# '67 GTO Electrical Gremlins



## Andrew69 (Dec 28, 2017)

Okay, working on this '67 GTO and it is being uncooperative.

400 CI with TH400 transmission. AC, power windows, ram air, convertible top.

Symptoms:

The radio works intermitted as does the climate control fan.

The interior light, under the dash, directly above the console will sometimes come on with the rest of the interior lights, sometimes not come on and sometimes comes on with the door closed and interior lights off.

I spot a ground cable from the RH inner fender to the frame. One is from the LH rear valve cover to the firewall. One from the firewall to the coil bracket is missing. The negative battery cable has the heavy gauge wire routed to the engine, but has a ~ 12g wire running over the fender well but not connected to anything. The tip end is bare and looks like it might have once had a connector crimped to it. Where should it connect?

There are two black ground wires in the under dash wiring harness secured to the steering column support bracketry. The tail light wiring is newly replaced and all seems to be okay back there.

I noted today the alternator is sparking at the rear terminal. I found the threaded stud where the wires attach is lose, and it twists as I try to remove the nut securing the wires. It will need to come off to be repaired/replaced. Any suggestions here? Might this affect the radio and interior fan?

I suspect my lighting and radio problems may be grounding related. If I install a new set of three ground wires might I see an improvement? Where should the secondary wire on the negative battery cable attach?

I know this is a lot. What do you think?


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## cij911 (Oct 25, 2017)

Andrew69 said:


> Okay, working on this '67 GTO and it is being uncooperative.
> 
> 400 CI with TH400 transmission. AC, power windows, ram air, convertible top.
> 
> ...


OK a lot here, so let's start with the basics - do the radio and climate fan share a common power source or ground ? If so, check those with a volt meter and confirm good power and ground - wiggle the radio and move the fan switch while checking.

You should have the battery grounded to the engine. You could also ground the battery to the chassis as well.

You should check the ground location on the steering column support bracket - I suspect that could be a problem and would run those to a good chassis ground. You'll be able to test easily with a voltmeter.

Good luck


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## Andrew69 (Dec 28, 2017)

I'll run that secondary negative battery wire to a suitable body connection ground. I'll reroute the dash grounds to dashboard metal and check that the fuses are making a good connection in their respective mounts.

The alternator sparks at the rear connection because it is not longer secured to the body of the casing; apparently due to rust. Is this repairable or does it call for a replacement alternator?


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## cij911 (Oct 25, 2017)

Andrew69 said:


> The alternator sparks at the rear connection because it is not longer secured to the body of the casing; apparently due to rust. Is this repairable or does it call for a replacement alternator?


I'm not sure which connection you are referring to "sparking", but the large post is the main output of the alternator which powers your main power block / terminal. The other two lines essentially tell the voltage regulator (external) what is happening with your alternator output. If there is a "spark" or arc coming from the the main output wire to the alternator chassis, then I would suspect you have an exposed or bad wire. Check the resistance or just replace the wire with a nice thick gauge 8 - 10.....


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## Andrew69 (Dec 28, 2017)

The back of the alternator has a stud on which the hot wires attach. This stud has a red insulator. The stud has rusted and loosened and was rattling around arching off the alternator body.

I removed and opened the alternator. Found the brushes well worn so ordered a newly rebuilt alternator stamped 1100700. 

Also ordered a new set of ground straps plus cleaned all grounds that I can find and added star washers.

Now one of the hot wires, black and orange striped, that connects to the alternator has an inline fuse. I checked the fuse and found it empty. So what does this line do and how did the car run with no fuse? Will I burn down the car if I put a 30 amp fuse in there?

Thanks all.


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## cij911 (Oct 25, 2017)

Andrew69 said:


> The back of the alternator has a stud on which the hot wires attach. This stud has a red insulator. The stud has rusted and loosened and was rattling around arching off the alternator body.
> 
> I removed and opened the alternator. Found the brushes well worn so ordered a newly rebuilt alternator stamped 1100700.
> 
> ...


If there was no fuse, then there was no current on the wire.

You should trace the wire and see where it leads....


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## Andrew69 (Dec 28, 2017)

cij911 said:


> If there was no fuse, then there was no current on the wire.
> 
> You should trace the wire and see where it leads....


True the lack of power transmission through the wire. The wire disappears into a well taped wiring harness bundle with no obvious exit point. I would rather not unwrap it and hope someone here is familiar with it.


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## JNYBOY (Sep 28, 2017)

That inline fuse is the supply for the dash lites....had that problem a while ago...Good Luck !! AGC 30..


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## Andrew69 (Dec 28, 2017)

JNYBOY said:


> That inline fuse is the supply for the dash lites....had that problem a while ago...Good Luck !! AGC 30..



Thank you!


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## Andrew69 (Dec 28, 2017)

For the benefit of anyone out there facing the same problems:

I installed a newly rebuilt correctly stamped alternator
Inserted a 30 amp fuse into the inline fuse holder right behind the alternator
Located a fuse in the panel that was 10 amp that should have been 20 amp
This was the reason for the radio sometimes not working, the 10 amp would blow
Installed new ground straps from the engine to firewall and frame to inner fender
Have not yet installed ground from coil bracket to firewall because I just cannot reach it
Put star washers under every ground connection I could find. Most looked like they might not be making connection

Everything of concern discussed above seems to be working now.

However I checked the dash lights at night and while they are illuminated they are rather dim. Might they have the wrong bulbs? Which bulbs are recommended?

Thanks for the help guys.


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## 64GTOConvertible (Aug 28, 2016)

Do you know how to turn the knob to adjust the light brightness? I am surprised how often that comes up...


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## PontiacJim (Dec 29, 2012)

"However I checked the dash lights at night and while they are illuminated they are rather dim. Might they have the wrong bulbs? Which bulbs are recommended?"

Does turning the Light knob change the brightness or dim it further? The dash lights should have a low level dimness and a high level brightness if it is working correctly. Could be a bad rheostat on the light switch as these do fail/go bad over time. 

My experience with my '68 is that the dash lights were not as bright as I would like either, and probably not as bright as we have become accustomed to in our newer vehicles. It has been pointed out before that I believe using a replacement LED bulb will give you a brighter light as well. I will probably do this with mine when the time comes. :thumbsup:


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## Andrew69 (Dec 28, 2017)

Turning the light knob does dim it further to darkness but won't get bright enough. That's a good question. 

A rheostat replacement would be the easiest thing to do, if that will solve it. There might be a couple of wires I could jump to test a direct connection. Since I already replaced the air conditioning ducts I really don't want to have to change out the bulbs.


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## Andrew69 (Dec 28, 2017)

Well the dash lights remain kinda dim but they do light.

Today I thought I had everything wrapped up including 134A in the AC system. Took the car for a drive and the interior lights came on and wouldn't turn off. I could depress the door jamb switches and they will slightly dim but won't turn off.

If you turn on the headlights the "Battery" idiot light illuminates. Probably from using too much current.

I pulled each fuse, one at a time, and they never turned off. Even when I remove the key from the ignition. :crying: I twisted the light switch back and forth multiple times.

Every ground I could find has a star washer under it.

Do you think I need to replace the light switch and maybe the door jamb push buttons? Does the light switch have a ground wire too? I thought I had rid this car of the electrical gremlins.


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## Andrew69 (Dec 28, 2017)

This tells me it might very well be the light switch. http://www.gtoforum.com/f50/interior-lights-permanently-67-gto-111841/ 
I'm going to replace it plus the two door jamb switches. What's the trick to removing the light switch?


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## Sixty7GTO (May 4, 2017)

Hi Andrew,
Where did you order the alternator from and do they also do date codes?


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## Andrew69 (Dec 28, 2017)

I bought the alternator through eBay from Buckeye Auto Electric. While the one purchased is stamp correct for the car it was not date code correct. You could contact them to learn your options.

Home - Buckeye 

Good luck!


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## Andrew69 (Dec 28, 2017)

Well a new headlight switch and door jamb switches did not solve the problem. The interior lights will not turn off unless I remove a battery cable. I pulled each fuse, one at a time and they will not turn off. I've traced the wires under the dash hoping to in-pinched wire without success. I'm now thinking the light at the rear of the console might be the culprit. I'll check it tomorrow.

Maybe I need a priest for an exorcism. Any ideas?

:crying:


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## Andrew69 (Dec 28, 2017)

Hold it! Cancel the priest and exorcism! This gremlin is slayed, or at least beat back temporarily.

The socket with bulb at the rear of the console had wiggled out, with the metal socket contacting the metal housing providing a path to ground. Popped it back in and the interior lighting is back to normal.

Maybe this will help someone else facing the same dilemma.


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