# `68 under dash wiring



## Rukee (Feb 8, 2007)

Just about to replace the under dash and engine wiring harnesses on a `68 GTO, non A/C car. Any tips or cautions?


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## jmt455 (Mar 26, 2012)

Are you removing the cluster and heater control or trying to do this while they are installed?

If you're removing them, here are a couple of suggestions:
-Make sure you drop the steering column before trying to remove the gauge bezel.
-Be very careful with the heater control; it's easy to crack the lens. 
-I think it's easiest if you remove the 3 heater control cables from the heater box before trying to remove the heater control.
-It's a PITA to get the harness back into the black plastic retainer above the gauge cluster, but be patient and make sure it's tucked up there where it belongs.
-I added some grounding wires from the studs and metal ground straps in the cluster to a ground terminal strip that I mounted up behind the glove box. I ran the terminal strip connector to a redundant ground on the IP structure; I have never trusted those metal ground straps to maintain good connection to the dash metal.
-I also added a 12V power port inside the console bin; it's handy for cell phone charging and Garmin power.


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## Rukee (Feb 8, 2007)

I'd rather leave that stuff in if possible. Is it possible?


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## 68GTO4004Spd (Jun 19, 2008)

Be prepared to have you hands cut to ribbons lol. Do yourself a favor and take the front seats out, at least the drivers side, unless you are a contorsionist. Take pics and label things before you take it apart, I wish I was smart enough to do that, would have made it much easier. I still have some things that aren't hooked up right, but it runs and drives so f it, it's on my long "one of these days" list. I didn't know you had a 68 and the 65.


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## Rukee (Feb 8, 2007)

It's not my car, just helping a buddy out by installing it for him. For a fee of course.


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## 68GTO4004Spd (Jun 19, 2008)

Ha, you would have to pay me a crap load to do that again, I hate working under the dash.


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## gjones (Oct 8, 2012)

*cable bracket*

Also, be really careful when taking the cable connectors off. That plastic is very brittle. My heat/defog cable mount was busted when I got it, and seemed kind of crunchy. Was able to epoxy it back together till I got a new one. So far so good.


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## Rukee (Feb 8, 2007)

Thanks for the tips guys!! :cheers
Tackled the under hood harness today which was a challenge because they had changed the location of the coil, rerouted the starter wires because of headers, removed the temp sensor and have the wrong alt and I didn't want to mod the harness at all, going under the dash tomorrow. Taking the new harness out of the bag, glad to see the gauge cluster connects with a single plug and not all separate! But yea, seems to be a lot of connecters.


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## Rukee (Feb 8, 2007)

Something I found odd, a green wire exiting the harness with the alt plugs and temp sensor, (I thought it might be for a A/C throttle/idle step up solenoid) they had plugged into with a jumper wire to key'd 12v+. Any idea what the green wire is for and why they would have been jumping it with a key'd input?


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## Rukee (Feb 8, 2007)

Looks like the under dash harness goes over the top of the gauge cluster, is there an easy way to pull the gauges? Looks like maybe the radio and temp controls need to come out at the same time?


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## bondobill (Oct 24, 2011)

Rukee said:


> Looks like the under dash harness goes over the top of the gauge cluster, is there an easy way to pull the gauges? Looks like maybe the radio and temp controls need to come out at the same time?


To answer your questions
Nope, and Yep 
We didn't replace the dash harness in Brents 68 but we did have it out to repair a few items. 
You can try working around all that crap under there but the job might go easier taking out the gauges, radio, heater controls ect.
I was lucky tho, I had a patient, agile 23 year old with good set of eyes under the dash doing the dirty work.
Every time I got under there it would take me 5 minutes to crawl back out.


Bill


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## Rukee (Feb 8, 2007)

Yeah, I hear ya!! I pulled it out with the help of this thread...
http://www.gtoforum.com/f50/68-dash-removal-30599/
Only because I was pulling the whole harness I was able to leave the headlight wiper and ignition switches in. Even so, what a spaghetti nightmare!!


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## 68GTO4004Spd (Jun 19, 2008)

Try putting it back in 2 months after you took it apart and you didn't take pics or label anything. Nothing but nonstop fun. 
How many tools have you dropped on your forehead so far?


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## gjones (Oct 8, 2012)

*The mad dash*

Oh, it's not that bad. By the third time pulling it, you'll be able to do it blindfolded!  When I pulled mine out for the third time, (for speedometer/odometer problems, the last time), t'was but a snap. Didn't even have to label anything!


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## Rukee (Feb 8, 2007)

Okay got 98% done and the left blinker light comes on with the dash lights, dims with the dash lights, and blinks with the blinker but not as bright as the right, wtf?


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## joedee (Dec 13, 2012)

Rukee said:


> Okay got 98% done and the left blinker light comes on with the dash lights, dims with the dash lights, and blinks with the blinker but not as bright as the right, wtf?


I would check the plug in the back of the gauge pod to make sure the connectors on the printed circuit board are not touching where it plugs in.

Joe


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## Rukee (Feb 8, 2007)

Good point, so I pulled it back out and there is no way for the connections to get crossed. But checking voltages at the back of the cluster I found it had a weak ground. I connected a wire from a good ground to the back of the cluster attaching to a ground screw close to that bulb and voilà! It works right. 
But that has me thinking, what else am I grounding? And now through the printed tape back to the plug in. Anyone know where the cluster ground come from? I really don't want to mod this brand new harness and tie in a ground to that wire.


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## gjones (Oct 8, 2012)

*Ground tracking*

I almost posted about the dash ground, but was reluctant for the fact of repeating, ad nauseam, the virtues of a good ground. On the '66, there is a stabilizer bar that attaches at the rear of the cluster to a point on top of the steering column, creating an excellent ground. Not sure if the '68 has it or not. I noticed strange goings on at the gauges when I forgot to connect that deal. Hopin' you got it all o.k.!


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## jmt455 (Mar 26, 2012)

Cluster grounds through those little metal straps to the cluster attachments.
Make sure you have tightened the nuts that attached the cluster to the dash metal on the back side.

That ground set-up is the reason I mentioned adding the redundant ground wires in my previous post.


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## Rukee (Feb 8, 2007)

Strange though, following the tape the dash light and the left blinker light next to it are grounded through a gray wire coming from the plug in at the back of the cluster.


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