Topic: Ground points for 68

[68 S Code]

Chasing some electrical gremlins in the 68. Figure i would start with grounding of harnesses. So far got the one in the trunk next to the center latch. Under hood cleaned off some paint on the block where the main battery negative cable and alternator wiring get bolted in. Cleaned off paint behind the starter relay and the relays bracket. Cleaned some paint behind the front horns. Getting ready to see if grounding strap from back of RH head to firewall is clean of paint. Its been 5 years since the dash got assembled.

Are there any grounds for the main harness behind the cluster or interior side of the firewall? Have I missed any? The shop manual and even the large format wiring schematics aren't very clear. Thanks in advance.

[Oz390]

There is also at least one more for the instrument cluster to the dash.

[midlife]

Yes: there's a ring connector for the underdash harness to the chassis; eventually, it connects to the ground of the CVR on the back of the dash cluster and provides all of the grounds for the dash lamps.

There's also a ground lug for the front headlight harness. 

[68 S Code]

I had a feeling I remembered one behind the dash cluster which i was hoping to not have to pull the cluster out. But maybe that's why my turn signal bulbs in the cluster don't work. they worked last fall and I know they are new LED bulbs so better work on that.  Underdash harness to chassis. I really need to check that one. Where can i find that one. My dash lights seem to work and then nothing. Also affecting the brake and all turnsignal lights. Car cools down overnight and work but after a few bumps and turns alll shut down.Not sure what was meant by a lug for front lamps? Where is that one? I don't remember it? But no issue with headlights or tail lights working.....so far.

Thanks for chiming in. Oz i see you are back from your stateside trip. Have a fun time?

[midlife]

I had a feeling I remembered one behind the dash cluster which i was hoping to not have to pull the cluster out. But maybe that's why my turn signal bulbs in the cluster don't work. they worked last fall and I know they are new LED bulbs so better work on that.  Underdash harness to chassis. I really need to check that one. Where can i find that one. My dash lights seem to work and then nothing. Also affecting the brake and all turnsignal lights. Car cools down overnight and work but after a few bumps and turns alll shut down.Not sure what was meant by a lug for front lamps? Where is that one? I don't remember it? But no issue with headlights or tail lights working.....so far.

Thanks for chiming in. Oz i see you are back from your stateside trip. Have a fun time?

Many LED bulbs are sensitive to polarity, but on a 67/68, the ground is the shell chasing.  The ground lug for the dash/underdash is located a couple of inches to the right of the dash cluster harness break-out: look for a single black wire near where the turn signal wires break out (orange, blue wires).  Brake and all turn signal lamps don't use this particular ground path; sounds more like a bad turn signal switch. 

The headlight harness ground typically attaches to the radiator support on the passenger side, either on top or just below near the battery area.  Look for another ring connector. 

[68 S Code]

Turn signal switch is an NOS unit purchased a year ago and installed this past summer replacing a Scott Drake repop which was installed two years ago. I'm begining to wonder if its not the 50 year old ignition switch. Looking at the schematics it appears every electrical system seems to run through its contact points. I've been having problems keeping the car running for a year now. In fact just got stranded an hour ago 3/4 mile from the house. Now waiting for it to cool down so I can get her in the garage. Weird part is I made 2/50 mile drives and a couple 25 mile drives since Sunday without a hiccup. Thought my issues were behind me as the motor began breaking in. Got stranded after only 20 minutes driving on Tues and now again today. Thought that maybe higher ambient temps a factor but its in the 50's currently. Just starts missing and then shuts down. Cool down can take as little as 15 min or at times 5 hours. Not that engine is getting hot as it runs between 180 and 195 constantly using a new Autometer gauge. Something affects the ignition. That's why I have been chasing grounds thinking that's my problem. I figure to get these next 2 grounds mentioned and put that possibility to rest. But I fear that may not be the issue.

[midlife]

When the car starts cutting out at engine operating temperatures, the first thing to suspect is the coil.  If not the coil, then some primary ignition system wiring is not making good contact as things heat up.  Clean all of your contacts/connectors and make sure everything is tight.

Some folks jump to the conclusion that it is the pink resistor wire that is giving them fits.  I've found that this wire either works or it doesn't: no intermittent operation.  Rarely does it burn out.

[ruppstang]

I had a starter solenoid that would just shut the engine off. When we checked the voltage at the coil there was 1.5V, tap on the solenoid and the voltage would come up to 9.5V. I replaced it and no more shutting down.

[68 S Code]

Ruppstang thats an interesting point. Although I have never had an issue with starting the car as I was chasing grounds I noticed that the cable leading to the starter from the solenoid had the rubber jacket slightly melted at the big lug on the solenoid. It is an original C7 part so 50 years old. But the the car has never failed to start. It just tends to shut down during driving. Can't count how many times in the last year its stalled. Starts to develop a light miss and then within seconds comes to a stop. Typically takes about 20 minutes of driving to develop. But yesterday it took maybe 5 minutes. Earlier this week 2 drives of 50 miles around town lasting almost 2 hours each without a problem. Usually will re-fire and run for a couple of seconds and then stalls again. Last night we let it cool down for about 2 hours (48 degrees) and re-started with a slight miss. But was able to get her home by blowing through the stop signs. Then once in the garage it just sat there and idled without a problem. The miss is more evident with trans in gear. My son left foot brakes it at intersections and shifts into neutral to keep the rpms up. I think it didn't want to sit out in the cold as its been garaged for the past 30 plus years so it decided to play nice and come home.

Midlife I have already bagged the original restored yellow top coil. I've tried 2 off the shelf coils and now have a MSD Blaster 2 high vibration and high heat coil. I even took it off the intake to make sure there was no excessive engine heat. Its mounted on a bracket where the washer bottle used to be. I don't think its the coil but i dont rule out that the coil is being affected by something else. The what else is the question. Does anyone one sell a replacement ignition switch? Also verified the rear back-up lights and the licence plate light not working. Tail, brake and turn signals at rear were all working. That's been a crap shoot recently.

Another reason Im thinking the ignition switch is that when I turn it to the ON position (1 oclock) nothing works. Once I go into start position and car is running everything works. But in the ON position the radio and turn signals don't work. All interior courtesy lights work when either door is opened as they should when key is out of ignition.

[CharlesTurner]

Many LED bulbs are sensitive to polarity, but on a 67/68, the ground is the shell chasing.  The ground lug for the dash/underdash is located a couple of inches to the right of the dash cluster harness break-out: look for a single black wire near where the turn signal wires break out (orange, blue wires).  Brake and all turn signal lamps don't use this particular ground path; sounds more like a bad turn signal switch. 

Randy, aren't the turn signal sockets hard grounded with an additional wire to the socket?  They have the larger black sockets unlike the metal ones for the dash lights, which do ground to the cluster.

I agree to check the main harness ground behind the cluster.  Also make sure there is a star washer used.  The order on the screw should be wire loop first, then star washer last.  You want the star washer in direct contact with ground surface.  Some folks do this wrong and put it on the other side.

Also, it is very uncommon for owners/shops to miss installing the star washers at all the ground points at the engine and engine bay.  The rear engine ground to firewall should have one at both ends, the headlight harness will be grounded in a couple spots with them and the negative battery terminal to block connection will have star washer too.

[midlife]

Randy, aren't the turn signal sockets hard grounded with an additional wire to the socket?  They have the larger black sockets unlike the metal ones for the dash lights, which do ground to the cluster.

On 67/68's, the only two wire bulbs are alternator lamps, oil pressure indicator lamps, and brake lamps.

[midlife]

Midlife: Also verified the rear back-up lights and the licence plate light not working. Tail, brake and turn signals at rear were all working. That's been a crap shoot recently.  Back up lamps and running lamps (license plate) are on completely different circuits.  The only thing in common are the grounds.

Another reason Im thinking the ignition switch is that when I turn it to the ON position (1 oclock) nothing works. Once I go into start position and car is running everything works. But in the ON position the radio and turn signals don't work. All interior courtesy lights work when either door is opened as they should when key is out of ignition.  Turn signals should work in ACC as well as ON; same for radios.  Turn signal flasher can and radio (and backup lights) are all on same circuit, so fuse  or fuse box clips (upper left horizontal) are indicated. 

[68 S Code]

Caspian i did install the star washer to block from negative cable. But no where else. Looks like I will be re-doing some things. Yes there is a blade connector at each tail light bulb socket so I assume for a ground wire.

[68 S Code]

Well I swapped out the ignition switch with an aftermarket unit after reading a Mustang monthly article on how to remove the key cylinder. I did the same with the starter solenoid simply for piece of mind. Took her out for a drive and only made 40 minutes and maybe 15 miles in the neighborhood before stalling out. First time I lucked out where it stalled as I turned on my driveway. Didn't have to call home to be picked up by one of my kids. She re-fired and my son took his multimeter to the coil. Voltage varied from 1.4, 2.3, 3 and 4V before she died again. My son thinks the resistor in the ignition wire is possibly heating up and causing the voltage drop problem. He said it might be possible to cut it out and splice in a modern resistor. Has anyone tried to replace the original resistor in the factory harness. Did you have good results? It would seem to make sense that it is the resistor because once the car cools down meaning possibly the resistor cools down she re-fires. Sometimes cools down enough to re-fire but a weak signal means she is limping home with a misfire. Or is my resistor heating up possibly due to the main harness ground which i still haven't tackled? I may pull the cluster on this rainy Sunday to have a look around. By the way all the turn signals and brake lights only worked for the first 10 minutes of the drive. Then those features went dark. Even with the new ignition switch.

[1967 eight barrel]

Questions:
1. Does the vehicle have points?
2. Factory Tach?