wiring from scratch 93 mustang

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URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=121421
Printed Date: July 21, 2025 at 4:30 AM

Topic: wiring from scratch 93 mustang

Posted By: bjamick
Subject: wiring from scratch 93 mustang
Date Posted: April 19, 2010 at 2:16 PM

Ok guys looking for a little help here. I think I've got it down but I want to make sure I've got things at least sorted out.

Here is a wiring diagram I just made for the firewall forward. I want to make sure I've got it right before I move to far.

I've also gotta make a wiring diagram for the firewall back also. Some things I'm not for sure on, is how to wire up the running lights. Like when I turn on the headlights I want the lights to come on in the back like normal, then light up brighter when I hit the brake. I'm not exactly for sure how to do that.

I'm also not exactly for sure what size wire to run, because I really don't know how many amps this stuff pulls. I know I'm going to run welding cable from the battery to the alternator, then probably a 6 to the starter, and another 6 to the power distribution block. Everything else I'm guessing will probably be 16 gauge.

I've got wiring diagrams on my mustang, like the headlights were only on a 15a fuse. Yet on another site, it shows headlights pull like 50+ amps on high.

Anyways guys I'm looking for some help. I'm going to be gutting all the wiring out of the car, but I will be using the factory connectors on everything. I'm just going to be leaving like 5" of wire connected to it.

I'm looking at what all I can consolidate for the body harness?

Like headlights, blinkers, brake lights on one 20A fuse
Wiper motor and dome light on one 15A fuse. Etc!

I was hoping I could squeeze everything into 4 fuses.

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93 mustang coupe

Replies:

Posted By: Ween
Date Posted: April 19, 2010 at 2:32 PM

hi,

for the rear lights, to keep it simple, use a dual filament bulb.

to get an idea of what a particular item draws, check owners manuals (fuses section) and/or fuse box labels.

going oversize on wiring gauge reduces voltage drop, but increases weight.

a wiring diagram manual may show gauge sizes used on particular circuits.

if you consolidate too many circuits on one fuse, and have a failure in the wiring.. i.e. short circuit, you'll probably lose all operation of all circuits on that fuse.

Posted By: bjamick
Date Posted: April 19, 2010 at 5:25 PM

This is the fuse box for my car. See they have alot of things running off one fuse. I was hoping to do the same with mine. Except I will only be running a couple things mostly. Really all I want is:

Headlights (high/low)
blinkers
Brake lights
Dome light
radio
The lights in my autometer gauges to work.
Original Ignition switch.
Bottle warmer
Also maybe a light for my shifter.

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93 mustang coupe

Posted By: Ween
Date Posted: April 19, 2010 at 6:44 PM

remember the fuse is to protect the wire, the load comes second...so

Headlamps...if the switch is only controlling the relay coils, a 3 amp fuse is fine. 18 ga to the relay coils. 16 ga on the contacts.\

Turn Signals.. 15 amp fuse, 16 ga wire.

Brake Lamps.. 15 amp fuse, 16 ga wire.

Tail/Parking Lamps.. 10 amp fuse, 16 ga wire.

Dome Lamp.. 15 amp fuse, 18 ga wire.

Radio.. 2 Circuits.. Accessory power 5 amp fuse, 18 ga wire. Battery power, use dome lamp fuse, 16 ga wire.

Gauge Illumination.. 5 amp fuse, 18 ga wire.

Ignition Switch.. 30 amp fuses, 10 or 12 ga wire.\

Bottle Warmer.. depends on power draw 15 amp fuse? 16 ga wire 20 amp fuse? 14 ga wire

Shifter light.. connect to parking lights or radio accessory... fuse value can remain the same.

Posted By: bjamick
Date Posted: April 19, 2010 at 8:08 PM

I guess do each thing on it's own circuit to make things easier when something happens? So I need like a 10 circuit fuse box then to cover the body. The engine will have it's own fuse box. Thanks a lot for your help, it really helps out.

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93 mustang coupe

Posted By: bjamick
Date Posted: April 20, 2010 at 9:10 AM

On my diagram, where would the fuse for the ignition switch go exactly? Would it be smarter to do a fusible link? Also which side of the ign switch should I put it at? In between the fuse box and switch, or the power distribution box to the switch?

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93 mustang coupe

Posted By: Ween
Date Posted: April 20, 2010 at 12:56 PM

use one or two of the fuses at the power distribution block for the fused power to the ignition switch. the outputs of the ignition switch would then go to your interior fuse box, distributing from there.

Posted By: oldspark
Date Posted: April 20, 2010 at 9:59 PM

Self-resetting circuit breakers may be best for the lighting as well - especially if you have a single point of failure (SPOF) as depicted above (ie - all headlight power from a distro-box single feed; and the switch's fuse).

I have hi & low separately fused (actually, $7 "blade type" circuit breakers, and one for each beam = 2 x lo & 2 x hi; fed via one large "master" flink).
And the hi-beam flasher/overtaking switch is on a separate fuse to the beam & hi/lo switch so I have redundancy in case of emergency. This will power another fused relay to the hi-beams (to bypass the above SPOF flink).