Ez wiring help

[Mr.Hyde]

Hey guys a have a few questions about the 12 circuit ezwiring harness and was wondering if someone can help me out? The truck is a 1968 c10 283 three on the tree no ac lwb.

Ok first off, the marker light are wired to the front lights in the grille. Now what I'm wondering is if I can splice off these and use them to power my side markers aswell and then side markers to ground?.

Second it seems like the wiring harness infact did not come with a dome light circuit.. How am I supposed to wire this up? I'm not using my third brake circuit can I just go off of this? And I don't seem to see a spot where the courtesy light switch would go in the door?

Finally I read the neutral safety switch directions and the ones on the wiring diagrams and just can't figure it out.

[VetteVet]

Originally Posted by Mr.Hyde

Hey guys a have a few questions about the 12 circuit ezwiring harness and was wondering if someone can help me out? The truck is a 1968 c10 283 three on the tree no ac lwb.

Ok first off, the marker light are wired to the front lights in the grille. Now what I'm wondering is if I can splice off these and use them to power my side markers aswell and then side markers to ground?.

Yes you can. Here's the diagram. It shows the wiring in the upper right. The outside lights are the park/turn lights. The next two are your markers. Notice the brown wires feed both sets of lights for the park lights and the markers, which are then grounded. I was under the impression that the 68s didn't come with markers, just the lenses for the fenders.





Second it seems like the wiring harness infact did not come with a dome light circuit.. How am I supposed to wire this up? I'm not using my third brake circuit can I just go off of this? And I don't seem to see a spot where the courtesy light switch would go in the door?

The dome light is fed by an orange wire off the dome light fuse in the fuse panel. It runs straight to the dome light and or any courtesy lights. The ground wires are the switched wires for the light/s. The ground wires run from the dome light to the door jamb switches and to the headlight switch terminal that is grounded when the HL switch is turned all the way C/W. IIRC. I don't believe the 68 came with anything but the dome light.

Finally I read the neutral safety switch directions and the ones on the wiring diagrams and just can't figure it out.

The neutral switch has four terminals on it, two are for the backup lights (green) and two are for the purple wire from the key switch to the starter solenoid. The purple wire from the key switch is plugged into the two vertical terminals on the NSS. Also in the plug is the other purple wire that runs to the firewall connection, then through the firewall to the solenoid.

The Nss mounts on the topside of the steering column just a few inches from the firewall. It mounts over a cutout in the column with a couple of short screws.

[Mr.Hyde]

Hmm the ezwiring says they circuit would be labeled and and don't remember seeing a fuse location designated dome.

[Mr.Hyde]

Ok so I've come to the realization I'm Terrible at wiring and need more help then I should. I guess I'm just concerned about burning down 3 years of work... I mean I've searched on this forum for info and can't find simple explanations. So I ask the gurus please help! Tell me what info you need to help me and I'll do my best to get it. Need help on a guage cluster what wires go where on the gang plug, done wiring I don't have a dome circuit, I think I have the headlight switch figured out confirmation would be nice if that's possible, umm the neutral safer switch I kind of get but not 100%... I've seen the pictures of the ignition switch and headlight but when Unlabeled mean nothing to me.. And I will come brine to try and figure out the heater and wiper wiring.. I can't lose another project because I don't understand wiring...

[_Ogre]

once your truck is wired, you will have intimate knowledge of your truck wiring
as long as everything is fused, there is minimal chance of catching fire

I don't have a dome circuit

not sure if your 12 circuit mini has a separate dome fuse
come off the brake circuit like the stock 68, run a hot wire to the dome light and the ground wire from the dome light back to the dome ground on the headlight switch

here is a 68 headlight switch posted in another thread by vetvette
the white dome/courtesy ground is obviously the dome ground
and the (infamous) orange wire is actually fed off the brake light fuse, branching off to the dome light
the orange wire also powers half the headlight switch for the brown wire: parking, side marker, license plate lights



ask separate questions in this thread. your paragraph above is a little jumbled up

[_Ogre]

I think I have the headlight switch figured out confirmation would be nice if that's possible

as long as you have power to the red and orange wires the switch should work fine
if your marker lights come on when the switch is pulled out one click they are wired correctly
if they only come on with the headlights then you need to re-visit those

[_Ogre]

Need help on a guage cluster what wires go where on the gang plug

can't help you there, but vetvette has posted many wiring diagrams for 67-72 trucks
they are pretty much all the same

i'm more of a 55-59 truck guy

[Mr.Hyde]

Sorry I'm posting at work on my break and am just trying to get as much said as possible I'll try and clear some of my ramblings up after work when I get a chance and can sit down with the truck and see where I need to start.

[ray_mcavoy]

Originally Posted by Mr.Hyde

The truck is a 1968 c10 283 three on the tree no ac lwb.
.......
Finally I read the neutral safety switch directions and the ones on the wiring diagrams and just can't figure it out.

Being a three on the tree, your truck won't have a neutral safety switch. The factory wiring simply had a wire running directly from the ignition switch "SOL" terminal to the starter solenoid "S" stud. If your new harness has 2 wires meant for a neutral safety switch, simply splicing them together will duplicate that arrangement.

Starting sometime around 1973 I think, GM added clutch safety switches to trucks with manual transmissions. If you want to add one to your truck, it would get connected to the same two wires that would be used for a neutral safety switch on an automatic.

Your three on the tree steering column will have a 2-terminal switch on the top down near the firewall. That switch is only used for the reverse lights.

[Mr.Hyde]

Odd as I'm almost positive it has 4 terminals. I will double check this and get back to you if this is the case makes an easy check mark on my todo list.

As for my questions that I rambled together I will repeat them in a more organized manner.

1.wiring to the dash. The wiring kit has seem to come with wires labeled differently then the wiring diagram states. Example there is one fuel guage wire while the cluster according to the wiring diagram has a guage and a feed. So I am hoping maybe someone can advice me on where this wires run and to which terminal

2.wiper system I assume the wiper labeled wire is power to the switch them is ran to each component?

3. For dome light power would I jump this from red to orange to dome then to back the ground terminal which is the white wire labeled in the picture provided by ogre?

4. Also I notice today on the heater bulb wire (grey) it splits into two running out of the bulb when I assume the clip acts as ground I know one wire goes to the clust where does the second goto?

[ray_mcavoy]

Originally Posted by Mr.Hyde

Odd as I'm almost positive it has 4 terminals. I will double check this and get back to you if this is the case makes an easy check mark on my todo list.

That is odd. This is what the one in my 72 looks like ... it's the switch with the light & dark green wires:

Originally Posted by Mr.Hyde

1.wiring to the dash. The wiring kit has seem to come with wires labeled differently then the wiring diagram states. Example there is one fuel guage wire while the cluster according to the wiring diagram has a guage and a feed. So I am hoping maybe someone can advice me on where this wires run and to which terminal

Yes, the factory wiring had a +12V feed and a sending unit wire going to the fuel gauge. If your new harness only has one wire marked "fuel gauge", that is most likely the sending unit wire. The +12V feed wire might be marked with something like "switched ignition" or similar.

The fuel gauge sending unit wire goes to cavity #4 on the cluster connector (that one is the same for both warning lights or a full gauge cluster).

The +12V feed that's switched via the ignition switch goes to cavity #7 on a warning light cluster. Or to cavity #3 on a gauge cluster. The cavity numbers are marked right on the plastic cluster plug.

Originally Posted by Mr.Hyde

2.wiper system I assume the wiper labeled wire is power to the switch them is ran to each component?

The power wire should go directly to the wiper motor. The switch is connected on the ground side. The wiring that connects the motor to the switch typically isn't included with a universal replacement harness ... you'll have to salvage that from the old harness or run your own wires.

Here is a photo of a typical 67-72 GM truck wiper motor with the terminals labeled:


The power wire from your new harness would go to the "(2) Power" terminal. A short jumper goes from either the "(4) Power" terminal to one of the "Washer" terminals (doesn't matter which one). The remaining terminals are all wired directly back to the switch which is in turn case ground to the dash.

In the low position the switch should ground both the "(1) High" and "(3) Low" terminals.
In the high position, it should only ground the "(1) High" terminal.
And when the switch is pushed for the washer, it should ground the other "Washer" terminal (the one that's not connected to power).

Originally Posted by Mr.Hyde

3. For dome light power would I jump this from red to orange to dome then to back the ground terminal which is the white wire labeled in the picture provided by ogre?

No, don't jump the red to orange.

In the headlight switch pic that Ogre posted, the red 12V input terminal originally received power via an un-fused feed from the battery. Circuit protection is provided via a circuit breaker inside the switch. And there is usually a fusible link in the main power feed wire coming off the battery.

The terminal labeled "orange dome/courtesy" is actually a second 12V feed to the switch. But in many vehicles, it also branches off (ahead of the switch) to feed power to the dome/courtesy lights. This circuit supplies power to the headlight switch for the tail lights and 68+ parking lights. Unlike the red wire, this orange wire is protected by a fuse in the fuse box.

The terminal labeled "white dome/courtesy ground" is a switched ground. When the knob is rotated all the way ccw, this terminal completes the ground for the dome light circuit.

Originally Posted by Mr.Hyde

4. Also I notice today on the heater bulb wire (grey) it splits into two running out of the bulb when I assume the clip acts as ground I know one wire goes to the clust where does the second goto?

Yes, the metal shell of the bulb socket provides the ground.

The original GM wiring had a green wire running from the headlight switch (marked "dk green dash lights") on the diagram Ogre posted to a fuse labeled "inst lps" or something similar. Then from that fuse, a grey wire ran to the heater control light and to the instrument cluster (cavity #12 for warning lights or cavity #8 for a gauge cluster).

[_Ogre]

No, don't jump the red to orange.

i agree with this.
there is an auto reset breaker with the ez wire harness that should be hooked to the headlights only
the factory 68 harness fed the orange wire off the brake light fuse
this means your brake lights, marker lights, dash lights and dome light will all be powered by the brake light fuse
possibly the turn indicators too

all good advise above.
the fuel and temp sending units go to ground; meaning 12v+ to the gauge, then out of the gauge to the sending unit, the sending unit is self grounded

[72ChevyMan1]

I also have the ezwire harness and have a question. Don't mean to thread jump but I'm trying to use my stock gauge cluster plug. But there are wires on the plug that don't match up with the harness. I wanted to attach a photo but it would not allow me to. This is all I'm waiting to run my truck down the road
Thanks guys

[72ChevyMan1]

Here is that plug

[ray_mcavoy]

Originally Posted by 72ChevyMan1

I also have the ezwire harness and have a question. Don't mean to thread jump but I'm trying to use my stock gauge cluster plug. But there are wires on the plug that don't match up with the harness. I wanted to attach a photo but it would not allow me to. This is all I'm waiting to run my truck down the road
Thanks guys

You have the full-gauge "7-hole" style instrument panel, correct? If so, the pin-out of the connector is:

Cavity # / Stock Wire Color / Function
1 / black with white stripe / ammeter (alternator side)
2 / tan with black stripe / brake warning light
3 / pink / +12V switched via ignition
4 / tan / fuel gauge sender
5 / empty
6 / dark green / temp gauge sender
7 / black / ground
8 / gray / cluster illumination
9 / dark blue / right turn indicator
10 / light blue / left turn indicator
11 / light green / high beam indicator
12 / black / ammeter (battery side)

The cavity numbers are molded into the plastic on the sides of the plug.

Most universal wiring harnesses probably won't have the provisions for the stock battery gauge (ammeter) wires that go to cavities #1 and #12. And the harness probably won't have the alternator output and main feed wires configured in such a manner to work with the stock battery gauge either. The easiest way to deal with that would probably be to convert to a voltmeter. Check with member TBone1964 ... he sells 76+ voltmeters that are modified to fit 67-72 gauge clusters.

[Mr.Hyde]

That's the same plug I've been trying to understand. It's fairly confusing and seems like I will be running wire the kit didn't come with. 72chev how did you wire up the ignition switch and the heater? Are you using the 12 circuit?

[72ChevyMan1]

Okay got a majority of them lined out now. I still have a few left out of the loop From the harness of course as well as the plug


On the harness side I am missing wires for tachometer, and fan fan

On the plug side the ports that do not have any connections are 1,2,7,and 12.

[72ChevyMan1]

I wired them up identical to the instructions that were provided with the kit. Only exception is the gauge cluster. There were no diagrams for it. I will go write it down how they say to wire it if it helps?

[Mr.Hyde]

Tachometer is run from the terminal on the distributor. On my harness the color code is purple w/ white lettering

[Mr.Hyde]

I'm more confused about the heater and washer pump as there was no instructions for those. I assume just go by the original harness print.

[ray_mcavoy]

Originally Posted by 72ChevyMan1

On the plug side the ports that do not have any connections are 1,2,7,and 12.

Yes, as I mentioned earlier, universal type wiring harnesses won't have the wires for the stock battery gauge that connect to cavities #1 and #12. You can add these wires yourself (and put inline 4 amp fuses in them) if your charging system wiring is configured similar to the stock setup. Otherwise, converting to a voltmeter will probably be easier.

For cavity #2 (the brake warning light), just run a wire from that terminal out to the switch that's on the proportioning valve or distribution block (typically located just below the master cylinder on 67-72 trucks).

For cavity #7 (ground), just run a ground wire to a ring terminal screwed to some convenient point on the metal dash structure.

[72ChevyMan1]

Ya I won't be using the heater and washer pump and all that

[Mr.Hyde]

Hmm dang wish we could get away with that. We need defrosters and wiper washers. Or do you mean you are using another aftermarket product.

[ray_mcavoy]

Originally Posted by Mr.Hyde

I'm more confused about the heater and washer pump as there was no instructions for those. I assume just go by the original harness print.

Yes, just follow the original harness and/or factory wiring diagram for the heater & washer pump.

The heater blower should have one +12V feed wire (I think the factory color is brown). That wire goes to the switch. Then there are about 3 wires that connect the switch to the resistor network that's used to drop the voltage for the lower speeds. And finally, one wire (usually orange) that goes out to the motor.

The windshield washer pump is mechanically driven off the wiper motor so the only wiring is for the solenoid that engages the drive mechanism. In the pic I posted earlier, there are 2 terminals on the pump that I labeled "Washer". Just connect one of them to +12V that's switched from the ignition and connect the other one back to the wiper switch on the dash (the switch completes the ground to engage the washer solenoid). You might have to do some testing of the washer/wiper switch with an ohmmeter to figure out which terminal is which. Note that the body of the washer/wiper switch is case ground to the metal dash so there is no separate ground terminal.

[Mr.Hyde]

Makes sense. I think that will be what I end up doing this weekend. Since I apparently got my glass in and a few things I knocked off my list. This is actually really helping, again I'll be working on figuring out that gauge cluster plug.