An external relay to control power from start switch to activate the starter solenoid is used to take the heavy amp load off the ignition switch. The relay is the only load on the ignition switch when moved to crank position. Relay energizes which puts higher amp load (power) to the starter solenoid. Thereby giving the ignition switch a longer life / better reliability.

I am not sure how they run the ignition coil power when using the external relay.

 

You don't need it but.

Relays are used by some for truck mounted batteries so the heavy gauge battery cable to the starter is only hot when the starter is engaged. Basically the remote relay (sometimes referred to as a FORD Solenoid) energizes the GM solenoid on the GM starter.

Regarding your other relay scenarios. Are you keeping the OEM style fuse box and bulkhead connector set ups? Basically it functions the same as the terminal strips you're contemplating. Separates ACC and IGN on circuits.

 

2 other locations for using relays to keep the higher amp loads off switches are the headlights and the heater fan hi-speed selection.

 

And relays for your fuel pump and cooling fans.

 

Hello All,
Got my 1967 Camaro already to go with a rebuilt LS. Now is the time to wire the car. Since this is a “project of passion” for me I want to do everything from scratch myself. The big problem is I’ve never wired a car from scratch before. I’ve read all the Tony Candela books and done a lot of research online and believe I have everything figure out except a couple of things. These are some very specific things relating to my ignition switch and how things get powered with ACC/ON/START. I know I can make it work but want to know the correct way to do some of this stuff.

• When I switch the key to ACC I will be powering a relay that I need to size based on my current requirements for my accessories. This relay will power a terminal strip where that terminal strip will then power relays for my accessories (i.e. power windows, lights, etc.). When I switch the key to the ON position I will then power on another relay that is sized for everything else (fuel pump, fans, etc.) that will power on a different terminal strip . Am I thinking about that correct?
• I was planning on having the battery in the trunk along with the main fuse and relay panel. Do people usually run wires from the ignition switch from the front of the car to the rear? I was planning on having timeer ignition in the console so I would run the wires down the middle of the car and in to the trunk? I know this seem like a dumb question but I don’t know what people usually do.
• Finally the starter. I have your standard GM#88878289 starter. I keep seeing people put these external starter relay/solenoid in the starter motor circuit. But I thought all newer starters (including this one) has a solenoid bolted to the side of it already. I thought I would just need to tie the START wire from my ignition to the solenoid on the starter. Am I correct? Do I need an additional starter relay?

Thanks for reading through my long winded questions and would appreciate and advice from all you experts in our community. If y’all have any suggested learning material I would love to know. Thanks.

So, I have read your questions a couple times and there are a few things you need to consider.
Having a main ACC relay to a terminal strip is okay for things like radio, amps, interior lights…
what I would remind you is that the largest amp draw components need to have their own relays and ground wires. Things like your fuel pump needs to be connected to a ACC that stays hot when cranking so the fuel pump stays on along with the hot to your ignition system. Your headlights should be on a separate relay setup so they draw power directly from the battery, also with delicate grounds to the battery.

I am not sure that running wires down the trans tunnel will work for a couple reasons,

1.If the battery is in the trunk you will need to run a positive and neg 0 ga or 1 ga wire from the trunk to the starter and the block. This might be hard to hide undear the carpet.

2. The way the rear seat is latched in it could cause wear on the wiring over time. I would stick with the wire channels on each side. Don’t forget you will need to get the alternator charging wire run to the back to the battery so the battery gets charged. This too will need to be a heavy gauge wire to handle the 100+ amp alternator to power everything. Remember while the car is running it gets its power from the alternator so make sure you go big. If you will have a LS with a computer, power windows, radio and audio amps, headlights, heater fan, cooling fans the amperage adds up quickly and plan as if you had all these things on at once.

As far as having a solenoid relay in the trunk gives you a key safety feature and security feature. The solenoid will only supply power to your positive cable running through you car when you are starting the car, otherwise the positive cable has no power. You can also wire the solenoid so you have a cut off switch that is locked in the trunk.

There is a lot to consider and a lot to plan out, good luck and take your time.

just my 2 cents,

Joe

 

Thanks for the info Joe. So you would have your fuel pump connected to ACC as opposed to the ON position? Figured that ACC would be for the radio and maybe power windows and the ON would be for fuel pump, electric fans, etc.

 

On the ignition circuits I would only have what needs power to get the car to run on that output of the ignition key.

You don't need the cooling fans to be on or the AC system, nor or the wipers, and such when starting the car and you just want the least amount of things on while cranking it over so the least amount of power is getting pulled out of the battery setup. Once the car fires up, then the alternator should take over.

As far as relays, get ones that are made for use 24/7. Some relays do not like being on for a long drive of a couple of hours and the activation coils burn out while other relays are fine being used non stop.

On my custom car I have the ignition switch on the column being powered off of a smaller than original wire gauge and fused at the battery in the trunk and then have the outputs of the switch going to 3 main relays in the trunk. One relay gets activated off of the accessory position of the key switch, another is activated off of the ignition output of the key switch and yet another for the crank or starter output on the key switch. I did have to run a dedicated memory wire for the radio to the battery in the trunk but then put a fuse on it back there also.

On my car I also added a 4th relay and this is for the alternator output wire. The reason for adding this relay was so when the key is off, the output wire is dead to where if I'm cleaning or wrenching in that area I don't have to worry about a live terminal or wire. Being in stereo competitions years ago I also have a toggle switch on the alternator relay to where I can check for any alternator noise through the system. By turning the relay on or off I can check for any alternator noise getting added into the audio system.

I also added a bunch more fusing too so that if for example one door popper shorts or blows it's fuse, the other side protected by it's own fuse will not be blown keeping it alive. I did the same with a dedicated fuse for the brake lights, another for the dome lights, another for the map lights, and such and by doing so it does at to the wiring but also makes it easier to track down possible issues.

Jim

 

On the ignition circuits I would only have what needs power to get the car to run on that output of the ignition key.

You don't need the cooling fans to be on or the AC system, nor or the wipers, and such when starting the car and you just want the least amount of things on while cranking it over so the least amount of power is getting pulled out of the battery setup. Once the car fires up, then the alternator should take over.

As far as relays, get ones that are made for use 24/7. Some relays do not like being on for a long drive of a couple of hours and the activation coils burn out while other relays are fine being used non stop.

On my custom car I have the ignition switch on the column being powered off of a smaller than original wire gauge and fused at the battery in the trunk and then have the outputs of the switch going to 3 main relays in the trunk. One relay gets activated off of the accessory position of the key switch, another is activated off of the ignition output of the key switch and yet another for the crank or starter output on the key switch. I did have to run a dedicated memory wire for the radio to the battery in the trunk but then put a fuse on it back there also.

On my car I also added a 4th relay and this is for the alternator output wire. The reason for adding this relay was so when the key is off, the output wire is dead to where if I'm cleaning or wrenching in that area I don't have to worry about a live terminal or wire. Being in stereo competitions years ago I also have a toggle switch on the alternator relay to where I can check for any alternator noise through the system. By turning the relay on or off I can check for any alternator noise getting added into the audio system.

I also added a bunch more fusing too so that if for example one door popper shorts or blows it's fuse, the other side protected by it's own fuse will not be blown keeping it alive. I did the same with a dedicated fuse for the brake lights, another for the dome lights, another for the map lights, and such and by doing so it does at to the wiring but also makes it easier to track down possible issues.

Jim

Wow. thanks for the info Jim. That's a lot of good information. Do you know of any specific relays that like being energized for a long time? I haven't seen any fuses with a duty cycle of 24/7.

 

You can buy a wiring harness that is premade from vendors like American Autowire or Painless Performance.

American Autowire has a classic update kit for a 1967 Camaro Restomod type car. You could use this harness to wire most of your car. The premade harness will energize the LS engine electronics, that would be a separate system, when you turn the key.

 

if you’re going to do it all from scratch correctly the first time

Easiest most bullet proof way we’ve done it for LS is to use a Chevy Connect and Cruise Harness for the LS, only wires necessary to hook up is the key on power and check engine light.

LS3 Engine Controller Kit

Check out the deal on LS3 Engine Controller Kit at GM Performance Motor

www.gmperformancemotor.com

Then install an American auto wire kit for the rest of the car.

Classic Update Kit - 1969 Chevy Camaro

Classic Update Kit - 1969 Chevy Camaro

www.americanautowire.com

buy the expensive wire crimpers that AAW recommends

We also install the complete ground kit from AAW. It essentially connects all of the electronics to solid grounds and the negative post of the battery. The car body is not a good ground for items such as the engine computer and electronic fuel pump. You would be surprised how having solid grounds makes everything work better.

All Copper Grounding Kit

All Copper Grounding Kit

www.americanautowire.com

Using relays and power strips and designing all new circuits is unnecessary work, with the AAW kit all circuits are fused and independent already and built in.

also use AAW heavy duty gauge power wire kit to connect the battery.

Every car we’ve done like this has had zero electrical issues, starts right up, and everything works great.

I see many people recommend soldering each connection, that is unnecessary work if you have the correct crimpers and connectors.

High quality results for the least amount of time.