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the big electrical wiring question thread!

Old 11-15-08, 10:31 PM
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the big electrical wiring question thread!

hey guys i thought this was the apporiate section since it will be for a race car but im totally confused on the subject, i might be think too much on it or i dont know, so i know theres alot of wiring gurus heres so this will be for everyone to ask questions and what not..

i have searched and searched but i never got a thorough answer,so ill start with my problem,

i have the painless 8 rocker switch panel, and ive seen peolpe use terminal blocks ann relays for the switches how do you wire it up, i have a pic i found but im still not sure how its done or atleast can some explain the pic..




he has the relays wired to the terminal block then to the switch connector im seriously confused how this is done, any one have some inputs similar to this or how they wired their own, i just dont want to have seperate wires for so many switches that it becomes redudant


any info will be great!

alex

Last edited by ivegonemad; 11-15-08 at 10:41 PM.
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Old 11-16-08, 01:30 AM
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Here is the power distribution diagram of a simple racecar that I wired a couple of years ago. When I say simple, I mean simple: the 5 fuses and 4 relays shown in the diagram were the only ones on the car.

Didn't the Painless kit include a suggested wiring diagram? I'm not trying to insult you but if you feel lost this early in the process, you may want to consider hiring someone else to wire the car for you. Wiring mistakes are often difficult to track down and can damage expensive components (for instance: fried ECU or blown engine from one injector cutting out).


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Old 11-16-08, 02:21 AM
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i also forgot to add that if theres any way i can have one switch to turn all the lights(headlights, parking lights, taillights, etc). any ideas?
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Old 11-16-08, 02:47 AM
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Originally Posted by scotty305 View Post
Didn't the Painless kit include a suggested wiring diagram? I'm not trying to insult you but if you feel lost this early in the process, you may want to consider hiring someone else to wire the car for you. Wiring mistakes are often difficult to track down and can damage expensive components (for instance: fried ECU or blown engine from one injector cutting out).
the kit i bought is for the chassis wirring(interior, exterior) and it only came with the manual
ive finished the car as far as just getting the body harness in, my main problem is wiring the switches to the components, but looking at your diagram it makes the relay wiring a bit easier i couldnt figure out what the numbers were(85,86 etc) but now i understand.

none taken, the ECU i know i wont be wiring up, ive saved up too long to get it and to burn it up i wont risk it. on the other i would like to learn more and take the challenge, this is my first so ill just try it now.

so is it just basically having the switches wired in line with the circuit??
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Old 11-16-08, 03:25 PM
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A relay has two parts, a coil (between pins 85-86) and a switch (between 30-87).
When you send power through the coil (by connecting +12V to one pin and GND to the other), the coil acts like an electromagnet and pulls the switch closed. Note that in the diagram I posted, the Ignition switch connects pin 86 of the Ignition Relay to ground, which will cause it to turn on. The ECU will use a "low side driver" or "switched ground circuit" to connect pin 86 of the Fuel relay to ground.


Without relays, you would need thick heavy-duty wires going from the battery to a big heavy-duty switch and then back to the device. For instance, your fan may draw 15-30A of current, which is enough to melt most switches that people install inside cars. Finding a switch to handle 30A isn't impossible, but it would be bulky and expensive.


Part of the reason to use relays is you don't need to run high-power wires near the driver. You can save weight by reducing the length of large wires, especially if you mount the relays near the battery or near the devices that they are controlling. It's also much safer if there is a short somewhere, since the low-power wire between the relay and the switch is unlikely to burn anything. Plus you can use small lightweight switches because the coil (between pins 85-86) doesn't need much power to connect the contacts (30-87). You can use switches rated for only 0.5-1A, which will cost less and weigh less.



You can add another relay and switch to the diagram above for headlights, wire it like this:

Add another fuse (might call this the "Lights" fuse).

"Lights" relay:
Lights (Pin 30) connects to "Lights" fuse
Lights (Pin 85) connects to Ignition Relay (Pin 87), same wire that is connecting to the other relays on Pin 85.
Lights (Pin 86) connects to "Lights" switch, relay will turn ON when switch connects to ground.
Lights (Pin 87) provides power to all of the lights when the "Lights" switch is connected to ground.


Note that if you want your headlights to turn on and off independently of the other lights (like a street car), you will need to add another relay (Headlights relay) and switch (Headlights switch) for that.

Last edited by scotty305; 11-16-08 at 03:29 PM.
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Old 11-17-08, 12:32 PM
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i understand it now, yeah i found the diagrams on painless website so it helped alot, i followed your diagram but ill be adding multiple switches to each component, so ill be working on that and see how it goes...
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