Dash cluster ground
 

The wiring diagram for’65 GTO shows “Instrument panel ground on brake pedal bracket” Can anybody provide more details? Is there a ground wire that runs from the cluster to the brake pedal bracket? Exactly how / where does this wire attach to the cluster? Exactly how/where does the wire attach to the brake pedal bracket?

If you look at the 65 wiring diagram it shows the High beam indicator having 2 ground wire points. 1 going to the brake
pedal bracket, other on the printed circuit. If I remember correctly the ground wire goes to the right side of brake pedal bracket
should be a black wire with an eyelet on it.

I have a 64 dash harness at home and will check the high beam socket to see if it has an xtra wire on it. Other light sockets at dash only have one wire, the socket grounds to the printed circuit which grounds thru the wire coming off the high beam indicator socket.

Dash cluster ground
 

I’m a little confused. ‘65 doesn’t have a printed circuit on back of instrument cluster.

Dash cluster ground
 

Oh, wait. I sent the reply above before looking at the wiring diagram again. Now that I’ve done that, I see exactly what you were explaining. Never mind the printed circuit issue. I see that I need to check out what is going on with the black wire coming from the high beam indicator. Don’t know how I missed that when studying the diagram earlier. Thanks very much for this tip. Will try to contort myself up under the dash today to see what is going on with this.

Dash cluster ground
 

Evidently the high beam lamp socket was not fully seated in the back of the cluster. Unplugged it and then snapped it back in place firmly and everything worked like it should i.e dash lights come on when headlight switch is pulled out and gas gauge reads normally instead of falling to Empty. Thanks for your help on this weird issue.

Glad you got it fixed. Your right on the printed circuit, the back of the cluster is metal if I remember correctly.
I put another ground wire on mine when I put it back together, goes from a mounting stud or something like that to another metal part
similar to brake pedal Bracket. Was 12 years ago so memory could be a little sketchy, LOL.

1964 and 65 GTO Dash cluster ground
 

The factory ground for 64 and 65 Pontiac A body cars was a single black wire. At one end (white arrow) that wire is attached (uncovered) to a flat plug-in tab which was made onto the side as part of the silver-metal bulb socket with the lime green wire in it. (That lime green wire gets 12 volts of + battery power when you turn your high-beam headlamps on.)

The black wire then goes into the tape wrapping only to re-appear underneath the dash above the brake pedal support. The other end of that black wire is a crimped "ring terminal" end. The ring is secured to the side of the unpainted support structure which is part of the under-dash reinforcement for the pedal(s) and the master cylinder. There was a small star washer in-between the ring end and the brake pedal support.

Dash cluster ground
 

Yes, I noticed the unique configuration of the high beam socket with the black ground wire attached once I got a good view of the back of the instrument cluster. The free end of this ground was firmly attached to the brake/clutch pedal bracket so that didn’t appear to be an issue. The high beam socket seemed to be firmly seated also. It took a pretty good tug to remove it. I had repainted the outside and inside of the metal cluster housing, so maybe there was just enough paint around the hole to prevent a good ground. Funny that it worked fine for 9 years though. Go figure.