that case would I really need the fuse that came with the accessory I added if the power is being tapped from an unused source anyway?


Edit: Also, when you mention load are you referring to voltage (12V)?

[hooRAH]

Originally Posted by thapranksta

So in that case would I really need the fuse that came with the accessory I added if the power is being tapped from an unused source anyway?

All of the power comes from the same place, it just gets split up into different fuses so that if one system goes, it doesn't take everything down with it. There should not be any unused fuses. A typical list of features would be the radio, cigarette lighter, and dash lights on one fuse. If the car for whatever reason didn't come with a radio, the cigarette lighter and dash lights would still use that fuse.

If your car, for example, had an 8 amp fuse for the radio, cigarette lighter, and dash lights, but your car didn't have a radio, you'd be just fine putting the radio on that fuse, because its already rated for it. That way, you don't have to calculate if the circuit can handle the load (by picking some random fuse).

Edit: Also, when you mention load are you referring to voltage (12V)?

The load of a device is measured in watts. Because you can assume that everything is 12V, you can remove the voltage from your analysis and measure load carrying capability in amperage (amps, A). Fuses are rated in amps.

If, for whatever reason, you had a bare wire straight from the battery, and you wanted to put a fuse on it, you could determine the amperage requirement to operate the device, and put that size fuse in the line. You would have a one device circuit all on its own. This is really unneccessary, because unless you're putting in a blender in your dash, all of the options have already been accounted for at one point in the engineering of the wiring system. You just have to find out where.

Volts * Amps = Watts

[hooRAH]

Originally Posted by thapranksta

So in that case would I really need the fuse that came with the accessory I added if the power is being tapped from an unused source anyway?


Edit: Also, when you mention load are you referring to voltage (12V)?

Ahh I put my reply in your quote and it didn't show up right. For some reason, I can't edit it either. Here's my reply to the first part of your post.

All of the power comes from the same place, it just gets split up into different fuses so that if one system goes, it doesn't take everything down with it. There should not be any unused fuses. A typical list of features would be the radio, cigarette lighter, and dash lights on one fuse. If the car for whatever reason didn't come with a radio, the cigarette lighter and dash lights would still use that fuse.

If your car, for example, had an 8 amp fuse for the radio, cigarette lighter, and dash lights, but your car didn't have a radio, you'd be just fine putting the radio on that fuse, because its already rated for it. That way, you don't have to calculate if the circuit can handle the load (by picking some random fuse).

[thapranksta]

Originally Posted by hooRAH

The load of a device is measured in watts. Because you can assume that everything is 12V, you can remove the voltage from your analysis and measure load carrying capability in amperage (amps, A). Fuses are rated in amps.

If, for whatever reason, you had a bare wire straight from the battery, and you wanted to put a fuse on it, you could determine the amperage requirement to operate the device, and put that size fuse in the line. You would have a one device circuit all on its own. This is really unneccessary, because unless you're putting in a blender in your dash, all of the options have already been accounted for at one point in the engineering of the wiring system. You just have to find out where.

Volts * Amps = Watts

I'm thinking about seat heaters right now while the weather is hot so I can get a good discount. No, not running straight from the battery. I know fuses are rated in amps. And now that you mention it, I remember that volts * amps equation from physics class. OK, so I understand this much.

[thapranksta]

What guage are the wires leading to the fuse box?

Also, I took a look at my fuse box and there is a fuse for seat heaters but I don't have any seat heaters installed.

[hooRAH]

Originally Posted by thapranksta

What guage are the wires leading to the fuse box?

Also, I took a look at my fuse box and there is a fuse for seat heaters but I don't have any seat heaters installed.

Thats the fuse you should use then.

[thapranksta]

So would the factory seat heater fuse get power only when the ignition is on or would it not get any power because there is no factory trigger for it? Excuse me if I'm asking dumb questions. But if I were to install a seat heater, then I would want to make sure that if I forgot to turn it off that it would turn off when the ignition is turned off.

BTW, thanks for the help thus far.

[hooRAH]

Originally Posted by thapranksta

So would the factory seat heater fuse get power only when the ignition is on or would it not get any power because there is no factory trigger for it? Excuse me if I'm asking dumb questions. But if I were to install a seat heater, then I would want to make sure that if I forgot to turn it off that it would turn off when the ignition is turned off.

BTW, thanks for the help thus far.

Yes, it should only get power when the car ignition is on.

[thapranksta]

What guage are the wires running to the fuse box?

[Mid Life Crisis]

I have a ton of extra accessories plugged into the electrical system, and the easiest way to do what you are looking for is take off the center console cover & splice directly into the cigarette lighter. May not be very technical, but it will get the job done!

[88 LE]

Originally Posted by thapranksta

So would the factory seat heater fuse get power only when the ignition is on or would it not get any power because there is no factory trigger for it?

Get yourself a DMM and measure the output at the fuse socket. Measure both sides of the fuse socket with the ignition on and off.

That'll tell you if theres power running to that fuse socket and if its constant or switched (live only when the ignition is on).



Personally I wouldn't tap into a fuse box, unused circuit or not. But what you do on your car is up to you.

[thapranksta]

Originally Posted by 88 LE

Get yourself a DMM and measure the output at the fuse socket. Measure both sides of the fuse socket with the ignition on and off.

That'll tell you if theres power running to that fuse socket and if its constant or switched (live only when the ignition is on).



Personally I wouldn't tap into a fuse box, unused circuit or not. But what you do on your car is up to you.

What would you do then?

[88 LE]

^ I would use a relay.