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Electrically Inclined. . .or is it declined?

DEV1ST8R

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DEV1ST8R Enthusiast

DEV1ST8R

Posted
Posted

I have a basic question about wiring... I know how to wire stuff up, but it's always been with pre-included wires. What AWG wiring is best for 12v/automotive applications? Particularly, if adding an additional turn signal or brake light? And the same wires go for foglights?

 

I'm looking at adding turn signals on or near my side mirrors, does anyone happen to know a good place to tap into for both the driver and passenger sides?

 

THANKS!

 

:chevy:

Yukon04 Enthusiast

Yukon04

Posted
Posted

It depends on how much current the wire will be carrying. 10Ga wire will carry 30A all day long. This seems high for a fog and 14Ga sounds very high for turn signal.

 

I did a quick search in all the GM electrical schematics I have and the typical gauge size for turn signals is 0.50mm^2 or 20Ga wire. Fog lamps are showing the same.

 

Check the fog and turn signal current draw, usually found in a specification for the light. If you are using aftermarket, they may have a larger current draw than the stock ones. Fuse the fog lamps from an ignition relay in the underhood fusepanel (UHBEC). Fuse the turn signals with a any of the headlamp relays in the UHBEC. This should provide you with the closest to OEM you can get without actually using all OEM parts.

 

Fuse accordingly and don't oversize the wires. Best thing to do is determine how much current the light will draw and use the respective wire gauge. There should be charts all over the internet that will tell you use "XX" Ga wire with "XX" amount of current. Oversized wires will result in unnecessary voltage drop. Not a big deal with the turnsignals, but the fog lamps will suffer in performance.

mmmikkke Senior Enthusiast

mmmikkke

Posted
Posted

If you need to convert watts to amps, here's the formula:

 

amps = watts / volts

 

Example:

 

55 watt fog lights

14 v nominal electrical system voltage

 

amps = 55 / 14 = approximately 4 amps.

 

(So two 55 watt fog lights would draw 8 amps.)

Shotgun Enthusiast

Shotgun

Posted
Posted
Fuse accordingly and don't oversize the wires.  Best thing to do is determine how much current the light will draw and use the respective wire gauge.  Oversized wires will result in unnecessary voltage drop.  Not a big deal with the turnsignals, but the fog lamps will suffer in performance.

 

 

 

 

This is exactly opposite of the fact. Increasing wire size reduces voltage drop which is critical on 12VDC systems.Why do some people on the board insist on posting misleading information when they have no clue to what they are posting about? :chevy:

Yukon04 Enthusiast

Yukon04

Posted
Posted
Fuse accordingly and don't oversize the wires.   Best thing to do is determine how much current the light will draw and use the respective wire gauge.  Oversized wires will result in unnecessary voltage drop.  Not a big deal with the turnsignals, but the fog lamps will suffer in performance.

 

 

 

 

This is exactly opposite of the fact. Increasing wire size reduces voltage drop which is critical on 12VDC systems.Why do some people on the board insist on posting misleading information when they have no clue to what they are posting about? :)

 

 

 

 

 

My fault. Long day, bad post. Had the logic backwards. I am kinda familiar with 12V DC systems. Kinda harsh were'nt you?

71GMC_3/4T Enthusiast

71GMC_3/4T

Posted
Posted

Um, BBSilverado, I think you misworded that...

Undersized or a long run causes a voltage drop, oversized doesn't hurt anything except its bigger and heavier.

 

A good rule of thumb (thanks to the late Carl Colson):

14 gauge is good for 15 amps, and it doubles (or halves) for every 3 wire size number changes.

 

It ain't exact, but it will get you very close, with a safety margin.

 

Now, you won't find 17 gauge wire of course, but you can get a good idea what current your wire is capable of carrying. Also, wire is rated in a number of ohms/1000ft typically, and that's where your voltage drop comes in. For example, 14 gauge wire is 2.5 ohms/1000ft. That means it would drop more than 30V over that 1000 ft if it were carrying 15 amps. In 12V systems, that starts to become a problem.

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