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Old 05-31-2005, 04:55 PM
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Basic fuse block rewiring

Iím looking for ideas and input in rewiring my car. Nope, its not a hodrod. It will be a track car ( so there are actually very few features I need to keep. Itís a í95 Firebird.
I have two main wiring circuits the engine harness and the interior harness. I think I have figured out what I will do with the engine harness, itís the interior that Iím wondering about.
I plan on keeping
rear brake lights only (no other lights)
Windshield wipers
Stock gauge cluster for speedo, tach, ammeter, and oil pressure

I plan on removing most everything else
Windows, lights, ABS, radio, locks,
Ignition switch (factory), ignition cylinder,
Wiper/CC stalk, etc.

I would like to install
A switch for Ignition (IGN)
Switch for wipers
Starter button
Fuel pump
Fuse blocks (for above and other various items)

The fuse blocks would have fuses for everthing I wire into them
(wipers, rear lights, gauge cluster, additional gauges, PCM power, etc). I plan on one being hot at all times, and one hot on ignition (turned on by IGN switch).
Do I need to use a relay for this fuse block or can I wire the power feed directly to the fuse block through the IGN switch? Is that too much current for the IGN switch? I would think the brake lights and wiper motor would draw too much current for the IGN switch. I suppose I could have a different Ďruní switch with a relay for the hot on ignition fuse block and instead wire the ignition to the hot at all times fuse block but use a different switch.

Removing the steering column parts will require me to use a different multi way switch or potentiometer for the wipers. I want to use my current headlight switch for the wiper switch after I gut the lights. Would this work? Is this a simple 3 position potentiometer? I expect Iíd have to back probe to find out which wires to use as. Maybe use just the dimmer switch?


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Old 05-31-2005, 06:47 PM
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Basic Bare Bones Wiring

Doc here,

Thanks for the Complete info it really helps!

First, what kind of track racing are you planning on doing? Different aspects of racing require Different rules..check to see what the rules say before you start, and make sure you can comply.

You will need (since almost all forms of racing require this) a Battery disconnect switch, located at or very near the battery. just run the positive cable to the high side of the switch, and the Vehicle to the switched side.

From there you will need the heavy cable going to the starter, and 3 fusible for the Ignition circuit, one for the Alternator circuit, and one for the "Hot At all times" circuit.

Feed your Ignition main power from the fuse link (usually 10 gauge pink or purple). From the "ON" side of the switch, run switch power to a properly sized , Buss side of a fuse buss, from that same side, run power for the Coil or HEI whatever you happen to be that it has power whenever you have the key on..(or you COULD fuse it..but for racing I donno...hate to pop a fuse on a random spur or spike while racing and have to sit on the track with a no spark condition..)

(also if required you may want to add a quick disconnect plug on the steering wheel, which will consist of 2- 1/4 inch mono male and female phone plug, and 2 YoYo cords,like a guitar amp wire, with shorted male plug on one end, and the rest of the cord to will attach to your fire-suit.)This way if you are thrown out of the vehicle..the engine will stop running.(usually required.)

Run the "S" side of the Ignition (usually the brown or white wire ) to the "S" terminal on the starter solenoid. From there, find the "I" terminal, (secondary Ignition) and run it to the ignition resistor..or Coil power. This should give you a fully functioning start system.

Are you using a one wire Alternator? If so, run main power back to your fusible link provided for that at the battery buss, otherwise leave the other two wires at the alternator in tact and run main power back to the buss..This should give you a fully functioning charge system..with link protection.

Next run your "I" terminals of all the gauges you intend to use to the low (fused side) of the Ignition Buss. Properly mark and fuse those.

Are your Wipers Electronically switched?

you need to determine that..

older General Mystery cars used Ground to switch the speed function at the wiper motor / washer If you have one of these, the motor will be wired "Hot in Run at all times" and have 3 switchable grounds..

If you have one of these, all you need is a 3 position Switch of comparable current handling capabilities to control it...the head light-switch won't work...(unless you ground one side of it, and use only high speed)

The dimmer rheostat may be geared for electronic dimming (Darlington pair transistors) in any case would probably burn it out attempting to speed control a motor with it.

If it's electronic, you need to determine the type of speed switching, (power or Ground) and install a comparable switch to handle that. (center wiper to either ground or power, terminals 1, 2,and 3 out to the circuit card.) Run the Power wire back to your "Ign" fuse buss and mark and properly fuse it.

Locate your PCM power wire and run that to your Ignition terminal and properly mark and fuse that...Then isolate the memory wire, and run that to your "Hot at all times " buss, properly fuse and mark it.

Set up your Switch panel (I assume you already have a layout plan for this) install your wiper fuel pump switch and any other Variable you may require here, run each (high side ) to a proper fuse on the "Ign" Buss, and mark accordingly..

For your fuel pump, I assume your using a high volume pump..(which means high current) use a relay, run your control circuit to your switch at your switch panel..then using 10 gauge wire, wire the contacts from the "Hot at all times" buss, with a proper fuse, then the other side to the pump. (you might want to consider putting it on the Ignition side, using the switch for bypass only, to prevent unnecessary troubleshooting on start up because the switch is off) just a thought...but it has happened to me before...

As for the brake lights, I would wire them "HOT at all times" through the hot buss and a proper fuse...for two good reasons...Pushing or towing...or anything that might require movement of the vehicle with the engine off...Simply run a proper gauge wire from your "hot at all times" fuse buss, to one side of the brake light switch, the other side will remain the same.

You CAN run relays For the Fuse busses, and it certainly will deliver more current to the buss..but since your running Virtually no Current at the busses, If the buss size is properly gauged, you should have no problem running without one..The Ignition Switch in stock configuration handles more current than your planning to run through it..

However, Fire safety and more current delivered will result in using a relay.

Good safe rule of thumb..Use a Relay on anything over 20 amps, any motor,

(rotor locks can cause major Multiples of current draw over stock run draw..IE a motor drawing 30 amps, free wheeling then gets the rotor stuck, like a plastic bag in a fan..might well draw 60 or 80 amps to try to overcome the lock.resulting in a burned up harness or worse...)

And any run of extended length of will deliver more source current to the device and generate less heat in the wire...AND anything you just don't feel right about drawing a load! Never hurts to overprotect!

I answered your post here doing this in my mind,not on if it's a bit scattered , or I missed or omitted something, sorry 'bout that..just trying to lay down the basics..just ask again!

You do know painless and EZ make "Bare Bones" Harnesses to achieve the same thing your trying to do for like under $200?? You might want to consider that road and add in the racing specialty's to that..just a thought...

Hope that gives you some basic direction..

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Old 06-02-2005, 06:46 PM
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Doc, Thanks for the reply. Very informative. It is more or less what I want to do but with the details I need.

I'm building a 'road race' car, not a drag racer. The rules are pretty much open on wiring except for the requirement of a main switch which includes a secondary switch for the alternator. I'm going to start pruning the harness very soon. With a little more planning I'm going to tackle the rest of the wiring, adding fuse blocks, ign switch, etc as well as finish gutting the interior this month.

I'm not sure if my wipers are electonically switched or not, I'll have to go back and look at the factory service manual. I've beens studying those pretty good. Two big issues with this car is that its an LT1 w/ an opti spark and it has VATS. I already have a module to simulate the fuel enable signal to the PCM but its not installed yet.

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