Need Rewiring Help

Darrell S

Darrell S

Senior Member
I am starting to rewire the 48. Must say I am intimidated as I have never done this before. I have all new wire from Sacramento Vintage Ford.

What is the best way to rewire under the dash? I have removed the front seat for better access. Even getting to the places to disconnect the old wire is problematic letting alone installing new. I would like to hear how others have accomplished this job. Dashboard removal?

Helpful comments much appreciated.
 
I stacked up pizzaboxes, put a boat cushion on top with the seat in when I had to fix wiring under the dash of a packard----but they were high class pizza boxes, not dominos
 
DISCONNECT YOUR BATTERY and then.....

First. Take plenty of BEFORE photos, including close ups, of the original wiring as it is now in the car.
Second, Attach labels to each wire end telling what it originally attached to under the dash.
Third. Don't cut of any wires. You want to leave the OEM harness intact.
Fourth. Gently remove the harness in one piece, if possible. If you have to pull the wire connectors apart label them first.
Fifth. Lay a nice thick blanket or padding on the floor with a pillow for your head. More space if you can remove the steering wheel.
Sixth. Lay the old harness on the garage floor along with the new one and see if it matches.
Seventh. Install the wiring through the firewall first and then wire the dash. Don't forget the dome light wiring.

Of course you want plenty of light to see what you're doing and keep your mouth closed so you don't end up choking on some nut or bolt that falls on you when under the dash.
 
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The replacement wire harnesses come with wire covering for which the basic color and trace color match that called for on the Ford wiring diagrams. That makes it easy to know which wire goes where, but just to be sure, take pictures of the routing of every connection under the dash before you remove the wire.

Access is tricky at some spots but all connections can be disconnected and reconnected without removing the dash, - if you are under 80 and 300 lb. You might consider disconnecting the clutch and brake pedal clevis so you can drop the pedals to the floor. You will need bright lighting with some means of hanging or clipping the light. It will also help to have one of those headband mounted lights that you can aim by moving your head.
 
drolston said:
The replacement wire harnesses come with wire covering for which the basic color and trace color match that called for on the Ford wiring diagrams. That makes it easy to know which wire goes where, but just to be sure, take pictures of the routing of every connection under the dash before you remove the wire.

Access is tricky at some spots but all connections can be disconnected and reconnected without removing the dash, - if you are under 80 and 300 lb. You might consider disconnecting the clutch and brake pedal clevis so you can drop the pedals to the floor. You will need bright lighting with some means of hanging or clipping the light. It will also help to have one of those headband mounted lights that you can aim by moving your head.
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I just turned 80 but not up to 300 lb quite yet. I have not cut any wires but someone has been here before and done some of the darndest things with wire that one can imagine. I don't know why as the only thing added are aftermarket turn signals. Every thing else is stock. The wiring to the heater is cobbled along with the radio and there is much added wire that is dead ended or does nothing. Looks like fun. Good ideas about pictures and clutch-brake pedal disconnects.
 
Kinda like the pizza boxes, I have used a homemade platform made of wood. Put it next to the open door and put a cushion on it. Then old blanket or carpet piece on floor. Definitely saves the back when under the dash.
 
I took the front seat out then I took the dash out sat it on my knees while sitting on a milk crate !! It was pretty easy and I hate wiring !!
 
coolcoupe said:
I took the front seat out then I took the dash out sat it on my knees while sitting on a milk crate !! It was pretty easy and I hate wiring !!
Click to expand...

I'm liking that idea!

There was a thread on connectors for the bullet wire ends. What is the best connector and crimping tool?
 
Stock connectors are push fit and do not need crimping; - unless the fit is a bit loose, in which case a little pressure with pliers before connecting will tighten things up. Regarding the added wiring, the turn signals alone can add eight wires. Those are generally color coded, so pictures of those connections will be helpful.

Regarding wiring for heater, radio and other added accessories, - you do not want all of that current going through the ignition switch. I added terminal strips for power and ground high on the firewall (out of sight). Tapped battery power from the battery post on the circuit breaker panel through a 30 amp fuse to a accessory master power switch on the bottom edge of the dash, and then to the terminal strip. Thence to radio, Sirrius receiver, heater, GPS, etc.
 
drolston said:
Stock connectors are push fit and do not need crimping; - unless the fit is a bit loose, in which case a little pressure with pliers before connecting will tighten things up. Regarding the added wiring, the turn signals alone can add eight wires. Those are generally color coded, so pictures of those connections will be helpful.

Regarding wiring for heater, radio and other added accessories, - you do not want all of that current going through the ignition switch. I added terminal strips for power and ground high on the firewall (out of sight). Tapped battery power from the battery post on the circuit breaker panel through a 30 amp fuse to a accessory master power switch on the bottom edge of the dash, and then to the terminal strip. Thence to radio, Sirrius receiver, heater, GPS, etc.
Click to expand...
I run everything thru my ign. sw including heater motor, CD / amp, elect. wipers, halogen lights with no problems. Has been this way for about 20 yrs. Those switches are pretty robust.
 
fordor41 .... you're lucky. The feeder wire to my ignition switch got so overloaded/overheated its insulation melted. It had those extras on it .... heater, radio, directional's, elec wiper motor, fog lights, etc. Lucky the bare wire did not touch a part of the car body and arc-out. Could have had a fire.

I fixed it with a small 8-circuit flat-blade fuse board for those extra's. Fed that from Batt but operated it by a relay off the ignition switch. Now each extra has its own fuse and it took all the load off the ignition switch. The motors and other devices work a lot more responsive now. Not OE but I feel a lot safer now.
 
Im with Drolson and DrBrown. The wiring on a Ford is very straight forward. (I suppose my 32 was maybe a little more basic?). I bought a wiring loom which was excellent quality and it came with very clear instructions. Mine was split into 2 parts, basically behind the dash and under the hood.
I took the front seats out, but the gear stick is a bit of a pain.
Most wiring has been screwed about with, certainly mine had, so it felt great to replace with nice new braided cables. The only real change to original was a relay for the lights, which is fairly easy to wire in using the new loom.
What I think is missing is a good fuse system. I think mine had one between the ammeter live side and the light switch. I did something similar to DrBrown.
I stayed on 6volts, and with good grounds and new connections, and the relay, the lights work very well.
I did leave the dome light and rear light cables in place because they were in good nick/hard to get at (dome light).
 
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I found someone had added a wire other than stock that went to the clock (which doesn't work anyway) and then leads to an original wire going up into the right windshield post. I'm wondering if this is the wire to the courtesy lights? The way the heater was wired really has me confused. When I first got the car this wire shorted out so I disconnected it.

After having so much of this old wire come part it is no wonder the turn signals were part time and the dimmer switch caused the headlights to almost go out. This is a job long overdue.

I really didn't want to tackle it myself but scheduling with my good friend and wiring guru didn't work out. I am hoping he is available if I run into snags.
 
The earlier cars may be doable with the dash in but my 51 Mercury cars were impossible. It was much easier to remove the dash. This way you can easily get the instrument stuff and the fire wall carry through in place and looking good then plug all the circuits together & install the dash. I put the radio back in after the dash is in place. The steering column had to be dropped down but that was the worst of it.
 
Darrell, That wire going up through the right windshield post goes to the courtesy light switch.
 
Can someone enlighten me on how to remove the light switch from the dashboard? I have the ignition wiring harnesses separated from the lighting harness and I need to drop the switch down from under the dash to be able to get at it.
 
I assume you mean head light switch. If so, I loosen the bezel, to give some room, and reach up between the dash and switch assy. there is a metal tab around the pull knob shaft. depress the tab, towards the switch assy(if I remember correctly) and the shaft should pull out. then assy can be dropped out. Can be a b***h! I found a NOS switch on ebay so I could figure out what I was looking for!
 
fordor41 is right and yes its very tight up around the HL switch. Think I accidentally disconnected more items than the HL switch. Be sure the Batt is disconnected !

Only difference I found with my '47 was that there was a small slot on top of the switch into which I had to insert a tiny screw driver to get the pull knob shaft to release. My Ford manual shows how. I replaced mine with a NOS '46 switch (identical except for color of circle on knob - switched them) found at the HAMB classified.
 
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