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Hello

i have a sbc in my z.  My wires fried (literally) so I am in the process of re wiring using the painless 21 circuit.  I pulled out all of the original burned harnesses and starting from scratch. Im sure I got some wires crossed but my main concern is relays and the voltage regulator.  

 

1) Do I need to add any relays or is it just an extra precaution.  If I do where would I place them in the wiring.  

2) do I need to wire up the voltage regulator ( by the driver side kick mat). If so, what wires do I use 

3) for the rear brakes where does the third brake light wire go. All other connections seems connected

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1)  Relays....yes.  They are an excellent addition to any high-load circuit in your system.  I integrated relays into my starter, headlight, and running light circuits.  Physically located them on the firewall in the passenger footwell.

 

2)  Voltage regulator....should not need it.  Any SBC in the last 30 years or so had an alternator with integral voltage regulator; and if your engine's older than that, there's a good chance that the alternator was upgraded somewhere along the way to include it.  You can visually inspect the alternator to verify.

 

3)  3rd brake light....have you physically added a third brake light to your car?  If so, then it should be wired into the same circuit as your main brake lights.  If not, that part of the harness is not necessary.  I added a third brake light to my car for safety, like this one:  https://www.allpar.com/reviews/other/LED-third-brake-light.html

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Thank you guys for the quick reply!!!  This forum is awesome.  Regarding the relays...it sounds like it’s more of a added feature and if possible add it everywhere?  Is there a danger of not adding any relays?  I thought I read that the 240z dimmer switch had a relay built in?

 

 

thanks

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22 minutes ago, captainkim said:

Thank you guys for the quick reply!!!  This forum is awesome.  Regarding the relays...it sounds like it’s more of a added feature and if possible add it everywhere?  Is there a danger of not adding any relays?  I thought I read that the 240z dimmer switch had a relay built in?

 

 

thanks

 

The 240z does not have a relay built into the dimmer switch. It is just a a piece of copper that switches between the high and low light circuit.

 

If you examine a 240Z combination switch you will see that the contacts are just small, thin,  pieces of copper bits which  are subjected to heating and pitting from arcing when a high amperage load is supplied. Headlights pull high amps across those metal bits in the switch. 

 

Using relays for the headlights takes the high amp load off of the wiring and those copper contacts inside the switch.

 

For over 40 years Z owners have reported having their combination switch melt due to high amp loads.

 

So yes headlight relays are a good idea.

 

Many Painless harnesses have been installed in Z cars so it is likely that there is a relay write up on HybridZ or at ClassicZcars.com.

 

Benefits of headlight relays:

  • Less stress on wiring and the combo switch
  • The lights get a full 12 volts
  • You can run higher amperage headlights such as H4s etc

Note: A relay for the electric fuel pump is also a good idea.

 

 

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i thought I was good to move on to relays but my ignition wiring is not working now.   i have a SBC so i used the painless wiring for GM 10101.   ON the ignition section , they have 2 hot wires (red) and 2 purple  (see below).   The ignition column only has 5 slots (behind the key)....Would anyone know the correct wiring for ignition?  Do i need to join some wires together?  Ive looked all over and most links are no longer valid.   Any pics or responses are GREATLY appreciated.   This wiring is driving me bonkers and have me second guessing everything

 

This is how the reference book is showing.

 

RED: (2) 12 gauge wires, printed [IGNITION SWITCH SECTION] #934 TO IGNITION SWITCH (POWER B+), these wires come from a buss bar on the fuse block and feed battery power to the ignition switch. These wires have power at all times. 10102 & 10104 only has one RED #934 wire.

 

ORANGE: 12 gauge wire, printed [IGNITION SWITCH SECTION] #933 TO IGNITION SWITCH “IGN”, this wire provides the switched power source to the fuse block. This wire powers all of the switched power circuits to the harness with the exception of the RADIO fuse. This wire only has power when the ignition switch is in the ON/RUN position.

 

PINK: 14 gauge wire, printed [IGNITION SWITCH SECTION] #931 TO IGNITION SWITCH (COIL IGN), this wire provides power from the ignition switch to the 30 amp COIL fuse on the fuse block. This wire has power when the ignition switch is in the ON/RUN position as well as the START position.

 

PURPLE: 12 gauge wire, NEUTRAL SAFETY SWITCH, this wire sends power to the neutral safety switch and only has power when the ignition switch is in the START position. Kits 10101 & 10103 will have 2 PURPLE wires: one going from the ign. switch connector to the NSS and the other leading from the NSS to the starter solenoid. Kits 10102 & 10104 only have a single wire printed [ENGINE SECTION A] #919 TO STARTER SOLENOID.

 

BROWN: 12 gauge wire, printed [IGNITION SWITCH SECTION] TO IGNITION SWITCH ACC, this wire carries power to the RADIO fuse on the fuse block. This BROWN wire has power when the ignition is in the ACCESSORY position and when in the ON/RUN position.

 

 

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Could the orange wire be for accessaries you want on with the engine off and the pink wire powers the ignition circuit.

 

On the back of  the ignition switch are there separate terminals for ACC and IGN?

 

 

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Captain, download a wiring diagram for your year Datsun Z, as they change slightly with the models and year to year.  Also look at the Painless manual and match up where their colors go compared to the locations of the Z.  If you indeed bought the whole wiring 21 circuit, you will definitely need the Datsun wiring diagram to reference on how to hook up your wiring thru out the car, beyond just your ignition circuit.

 

I personal went the other way.  Mine is a 1975 that I am keeping fairly stock, but gutting unnecessary items to run as an autocross car.  I am using the stock wiring harness, but had to reference the wiring diagram to see what circuits I could remove and how to route certain wiring to a new fuse box I am installing, for the light circuits.

 

What I am trying to say is, you are wanting a full answer, but giving us half the initial information.  So provide all the info of your vehicle and download both Datsun and Painless manuals and wiring diagrams. 

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Thanks everyone for the response.  I have done all of the above mentioned and am finally looking at the schematics. Even still, it seems like some wires need to be connected together like the front and rear parking lights etc.  I’m in the process of trying make sense of all the different sources into one.  

 

I follwed the pics a few days back and then saw another that has it another way.  I’ll figure it out. I have everything.  Just have to follow the lines and hope I. Can correctly match it 

 

 

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