# ‘65 GTO Turn Signal Wiring Diagram



## Roqetman (Aug 31, 2015)

I recently removed the steering wheel to get better access to remove my instrument cluster to replace bad blower fan switch. I have tested all the lights and gauges and everything works as it should except for the turn signals, they worked fine before. I have not yet installed the steering wheel. Does it have to be installed for the turn signals to work? If not, does anyone have a scan of the turn signal wiring diagram they can post? Thanks!


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## O52 (Jan 27, 2019)




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## Roqetman (Aug 31, 2015)

Thank You!


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## tallrandyb (Jun 12, 2021)

Roqetman said:


> Thank You!


@Roqetman , what did you figure out?!? I'm in the same boat, just removed the whole cluster, fixed/replaced lots of stuff, all back together with everything in the dash working correctly BUT now my turn signals (that worked perfectly before) are acting strange. Do I need to have the steering wheel fully re-installed/assembled with cap and everything (stock steering wheel/etc)?

I have power to my flasher can, all four bulbs light fine with parking, right lights flash but no indicator, left lights don't flash, no indicator, and the left rear light just comes on. Seems like I've got a grounding problem?

Thanks!


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## tallrandyb (Jun 12, 2021)

Following up: Found the problem. When I lowered/wedged the steering column down to allow re-installation of the cluster with the new switches installed on the top of it (speaker and power antenna switches that then required a TON of finagling to even get the cluster into the gap), I must have pinched the column wiring harness going to the turn signal switch; I have one wire pinched almost all the way through and two looking rough. Looks like I've got some wiring repairs to do (I am NOT going to try to remove/replace that harness unless it is a last resort).


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## Roqetman (Aug 31, 2015)

Tallrandyb, It’s been a while and I do not remember what I did to fix turn signals. Things to check are the flasher and fuse and the terminals on the fuse block. These old cars will develop corrosion on the fuse block terminals. A good wire brushing with electrical contact cleaner will clean them fairly easily And save a lot of headaches.


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## tallrandyb (Jun 12, 2021)

Roqetman said:


> Tallrandyb, It’s been a while and I do not remember what I did to fix turn signals. Things to check are the flasher and fuse and the terminals on the fuse block. These old cars will develop corrosion on the fuse block terminals. A good wire brushing with electrical contact cleaner will clean them fairly easily And save a lot of headaches.


Thanks, but how could that cause left turn and right turn to act differently from the fuse box?

I’ve repaired and checked continuity on all 7 wires going to the turn signal switch from the crescent connector, and I still have right lights flashing with no dash indicator, and left lights not flashing with the dash indicator holding on (seems it may be dimly lit like it’s “stealing” a bit of ground?).

next I’ll start checking continuity from the dash-side of the crescent connector to everything else, and checking continuity through the turn signal switch circuits in the three positions.


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## tallrandyb (Jun 12, 2021)

tallrandyb said:


> Thanks, but how could that cause left turn and right turn to act differently from the fuse box?
> 
> I’ve repaired and checked continuity on all 7 wires going to the turn signal switch from the crescent connector, and I still have right lights flashing with no dash indicator, and left lights not flashing with the dash indicator holding on (seems it may be dimly lit like it’s “stealing” a bit of ground?).
> 
> next I’ll start checking continuity from the dash-side of the crescent connector to everything else, and checking continuity through the turn signal switch circuits in the three positions.


I pulled the turn signal switch off the column so I can access all the wiring connection points, and disconnected the two crescent connectors from each other so I can test other continuities:

1) when I activate left turn switch, I get continuity from the purple (flasher) wire contact at the crescent (to insure there isn't a break) to both switch contacts for Left front and rear bulbs (yellow and lt blue wires), and when I activate right I have continuity from crescent purple to both right bulbs contacts (dark green and dark blue), on the switch. Purple feeds power through the flasher to the signal switch, so the physical switch mechanism appears to be working, *correct?*

2) Parking and Brake lights work fine in both rears, so I know both rear bulbs filaments and their ground connections are OK, *correct?*

3) Both front parking lights work fine, so I know those parking filaments and the bulb grounds are OK, *correct?*

4) Right front bulb works fine when flashing so I know the right front bright filament is fine, *correct?*

5) Left front bulb is not flashing or holding on when I activate left turn switch; the dash indicator stays ON (maybe weak light), left rear turn filament stays ON, and left front turn filament is OFF. No flasher clicking, but we know it is pulling current (some) through the switch purple wire to send power to the left rear (LED) and left front (incandescent). I pulled the left front bulb and confirmed continuity through both filaments. *Maybe* the left rear LED can power up with minimal current but that's not enough to get the flasher flashing or enough to light up the front left filament?

6) One reminder: Everything worked correctly before doing this dash work, and all four corners of the bulbs/assemblies plus brake light switch and the flasher and their connectors have not been touched.

I thought for a moment that maybe by putting in an LED for the turn indicator that it might not work versus a standard incandescent, but I swapped those bulbs early in my testing and I see the same result with both type bulbs. It is not a dash indicator bulb housing grounding issue because that bulb/housing doesn't ground to the dash (plastic in my rally guage harness), it gets ground from the light blue or dark blue wire when the other is powered,* correct?*

*QUESTIONS:* So *HOW *does the light blue/dark blue wire "provide" a ground to the dash indicator when the opposite wire is powered by the purple? And if it is doing that by "pulling" ground through the bulb filament to the bulb housing ground, then why would it act differently in left turn or right turn mode? Again, right turn flashes fine front and rear (seeming to "pull" sufficient ground to get the flasher going) but with no dash indicator, left turn has left rear on and indicator sitting on fixed but no flash/no click and no left front.

Does this point to the wiring going to the dash indicator bulb? those two (light blue/dark blue) wires split off from the dash-side dark blue/light blue crescent connectors.

So does this mean the ground circuit would have to come from the left/right grounding of the front bulb housings, then through the bright filament of that bulb, then back down under the dash through that light/dark blue wire to the crescent connector, where it then splits off and one wire goes to the indicator bulb and also goes up through the flat wiring pack to the turn signal switch connection where it just ends since its not connected to anything (seems like if it did, then once the dash indicator flashed the opposite turn signal filament would want to flash too since its part of the circuit)?

Or does the turn signal switch ground the "opposite" turn connector inside the switch to the steering column/metal/ground when turning left or right? None of the wires in the loom are grounds.

So could this mean that I'm not getting a good enough ground in the steering column switch/body, maybe because the steering wheel/cap/horn hardware isn't fully installed yet? If so, why would left and right act differently?

Thanks anybody, I'm starting to run out of ideas!


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## RMTZ67 (Mar 12, 2011)

test them coming out of the turn signal switch at the horseshoe. if thy dont work ...you signal switch is bad. switch the good side bulbs with the others.


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