ConcoursMustang Forums
Restoring - General discussions that span across many different groups of years and models => Misc Items => Topic started by: 68 S Code on October 12, 2016, 07:22:31 PM
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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.
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There is also at least one more for the instrument cluster to the dash.
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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.
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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?
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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Questions:
1. Does the vehicle have points?
2. Factory Tach?
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I would run a temporary wire from the hot side of the solenoid to the coil and go for a drive and see what happens. You will have to remove it to stop the engine.
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I had to do a bit of wiring for the Pertronix II so I didn't lose the tach feed and had a constant 12V hot. I was wondering if he had a Pertronix. If the tach fails or is intermittent in operation it cuts the feed to the coil as well.
-Keith
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No factory Tach but i am unsure of the underdash wiring harness as i did install a tilt column from a 68 GT Fastback i once had back in the late 80's. i remember grabbing all the tilt components and don't remember if it was a sub harness or the entire dash harness. That car did have a tach and AC which my vert did not.
Yes still running points. That was going to be a future question though. Distributor is going back to Tim O'Connor in the next two weeks because something not right with mechanical and vacuum advance numbers. How have people faired with the Petronix upgrade?
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It could possibly be connected to the tilt. The ignition circuit runs through the tilt wiring so when the wheel is tilted it will not start. The test I suggested above will by pass all of that.
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No factory Tach but i am unsure of the underdash wiring harness as i did install a tilt column from a 68 GT Fastback i once had back in the late 80's. i remember grabbing all the tilt components and don't remember if it was a sub harness or the entire dash harness. That car did have a tach and AC which my vert did not.
Yes still running points. That was going to be a future question though. Distributor is going back to Tim O'Connor in the next two weeks because something not right with mechanical and vacuum advance numbers. How have people faired with the Petronix upgrade?
good luck with tim. his website says closed until further notice. been that way for several months now.
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I'm already in line with a dual vacuum advance unit for a while now. He told me to send it in but i was hoping to add another 250 miles to break the motor in before winter and the distributor pull.
Well I pulled the cluster. i can see the tiny screw at the ring from small gauge black wire being grounded to the LH steel vertical brace. Just picked up some star washers so will get that one. The ring is clean as is the paint off the brace. But I'll give it a go.
Don't really know where to look for that other grounding ring for the main harness though. Lots of harness in the way. Hints or picture would be great.
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Regarding the jumper wire that could be an issue. The wire from ignition switch to coil is actually only supposed to be 6 volts due to an inline resistor. Trying to feed the coil with 12v directly probably not a good idea. However when i bought the MSD coil the directions mentioned a 0.8 ohm resistor so I bought it and installed it on my temp apron coil bracket. When i got stuck on Weds my son thought of the direct feed. He didn't want to leave it out on the street all night. So we grabbed a jumper wire and some of the wiring I had made for the resistor earlier this year. We wired 12 v from the battery to the resistor and a jumper from the other side of the resistor to the coil. It started but died like before. All we noticed is that the resistor got pretty hot. My big format wiring schematic shows the inline resistor. That very well could be the problem but just looking at the bowl of spaghetti under the dash difficult to spot it.
Regarding the tilt column i don't have any of the tilt electrical components, vacuum pump etc installed. i just use the manual tilt feature and not the swing away as it wasn't important to me. i now have someone who could get the swing-a-way restored and working but first i need to make the car dependable. The tilt column shouldn't have anything to do with ignition. The turn signal switch could be my issue with turnsignals but it doesn't make sense why the brake lights would be affected as they dont have anything to do with that switch. There is a Black with green stripe wire i believe 465 (?) which could affect almost everything according to the schematic.
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The jumper wire with 12V will work just fine to test, in fact when you have a original points system when you have the key turned to start there is 12V to the coil the help with a hotter start. Then when you return the key to on it goes through the ballast resistor to save wear on the points.
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Sounds like you may have more than one electrical problem. Don't discount TS switch relating to brake lights, the wiring does pass through the TS. At the TS plug, look for orange/blue (RH tail light) and Green/orange (LH tail light).
Often times can be the TS connector itself and not the switch. I had intermittent brake light problems that turned out to be the crimp connections on the wires at the TS switch plug. You have to pull the wires from the plug with special tool and recrimp and/or solder them to repair. Usually wiggling the connector will cause problem to come and go if connections are flakey.
I don't think the brake light issue is related to the ignition problem. I would try wiggling wiring and connections while the engine is running to try to isolate the trouble. Have you checked the engine gauge harness plug that runs out to the coil? This harness carries power from the pink resistor wire to the coil.
Just some thoughts - Kurt.
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Good points by both of you. What i can say is that this NOS switch crimped connectors didn't want to seat as nicely as the original or even the Scott Drake repop. The repop failed on the turn signal cam almost immediately and never cancelled from the start. That's why i went with the NOS unit at great expense. Not sure why the pins didn't want to seat but ultimmately had to lightly adjust the tabs with an exacto knife blade.
Well with the cluster out I started to look around and noticed that the connectors between harnesses in lower LH side of dash were not seated all that great. Flat black, red block and black block just not driven home tight. Couldn't do much by hand so took some channel lock pliers opened up all the way and carefully made a solid full connection. I saw the pink wire at one of these blocks. Im hoping this is going to make a difference. If the main harness ground is that tiny black wire with a internal star loop going to the LH side dash brace i got that one. Any more I should be looking for for the dash harnesses? I'm hoping tightening up the connector blocks is going to make a difference. The flat one seemed to have an 1/8" gap. Saw a lot of pins semi exposed.
The turn signal switch may need some additional work but I want to test it with the connectors fixed. Can i drive around without the cluster back in place?.
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As far as the intermittent ignition problems, it wouldn't be ground related. Have you bothered to change the condenser? It may be breaking down internally after it gets hot. I did see a vehicle like this too that the neutral safety switch caused a similar issue. I have noted that I have seen the feed to the coil as low as 5.3V with the key in the run position.
P.S. How did you relocate the coil to the right apron? I'd put things back here they belong, check voltage. If that is good, change the condenser. See what happens.
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Good points by both of you. What i can say is that this NOS switch crimped connectors didn't want to seat as nicely as the original or even the Scott Drake repop. The repop failed on the turn signal cam almost immediately and never cancelled from the start. That's why i went with the NOS unit at great expense. Not sure why the pins didn't want to seat but ultimmately had to lightly adjust the tabs with an exacto knife blade.
Well with the cluster out I started to look around and noticed that the connectors between harnesses in lower LH side of dash were not seated all that great. Flat black, red block and black block just not driven home tight. Couldn't do much by hand so took some channel lock pliers opened up all the way and carefully made a solid full connection. I saw the pink wire at one of these blocks. Im hoping this is going to make a difference. If the main harness ground is that tiny black wire with a internal star loop going to the LH side dash brace i got that one. Any more I should be looking for for the dash harnesses? I'm hoping tightening up the connector blocks is going to make a difference. The flat one seemed to have an 1/8" gap. Saw a lot of pins semi exposed.
The turn signal switch may need some additional work but I want to test it with the connectors fixed. Can i drive around without the cluster back in place?.
Loosely mated connectors can be a problem. You can drive without dash so long as you don't have a tach or bypass it if you do. No other grounds in the dash area.
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8 Barrel yes I did swap out the condenser already as that was mentioned by a local mechanic. Neutral safety switch may be original or a very old (25 year old) replacement. The coil was relocated using a bracket off a Miata. Initially i thought that the engine was really hot before breaking in the motor and heating up the coil. Just wanted to take that out of the mix. Having temporarily installed a real temp gauge the coolant temp stays in the 180-195 range with a slight spike to 205 if i get stuck in traffic or a RR crossing. Once moving it drops down. Once I take her out and if the problem seems solved I will reinstall the coil to the intake. I hate that I had to pull so much stuff like the original smog system to get even this far. Trying to set timing with the original smog pump in place is impossible.
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WOW! This seemed like something so easy to find when I first started reading this thread. Maybe try to KISS it. (K.eep I.t S.imple S-code)
The Neutral safety switch has NOTHING to do with the ignition system wiring at all! It only is a part of the STARTER circuit & Reverse light circuit. You can leave this idea out of the hunt.
I am with Marty on this one. If the wiring issue persists AFTER the squeezing of those connectors AND the checking of the under hood connection of the engine feed harness, try using a ballast resister off of a 1960's chrysler product and simply Hot Wire the ignition system between a direct connection at the battery and on the "+" (POS) post of the coil (by-pass the car's harnesses completely)and quit chasing your tail.
ONCE the car either stays running OR the car continues to stall out, THEN you can search in the correct area of the trouble.
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Rich,
The NS switch does interrupt the ability to start the vehicle. I assumed it cut the power from the solenoid as well. I've never had a Ford with an automatic transmission with the exception of a '66 Tbird. However, a ground isn't the likely culprit for intermittent operation.
-Keith
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Rich,
The NS switch does interrupt the ability to start the vehicle. I assumed it cut the power from the solenoid as well. I've never had a Ford with an automatic transmission with the exception of a '66 Tbird. However, a ground isn't the likely culprit for intermittent operation.
-Keith
Yes, on an Auto trans Mustang, it does interrupt the ability to start but it ONLY interrupts the "start" signal (from the key switch) to the fender-mounted solenoid. (an exception to this is the Tilt-Away column cars which have yet ANOTHER interrupter switch to the START signal, mounted on the column) On a MANUAL trans Mustang, there is a jumper wire (at the same underhood connection as an auto trans Mustang and is used to by-pass the switched "Park" or Neutral" signal, allowing it to start no matter what the gear selection.
On NEITHER manual or Automatic Mustang is there a 12V or 6V (resistor) circuit source going out to the ignition coil anywhere near the Neutral switch. On AUTO cars, the 4-wires that go into the neutral safety switch are two wires that are switched open/closed for "START" when in Neutral or Park and the other two wire are switched open/closed to supply the 12V to the backup lights. That is all. Nothing "magic" going on in that switch. This holds true for virtually EVERY classic Mustang without a starter delay. (Starter delay cars have a form of "magic" going on)
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And the weird part is a year ago I drove it 70 miles from my friends shop to home and it didn't exhibit any issue until I got on the side streets around the house after 65 miles of highway speed. Last week I drove it 2 days 50 miles each without a problem. But Weds and Fri it went back to its ignition missing and stall after 5 min and 40 minutes. I've had multiple drives of 25 miles in the neighborhood the last couple of weeks without a stall. I noticed the back-up lights weren't working Weds night. Electrical gremlins gotta love em.
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There is never an issue trying to start it when cold. The only time it is difficult to start is after its been driven and it stalls. Basically just driving along.....starts to lightly miss....and then shuts off and cruises to a stop. Once it shuts off it will crank and maybe even start and run but only for a few seconds. Not a fuel issue as you can look down the throat of the primaries and see fuel flowing down when giving it fuel with the linkage. Sometimes a mist appears but i assume fuel just vaporizing as it hits the hot intake manifold. I've chased the potential of engine heat and the carb for a few months. Aftermarket gauge shows nice normal engine temps. Carb idles at 625-650 rpm and 575 rpm in gear. Timing set at 6* BTDC. Mechanical advance at 26 degrees at 2000 rpm.No vacuum advance at this point. Engine Vacuum is about 15. Its the ignition misfiring that kills it. Just not sure why it starts. Seems electrical in nature.
Tighned up the electrical connection at all plugs. Started. Turn signals and radio worked for a few minutes but then they shut off. May try a drive later but not optimistic that she wont stall as its 80 degrees today. She prefers 60. KISS it? I want to kICK it. Not really.