72 GT wiring question

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72 GT wiring question

Postby GT72 » Tue Jun 20, 2017 8:29 pm

I have a wiring issue I am trying to solve. I never met the prior owner so I am not sure what he was doing. But under the dash he had a push button, one pole was empty and the other pole had a black wire and a black and looks like double purple wired together. I tried tracing these 2 wires out but after unwrapping the bundle about half way I decided maybe I should stop. Any idea what these 2 wires could be for? I also could not find them on a wiring diagram. they are in the bundle under the dash to the right side of the steering column. And no it is not close to turning the key on
Thanks
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Re: 72 GT wiring question

Postby KZVEGA » Tue Jun 20, 2017 10:06 pm

If I remember correctly they are for neutral safety/clutch safety switch.
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Re: 72 GT wiring question

Postby spencerforhire » Wed Jun 21, 2017 6:27 am

Sounds like the previous owner did not understand the neutral/clutch switch, and just wired a push button instead. I would guess that the black wire you see goes directly to the battery and the button needs to be pushed to start. The two purple wires normallyplug onto the clutch switch on a manual trans car and the shifter of an automatic one. If you have an automatic, you need to hook it up properly so the car will only start in neutral and park. With a stick, a clutch lockout switch is a good idea, but not a deal breaker.
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Re: 72 GT wiring question

Postby GT72 » Wed Jun 21, 2017 4:34 pm

Sorry guys, maybe I was a little too vague. It is one small gauge black wire and one small gauge black wire with purple stripes. That's what I called double purple stripes. Sorry
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Re: 72 GT wiring question

Postby spencerforhire » Thu Jun 22, 2017 6:34 am

There was a pair of wires, black and black with blue & pink stripes wire that supplied power to the idle stop solenoid, and are shown on the diagram sharing a 4-pin plug with the pair of large purple wires for the clutch switch. A pic might help.
The "fleet"-
77 Vega Estate wagon- project(someday)will have TPI305/T-5, S-10 spindles/axles
72 Vega HB Drag Car -383/'Glide/9"(9.35@146.19)(5.94@117.28 1/8th)
76 Vega GT- 400/4spd/9" retired from active duty(rusty)
03 Silverado 2WD ex.cab (work truck/parts hauler)
04 Silverado 2WD ex.cab (retired)
06 Haulin' 20ft enclosed car transporter
93 Suburban- 350/4L60(retired)
00 Saturn SW2- wife's car
01 Saturn SC2- younger son's project
00 Saturn SL2- daughter's car
98 Saturn SW2- spare
and 3 more Saturn "parts cars"
Note- the very act of listing all of these has made me realize I have some kind of problem.....

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Re: 72 GT wiring question

Postby GT72 » Thu Jun 22, 2017 1:37 pm

Okay, I went back and looked, found the plug with 2 large gauge purple wires and the nubs of the 2 wires he cut off and spliced together at the push button. Now this was a manual tranny and I am going with an automatic. How should I proceed with these wires? They are a small gauge black one and a small gauge black with 2 purple or pink lines on it
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Re: 72 GT wiring question

Postby GT72 » Sun Jun 25, 2017 9:08 am

So after asking everyone I know and even people that I don't, haha, it seems the 2 purples should be run to my neutral safety switch on my shifter?
Question still remains, what are the 2 small gauge black and black with purple or pink stripe wires and what should I do with them?
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Re: 72 GT wiring question

Postby monzaaddict » Thu Jul 06, 2017 4:31 pm

on a 4 speed the clutch (neutral safety) switch is on the clutch pedal.

You need the mounting stalk. This is for a camaro but I think it is the same for a vega/monza.
http://dev.johnsclassiccars.com/parts/d ... amaro/9811

You need this switch for your vega.
http://www.ebay.com/itm/VEGA-MONZA-1971 ... 6S&vxp=mtr

I think it works like this

purple wires connect when pedal is depressed ( starter/ignition switch circuit is engaged allowing car to start)

black wires disconnect when pedal is depressed (idle solenoid is disengaged I assume to prevent engine speed flairing when disengaging transmission).

idle stop solenoid acts as an idle screw would setting idle speed when running and when ignition is off allows carb butterflys to fully close preventing run on.

Do you have the idle stop on the car still? If not you could just eliminate the switch entirely and connect the purple to purple. just don't forget to take transmission out of gear when starting so you don't drive through your garage door, run over your kid or pet.

hopefully someone else will chime in.
Last edited by monzaaddict on Thu Jul 06, 2017 5:42 pm, edited 3 times in total.
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Re: 72 GT wiring question

Postby monzaaddict » Thu Jul 06, 2017 5:09 pm

I found this article that discusses the idle stop solenoid on a 73 4 speed car. It says the solenoid is used to prevent dieseling when hot engine is shut off.

scroll down to title hatching trouble

https://books.google.com/books?id=idQDA ... ga&f=false


Here is another article by smokey yunick confirming the idle stop solenoid is to prevent dieseling.

https://books.google.com/books?id=Gr9KV ... ga&f=false
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Re: 72 GT wiring question

Postby GT72 » Thu Jul 06, 2017 8:48 pm

I am going with an turbo 350 automatic and a 350.
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Re: 72 GT wiring question

Postby monzaaddict » Thu Jul 06, 2017 10:37 pm

The purple wires definitely go to the park neutral switch on the shifter.

I am guessing the wires for the idle solenoid get connected to each other ( or disconnected since you are not likely using the idle stop solenoid.

The reverse light switch with a a 4 speed is on the transmission. The wires will have to be run to the switch on the shifter with an automatic transmission

I know that there have been instances where the micro switch on aftermarket shifters would burn out from the current that would go through them. It probably will not be a problem - just something to remember if you have to trouble shoot a no start issue.
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