My truck has been sporadically dying due to an open power circuit. As it turns out the 8 prong main disconnect has a problem. The one prong which protrudes from the firewall mounted half of the connection is broken off. It sticks out of the wireharness side a little bit, and a little is left sticking out of the firewall side.

Has anyone ever repaired a prong on one of these? I was wondering if it would be possible to use some 12 or 10 guage copper wire to create a core for the prong and solder the broken piece back on?

I welcome any and all ideas. Tried and true prefered, but all creative thoughts are welcome.

Thanks.

 

First off, do you know which wire/circuit this particular wire covers ??? If its not a resistor wire then I would push the part out of the dash harness back into the cab area. If it still has the male plug still firmly attached to the wire itself i would leave that part alone. On the other side of the issue, I would snip the wire back from the plug about 2 inches and solder on a longer female pigtail long enough to reach the male part in the cab. If there is enough plastic in the main disconnect plug itself to insulate against grounding out I would simply run the wire through the original hole.
After this is done simply plug the 2 ends together and carry on. a place you could possibly get a beefy single wire connector is the license plate light. There are other places in other period Ford products that Im sure you could get this connector from as well.



I hope this helps, cs65


if you can, post a pic of both sides

 

I think it is the resistor wire, which is why everything goes out when the contact in the connection is lost. That is the primary electrical supply. From my study of the wire diagram it shows the resistor wire starting at the disconnect and running to the ign. switch. The implication is that the wire in the engine compartment wire harness is not a resistor wire (regular stuff).

The connector has eight prongs. One of them is the opposite sex of the other seven on either half of the connector. It is that one that is broken. It looks like it got corroded (green on the otherwise silver colored prong), weakened and eventually snapped when tugged on. Now a little vibration from running down the road is enough to open the circuit.

Thanks for the advise. I'll pull the mat back and try to find where it will push back into the cab tonight.

 

Title: main disconnect at the firewall

Title: Connector-firewall side

Title: Connector-harness side

Title: Connector-Firewall from inside cab

 

Purchased wire harnesses thru Mr. Mustang, Inc. who make reproduction wiring harnesses for the 64-67 F100's. The headlight harness plugs into the main disconnect at the firewall but don't see the other main disconnect circuit on their list. Certainly can see from pic's why you were experiencing electrical shut down. Have not found anyone who manufactures reproduction harness for the instruments, or the circuit in question, but curious if that particular harness is reproduced for an early model Mustang perhaps Numbers Dummy would be able to advise. Strongly suggest purchasing the Ford Truck wiring Diag Manual, found extremely helpful, majority of the Ford parts supplier's carry them for $10-$15, don't purchase the laminated type. Purchased mine thru FTE 'Motorhaven' parts shop, this was quite a few yrs. back, believe there is a new FTE parts supplier and not sure if they carry them. Can go to the source thru Jim Osborn reproductions.

 

does your truck have the extra alt and oil prerssure gauges on the outboard ends of your dash cluster ?? I have a full harness Im looking at now out of the truck...


- cs65

 

The instrument cluster doesn't have the ALT and Oil Pressure guages, not that I'd be opposed to enhancing the complement of guages.

I've got some wire diagrams printed off the web. Mostly for 1964, but in this area there pretty close. I'll keep an eye out for a wire manual though.

Other than redoing the under dash harness, no ideas about just swapping out the one prong? Under the dash rewire seems pretty drastic.

Are the prongs cast in the rubber or just pushed in? I'm a little reluctant to mess with it too much since I can press it together good enough to run it now...but I know that won't last.

Thanks for the help.

 

The resistor wire is not part of the wiring harness, it was sold separately.

C0LF-12250-A .. Resistor Wire-Ignition Switch to Coil (Motorcraft DY-37)

61.49" long / color coded Pink / #20 gauge wire / 1.30 - 1.40 ohms resistance / Fits: 1960/72 all cars/trucks.

 

Does that mean that I can replace just that wire, through the connector with a new prong showing on the engine compartment side? Or does the wire disconnect from the wire set in the connector (see the 4th picture earlier in the thread)? I'll try to take a closer look under the dash tonight, but its hard to fit my head up there. Taking that picture was none too easy either.

I just called a local towing company I happened to know had a 65 partially parted out last year. It's still there and the harness under the dash is mine for the taking (read my labor) + $40 to $50. Sound like a good deal? It would include the resitor wire. A spare might be a good thing to have around.

 

If you need it and they got it yeah it sounds like a good deal. Get everything you can get and don't cut any just follow them all the way to the end and snag what ever is attached for spares. Bring some extra cash because you'll find something else you need in that parts truck. It happens to me every time.

 

This wire IS NOT NOT NOT the resistor wire...as I said I have a hardness in front of me.,..actually 2...but this wire runs from the plug at the firewall up towards the ignition switch...before it gets there it splits...at this place there is what I believe to be a fusible link. Its a large black rubber encased piece. coming out of this piece is 2 yellow wires...one runs to the ignition switch and the other is a feed for the alternator accessory gauge package which include the oil pressure gauge commonly found on custom cab trucks.
In looking at the location of the resistor wire(pink) this wire is wrapped mostly on the outside of the main harness and is encased in cloth sheath. The location of this wire on this plug is on the opposite side and in the 2nd row. You can plainly see it and feel the difference as its a resistor wire at the plug.
This wire DOES NOT connect to your problem plug!!!! Leave this wire alone entirely.



Im gonna go cut a junk harness apart and show the wires, etc...hold tight folks...



- cs65

 

Heres the skinny on the tracing of this plug inside the cab...
Before I get to that though...on this parts truck...if the ignition switch wiring has been cut, altered or whatnot...avoid it like the plague...

This wire from the broken prong rearward into the cab goes into a fusible link as a black with yellow tracer...it is the largest gauge wire in the entire in cab wiring harness. At this fusible link, which is taped up in the harness entirely, is a large black rubber coated piece with no plug ins or anything like that. At the end where the black with yellow tracer wire goes into the f/link there is another wire that meets there as well...it is a smaller gauge red wire with no tracer. This wire goes to the fuse block on the cigar lighter circuit which is covered by a 14 amp fuse.
From the fusible link going through it, it becomes 2 yellow wires...smaller gauge. One goes into the rubber plug at the back of the ignition switch. The other yellow wire also of the same gauge is the feed for the alternator and oil pressure gauge harness offered as an accessory but more commonly found on Custom Cab trucks as I stated earlier...the feed wire ends in a female plug which is left loose with about 2-3 inches hanging out of the harness wrapping.
Removing this harness is a royal PITA!!!! The ABSOLUTE hardest part to undo is removing the 2 phillips screws securing the fuse block to the firewall. The ends of these screws can be accessed from the outside as far as wirebrushing, lubricating, etc. for removal. One is way up inside the deep recess of the fender apron and the other is diagonally about 3-4 inches from it. How do I know this is a PITA to remove...cause i have done 2 in the last month and over time a total of three..I dont cut wires or destroy parts like the fuse block during removal as these are hard to locate parts.
The other hard part is removing the main disconnects from the firewall itself...there is 4 tiny spring loaded clamps which when put in the firewall hole simply snap in and are indeed a tight fit...rememeber...its gotta be water and air tight...in undoing these be very careful around the master cylinder brake line...you will need to use a 6-8" medium blade width straight slot or flathead(whichever name you prefer) screwdriver and a small hammer...using your palm will hurt like he** as these clips dont just give and relax...its the kind of thing that if you get one unlocked and go to another one in the course of working the 2nd one the 1st one you had unlocked, will relock itself back in the hole...Its an annoying pain in the royal keester...on the trucks I have done I have removed the master entirely...BUT remember...you gotta remove it in the same way you will be on your truck...that way you know what you are going up against and learn tricks and so on...The 1st of 2 trucks I did last month the entire nose and brakes and steering column and hood hinges was off...a totally bare firewall...and they STILL fought like a son of a gun...
when unplugging the underhood harnesses from these also, pull carefully straight out...wiggle or twist lightly, just to break the grip the rubber has had against itself for 40 plus years. If the area is greasy and all that...clean the area thoroughly...the tabs you gotta unlock on the cab harness are about 1/16-1/8" wide...very very narrow and hard to see if you dont know what you are looking for.
With the fuse block loose and firewall disconnects undone and loose from the firewall itself...the rest is fairly straight forward...TAKE NOTES, PICTURES...AND LOTS OF THEM!!!! The diagram book that they sell for about 10 bucks or so of which I have is NOT 1000% correct...and thiis is to the best of my knowledge a FoMoCo authorized reprint...plus its vauge on wire colors and so on...Remove the battery cables first and make sure they wont spring up and inadvetantly make contact with the battery...
AS for the in cab stuff aside from what I mentioned already...if you have a bad back or joints or other ailments...get someone to do with you supervising or be ready to spend the better part of a day pulling it apart...First off...look at the firewall insulation pad..it is the black hardboard part that runs side to side inside the cab and everything from the dash runs through it...IF it is a good pad...get it...I need one very badly...If its bad as is common, proceed as planned...if the truck is a 4 speed, remove the steering column entirely...2 plugs at the lower jacket go to the main harness you are removing...removing the column will give you loads more room to maneuver...you will be turning your body into pretzel like positions and shapes...just so you know...aalso, to remove the column, there is a 12 point 1/2" bolt between the rag joint and the steering box...remove this and with a flathead screwdriver twist a lil bit to spread the coupler and then twist between rag joint and steering box working the rag joint off of the box...just twist it loose first and then when the column to dash bolts are removed you can tug on the column and it will slide off usually...when in the truck and pulling the column...grab around the mast jacket vs the steering wheel....especially if the wheel isnt cracked or cracked badly. if the firewall pad is good, undo the rag joint from the steering shaft and set aside...if its good it would be a good thing to snag as a spare. Then after the r/joint is off of steering shaft, slide column straight out and set aside.
Now you can go for the cluster...undo the screws of the bezel and wiggle the cluster away and you will see the array of wires and such...If this parts truck has the plastic sweep speedo used on Custom Cab trucks be gentle...an uncracked bezel is a nice thing to have as well...rolling the top rearward you will see blade plugs for the instrument cluster voltage regulator at the top almost at the center...it has 2 plugs on the regulator itself and a ground wire on top of it which is attaches to the metal cluster base itself. undo the dash lights...they just pop in...push to the side a bit and they will simply pop out. The alt and oil pressure gauges, if so equipped are 3/8" nuts...2 per gauge. the other gauges for the main cluster(fuel and temp are 90 degree push on plugs...like the brake light switch wires which are also part of this harness and need to be undone and shoved back through the firewall with their 1/2" rubber firewall grommet. Unscrew the speedo cable...should be able to do that by hand. there are 2 straps , one on the cluster itself on the passenger side of it...lift harness out of it and cluster will be in your hands..handle with care...esp. if its a good plastic bezel.
Switches...wiper switch has 1 or 2 molded blade plugs...pull to the rear of switch and it will slide off...theres no lock tabs on its wiring. Heater switch...same thing...pull rearward. same for the 4 way flasher setup if so equipped. The light on this is same type as dash cluster bulbs. The bezel, once wire is away, is a push and twist to release setup...like tail light bulbs.
Cigar lighter is a 90 degree push plug like brake light switch wiring...it can be a tight one at times to remove. The cigar lighter light(silver shroud on top of lighter well) you need to push one side of the silver cover inward and raise up and it will be free...it has a metal tab on either side that fits into lighter well...can be removed by grasping either side and squeezing and raising up.
Lights...this can be done 2 ways...one way you get the switch itself too w/o undoing its wiring...pull light switch to on position...depress button on top side of rear of switch on metal part and remove handle...slides right out. With **** out, use a large flathead/straightslot screwdriver to unscrew the switch to dash nut and the switch will fall away when undone...there may be a metal U shaped spacer between the switch and the dash...keep this spacer ...
Ignition switch...you will need the key to do this properly...it cannot be done properly without it...if theres no key, unscrew a door access panel and remove a door lock as it will have the key code and get a key made.
With key in switch, turn to accy(full twist counterclockwise) get a paperclip and insert in tiny hole near key slot...keep key in this position and with key in accy position, push the small button in the small hole with paperclip and when button depressed turn key further counterclockwise and remove lock cylinder...put the lock cylinder on the dash top.
With the lock cylinder out, push on the backside of ignition switch while holding bezel in place twist and it will pop out and will have bezel and switch in hand.
Now there are 2 wires which run up the windshield post on driver side...fuel sending unit feed and dome light feed wire...these both have male/female round connectors like the broken prong ...fuel sending unit is orange...it can be unplugged near the fuse block and bulkhead disconnect area...its the only orange wire there...The dome light has the same type of plug in connector...it is a black with dark blue tracer...its pigtail is near the back of the ignition switch...it is the only plugged in wire aside from the resistor wire(pink) which as noted prior is taped to the outside of the harness mostly. Unplug the black wire with blue tracer and this should be everything...the wipers on this harness will only have the power feed...its switch wiring is part of the motor assembly. if the truck has electric windshield washers, unplug the switch above ignition switch. The washer button switch just pops in the hole. unplug it and the wire from the washer pump under the hood and snake back through the firewall.
If the truck had the extra alt and oil pressure gauges, the rest of its harness needs to be undone from under the hood...its end is routed to the junction block and starter relay on the RH fender apron.
Also, if you have the extra gauges, the gauges sending unit wire runs up near the oil filter and is a red/white resistor wire with a push on type plug.
Lastly, you need to unplug the headlight dimmer switch which is a push on blade type connector which will slide off to the side.



This is pretty much it....alot of info I know, but this will make your job alot easier..if you have any questions, dont hesitate to ask for pointers, etc. or email me if you wish.


- cs65

I wonder if this is the longest reply on here....LOL

 

slick, being the connector "ain,t no good the way it is"you might try cutting the black wire at the connector on the engine harness side. than hold the black connector with visegrips and try to drill threw the hole where the broken connector is. if that works try it threw the fire wall side. if you can clear the holes you can splice the wire pass it into the eng side of the harness and threw the fire wall and splice it back to the dash harness.i have done this with the plastic connectors without any problems,but i never tried it with hard rubber connectors.scope it out if you think it might work for you great, you got nothing to lose.

joe

 

CamperSpecial65, Can't thank you enough for the wealth of information. If that pad is good and I can get it for you it's yours. Don't know what it'll cost, but if its more than nominal I'd be surprised. Mine is really good (I think) so I'm not personally interested.

You may have posted the longest reply in the, what decade, this site has been up? I had a whole beer get warm while reading it .

I'll be printing it out when I go to visit the donor. Last year when I saw this truck I went to look at a 64 F100. Running and all, but the roof seams were all rusted out with big 2" wide open to the sky holes. I can't fix that kind of stuff. So now I've got the 65 (preferable IMO for the Twins).

I have repro manuals, vols. 1-3, but not the wires or body assembly books. Nothing I've read explains how to get the rubber connectors out of the firewall. I've been tempted to try to push from under the hood, but now I'm really glad I didn't.

I'm going to bring a copy of your post with me when I get to the parts truck. I'm not too bad with that digital camera, so plenty of pictures will be taken. If the wiring book doesn't explain exactly how to remove/disconnect/ unassemble this stuff, perhaps its time to submit a detailed how-to article. Clearly, if you've done two in the last month, there's got to be a lot of folks who have had to learn this the hard (and expensive) way, trial and error. Where trial = hard and error = expensive. Anyone doing frame-off work would need to know this too.

And if reproductions of this harness are not to be found, proper extraction is a practice that should be encouraged at every termial point. As you mentioned early on, if ends (ignition switch) are just cut, skip it.

I'm supposed to be out of town this weekend (too bad too, the weather is supposed to be dry and in the seventies...perfect for yarding), so it may be a couple of weeks before this operation starts.

But I know what to do when the truck stops now and I know how to arrange for a permanent fix. The donor truck is in a really small yard. There is a huge antique yard that is also close by. I used to go there 15 years ago to find stuff for my 62 Lincoln. Unbelievable place. I haven't checked it out for Slicks yet, but you bet I will this fall. I'll report back what I find.

Thanks again.

 

Joe, Great creative solution. Just what I was fishing for when I originally posted my question. It certainly sounds much easier than pulling the replacement harness out of a donor truck, but if I can get the originial equipment to replace the damage I will. My truck is seriously unmolested, all original and just needs someone to take care of it. But really good suggestion. Thanks.