Vintage Mustang Forums banner

1 - 8 of 8 Posts

·
Registered
Joined
·
6,630 Posts
Discussion Starter #1
So currently im looking at running 60/55W bulbs. First, is this a good wattage to run, or should i run one with a 100w high beam or..??? Also, I'm thinking of running the euro spec pattern because of the nice cut-off.

-- Wires -----------
So people say run 12 AWG. Is this 12 AWG for the primary powering/grounding BOTH bulbs? As in, half of the current through this wire goes to one bulb, and one to the other? Or is this a large enough wire for ONE bulb? I'm planning on splitting it once i get to the first headlight down to smaller gauge, but... now that I think about it... that would require another fuse to be safe, maybe ill just run 12awg to both.

--Fuses------------------
So the way I figure it, i will have 2 relays, so i need 2 fuses near the power source. 120watts (2x60) for each circuit, ~ 10 A, so I should run something like a 15A fuse before each relay (which is WELL within the range of that wire), right?
 

·
Registered
Joined
·
6,630 Posts
Discussion Starter #3
I know plenty about ohms law to be more than dangerous (i just finished learning models for MOS and bipolar transistor amplifier circuits.. i get electricty).

I'm just a little stumped on the details of how people came to think we should use 12 gauge wire for headlamps (yes i get that it will drop less voltage), and what fuse I should use. I figured I would check my analysis with the experienced bunch.
 

·
Registered
Joined
·
520 Posts
The only reason to run larger guage wire is voltage drop. As you probably already know from Ohm's law, resistance increases as voltage decreases. (Which is why power transmission lines are such high voltage) You are correct in assuming 12 guage wire is probably overkill for the application since your wiring is very short. 14 guage is more than sufficent for this application.

Also don't use a fuse in a headlamp circuit. It is potentially deadly and against the law in most states. (Though I have never had anyone actually check in a saftey inspection) Use a headlamp circuit breaker instead. I like the kind that plug into a standard blade type fuse holder. They are about three bucks at AutoZone. Unless you plan on running your low beams and hi beams at the same time, you can use a single breaker.
 

·
Registered
Joined
·
7,294 Posts
Also don't use a fuse in a headlamp circuit. It is potentially deadly and against the law in most states. (Though I have never had anyone actually check in a saftey inspection) Use a headlamp circuit breaker instead. I like the kind that plug into a standard blade type fuse holder. They are about three bucks at AutoZone. Unless you plan on running your low beams and hi beams at the same time, you can use a single breaker.
Now that is some good info! I'm getting ready to relay-ize a GM truck (which run hi&low concurrently when modified) and just about used a fuse. The how-to I read for it reccomended 10AWG, which is probably overkill. The guy wasn't the smartest though, as some of his other advice included NOT running a fuse/protection device. That's stupid; running highs & lows plus near-HID bulbs, if the relays screw up, they'll probably weld themselves together and roast the wimpy stock wiring that everything's hooked into :horror: I'll definatley pick up a circutbreaker.
thanks
--kyle
 

·
Premium Member
Joined
·
19,203 Posts
Also don't use a fuse in a headlamp circuit. It is potentially deadly and against the law in most states. (Though I have never had anyone actually check in a saftey inspection)
Can you explain why this is potentially deadly and against the law? The only difference between a circuit breaker and a fuse is that a fuse is a one-time use. Having headlights out due to a blown fuse is no different than busted headlamp bulbs.
 

·
Registered
Joined
·
6,630 Posts
Discussion Starter #7
Actually, i think i should make a point to run SEPERATE protection for your highs and lows. That way, if one guys, you just hit the highbeam switch and you have a working circuit still!
 

·
Registered
Joined
·
520 Posts
Afuse will just blow, the circuit breaker will reset in about three seconds and give some light. (sort of like a turn signal) This will give you a chance to stop. I actually had this happen to me in an old truck. I was driving on a curvy country road and had the headlamp fuse blow going into a double "S" curve. Everything went pitch black (no street lights, no nothing). I slammed on the brakes as hard as I could without going into a skid and guessed where the curves were. I came to rest in the ditch about a foot and half from a giant oak tree. The next day, I cleaned the seat and fixed the headlights. :eek:
 
1 - 8 of 8 Posts
Top