# 1968 GTO/Lemans Dash Circuit Board



## PontiacJim (Dec 29, 2012)

I drew up a schematic of the 1968 GTO/Lemans/Tempest circuit board using an actual repop circuit board. These are said to fit 1968-1972, but cannot confirm that as sometimes there are changes within the years. This is for my '68 Lemans. It is the non-rally gauge circuit board having the idiot lights.

I wanted to show both the Ground (G) and Power (+) sides of the lighting used to illuminate the dash and the idiot lights. I also show the various Grounds Screws that secure the circuit board to the metal dash pod. My car has the Speed Warning Speedometer and uses a brass contact pin seen in the upper right, otherwise that hole will be blank. My fuel gauge also has the low warning light as part of the Speed Warning option, so my hook-ups may look a little different from the standard fuel gauge. Red/Green are ground wires while the Black wire is a power/stud to the gauge. There is 1 small hole above the Oil Light socket which I do not know what it is for.

The wiring harness dash plug gets fitted into the Harness Plug position, and has copper "fingers" that make contact with the corresponding Harness Plug connections, 5 on top & 6 on bottom. I included a contact diagram in the lower left outlining what each "finger" powers on the circuit board. NOTE: Do Not apply 12-Volt power to the ground fingers in an attempt to diagnose/trouble shoot a bad electrical connection. You WILL melt/damage the circuit board copper circuitry as both the circuit board plastic and copper circuitry are very thin and if shorted out, ie applying power at the ground "fingers," will produce the smell of melting plastic and heat where it has melted. This will require that you spend another $100.00 plus shipping to replace the melted circuit board - just sayin' 

Also included a pic of the back of my dash/cluster pod so you can see how it lays on the back and the light sockets are positioned.


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## pontrc (Mar 18, 2020)

Thanks PJ that is one of the things on my bucket list 👍


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## deanhickey (Apr 6, 2015)

another great resource Jim, Thank you for sharing.


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## etennett (Aug 15, 2020)

PontiacJim said:


> I drew up a schematic of the 1968 GTO/Lemans/Tempest circuit board using an actual repop circuit board. These are said to fit 1968-1972, but cannot confirm that as sometimes there are changes within the years. This is for my '68 Lemans. It is the non-rally gauge circuit board having the idiot lights.
> 
> I wanted to show both the Ground (G) and Power (+) sides of the lighting used to illuminate the dash and the idiot lights. I also show the various Grounds Screws that secure the circuit board to the metal dash pod. My car has the Speed Warning Speedometer and uses a brass contact pin seen in the upper right, otherwise that hole will be blank. My fuel gauge also has the low warning light as part of the Speed Warning option, so my hook-ups may look a little different from the standard fuel gauge. Red/Green are ground wires while the Black wire is a power/stud to the gauge. There is 1 small hole above the Oil Light socket which I do not know what it is for.
> 
> ...





deanhickey said:


> another great resource Jim, Thank you for sharing.





PontiacJim said:


> I drew up a schematic of the 1968 GTO/Lemans/Tempest circuit board using an actual repop circuit board. These are said to fit 1968-1972, but cannot confirm that as sometimes there are changes within the years. This is for my '68 Lemans. It is the non-rally gauge circuit board having the idiot lights.
> 
> I wanted to show both the Ground (G) and Power (+) sides of the lighting used to illuminate the dash and the idiot lights. I also show the various Grounds Screws that secure the circuit board to the metal dash pod. My car has the Speed Warning Speedometer and uses a brass contact pin seen in the upper right, otherwise that hole will be blank. My fuel gauge also has the low warning light as part of the Speed Warning option, so my hook-ups may look a little different from the standard fuel gauge. Red/Green are ground wires while the Black wire is a power/stud to the gauge. There is 1 small hole above the Oil Light socket which I do not know what it is for.
> 
> ...


Jim where does the light that powers the ash tray light plug into? Mine fell and I can’t tell where it fell from


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## PontiacJim (Dec 29, 2012)

etennett said:


> Jim where does the light that powers the ash tray light plug into? Mine fell and I can’t tell where it fell from


Read this post, it may answer your question.









Ashtray light wiring conundrum 68 gto


Anyone know how this hooks up? Is a clip broken off end of light possibly? All this wiring is factory. Does this light gain power from dash circuit? I do have one open spot left in dash circuit and the wire clearly grounds on bottom of ashtray base.




www.gtoforum.com


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## etennett (Aug 15, 2020)

PontiacJim said:


> Read this post, it may answer your question.
> 
> 
> 
> ...


Perfect! Thanks


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## O52 (Jan 27, 2019)

Here you go...


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## etennett (Aug 15, 2020)

O52 said:


> Here you go...
> 
> View attachment 144292
> 
> ...


Perfect thank you


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## 68 DropTop (Jan 4, 2022)

Hello gents,

New today and already used Pontiac Jim's handy diagram the other day. Thank you for posting though I did find an error on it.

The notations of the wiring connector lists a "Ground" between the "Dash Lights" and the "Temp Light". In my experience that is incorrect. That is NOT a ground. That is the fuel sender wire. If you cut it, all your dash lights will still work but your fuel gauge will stop reading.

Since I would feel bad if this was all I said, here are my notes on removing the dash...

*68 LeMans Dash Removal*

Disconnect battery (optional)

Remove (2) screw from underside top of cluster holding dash pad
Pull dash pad from top to pop free
Unplug wires from floor light (white toward driver, orange toward passenger)

Remove power antenna switch & power convertible top switch, set aside bridging clip brackets so you don’t lose them.
Remove screw above speedometer holding cluster
Remove stereo - remove faceplate – use stereo “keys” on each side to free stereo from bracket.
Remove stereo bracket.

My lower panel with the vent ducts is already removed, so I’m not covering that.

Dash plate has 2 or 3 screws built in to it that point toward the engine, usually with 3/8 cap style nuts, one under the left side instrument or combo (fuel, etc), one under the right gauge or clock, and something to the right of the stereo. In my case it’s kind of a stud that I added a small Phillips screw w/ washer. Remove what is there. A 3/8 socket with an 8 inch extension should work.

The dash is now free…..but you gotta drop the steering wheel

Remove the plate below the steering wheel.
Remove (2) 9/16 nuts and (1) 9/16 bolt with a socket wrench. Hold up the steering wheel before you remove the last nut. The bolt will have a wedge shaped spacer will fall at some point. Put it back when you reassemble.
Disconnect speedometer cable.

The light switch and heater controls are set below the frame so you will need to tilt the dash from the top and roll it toward you. There is a wire harness attached to the top of the instrument cluster.

This is as far as I needed to get this time. I'm sure there is more to it.


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## PontiacJim (Dec 29, 2012)

68 DropTop said:


> Hello gents,
> 
> New today and already used Pontiac Jim's handy diagram the other day. Thank you for posting though I did find an error on it.
> 
> ...



Thanks for that catch and your guide, I just edited the diagram. I have another diagram posted of the circuit board and how the copper cicuits are routed - this should be of help. This circuit board diagram is for the standard "idiot" light gauges, not the rally gauge option - as this is what my Lemans has. 

Mine has the fuel gauge with the Low Fuel Warning Light - which I included a photo of the back/wiring side. Don't let the photo confuse. The circuit board lays over the green/red wire studs - looks like I replaced them on top of the circuit board in my photo, oops. Looking at it again, the left of the Fuel Gauge is the signal wire that would come from the gas tank sending unit - the light green wire attached to that stud. The black wire in the middle is a ground specific to the Low Fuel Warning gauge, and the wire to the right is also a Ground (G) and is a red wire in my photo.

I think this should correct my diagram, but if you see something I missed, post it, and I can alter the diagram.


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