Need Rewiring Help

[Darrell S]

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.

[Kurt in NJ]

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

[19Fordy]

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.

[drolston]

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.

[Darrell S]

Originally Posted by drolston

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.

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.

[RalphM]

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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.

[coolcoupe]

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 !!

[Darrell S]

Originally Posted by coolcoupe

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 !!

I'm liking that idea!

There was a thread on connectors for the bullet wire ends. What is the best connector and crimping tool?

[drolston]

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.

[fordor41]

Originally Posted by drolston

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.

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.

[Drbrown]

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.

[Tom Walker]

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).

[Darrell S]

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.

[rotorwrench]

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.

[19Fordy]

Darrell, That wire going up through the right windshield post goes to the courtesy light switch.

[Darrell S]

Originally Posted by 19Fordy

Darrell, That wire going up through the right windshield post goes to the courtesy light switch.

Thanks 19Fordy, one less to wonder about.

I am always envious of the pictures of your engine compartment. Beautiful!

[Darrell S]

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.

[fordor41]

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!

[swoopNZ]

Call an auto electrician - you won't regret it.

[Drbrown]

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.

[Darrell S]

Thanks to fordor41 and Drbrown I was able to remove the headlight switch. I had the gauge panel out and was able to see the top of the headlight switch and the small slot to insert the screwdriver. I don't know if I could have removed it without being able to see the top of the switch. Thanks again

I have almost all of the wire under the dash installed, waiting for new 6 volt light bulbs to come.

I am having a time with the heater wiring. I have the harness that leads to the heater motor from the small control panel to the right of the steering wheel (where the pull knob for the defroster is). I have no wiring diagram or wiring harness that shows how to connect the 2 heater switches that are on the left side of the steering wheel to the small panel on the right side. I have searched the forum for information on this but no results as yet. Anyone familiar with this?

[jimTN]

I have had the heater switch explained to me and have slept since then. It has provision for reversing the motor for defrost. There was a posting that had a 40 switch which is sort of similar but not the same. Maybe someone will post the correct diagram this time for 46-8.

[big job]

Originally Posted by Darrell S

Thanks to fordor41 and Drbrown I was able to remove the headlight switch. I had the gauge panel out and was able to see the top of the headlight switch and the small slot to insert the screwdriver. I don't know if I could have removed it without being able to see the top of the switch. Thanks again

I have almost all of the wire under the dash installed, waiting for new 6 volt light bulbs to come.

I am having a time with the heater wiring. I have the harness that leads to the heater motor from the small control panel to the right of the steering wheel (where the pull knob for the defroster is). I have no wiring diagram or wiring harness that shows how to connect the 2 heater switches that are on the left side of the steering wheel to the small panel on the right side. I have searched the forum for information on this but no results as yet. Anyone familiar with this?

confused; 2 heater switches on the left? never seen that must have been
added on in the past or a under the seat heater?

[Darrell S]

Originally Posted by big job

confused; 2 heater switches on the left? never seen that must have been
added on in the past or a under the seat heater?

I am also confused. I wonder if there would be anything about this in service bulletins? Or if someone with a 46-48 has these also?

[fjz]

Darrell: I am in the process of installing new wires in all of my 48. My dash is out and I wouldn't attempt to do it otherwise. My ignition switch,original column type, is also out and I am trying to determine which post is power, accessories and ignition. Also how does it come apart so it can be re-installed in the column once the dash is back in? All help would be much appreciated. Regards Frank

[Darrell S]

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Originally Posted by fjz

Darrell: I am in the process of installing new wires in all of my 48. My dash is out and I wouldn't attempt to do it otherwise. My ignition switch,original column type, is also out and I am trying to determine which post is power, accessories and ignition. Also how does it come apart so it can be re-installed in the column once the dash is back in? All help would be much appreciated. Regards Frank

My ignition switch is mounted in the dash and I don't have the column lock. My switch was marked at the base of each post. I would like to know how the little stainless bezel on the ignition switch attaches. It was never on tight since I have owned the car.

I did mine lying on my back. I did remove the gauge panel, ignition switch and light switch though. It is all back together under the dash except for the heater which I had to order some connections for. I am now working on the lights. I had to buy other stuff for the tail and parking lights as they suffered from lots of rust and I didn't want to reuse them. Good luck on your project.

[Darrell S]

I had to stop on the wiring job due to other things that needed my attention. I am back at it again now with mixed results.

The lights work well and the horn never sounded this loud before so I am good with that. However when I turn the ignition switch on there is no movement on battery gauge to indicate any draw at all. The starter engages and the engine turns over but doesn't want to fire. The only gauge that moves is the temp which goes to cold immediately. (gas gauge not connected yet) When the lights are turned on the battery gauge shows no drop either. I have checked and rechecked my wiring diagram and the color coded directions.

Any suggestions on what I am missing?

[Bob C]

Couple of questions, Is the yellow wire running through the loop on the ammeter and
have you tried running a hot wire directly to the coil just to see if it will fire??


Bob

[Darrell S]

I did check for spark and it was good. It has not run since January so I gave it a shot of starting fluid and off she went, running nicely. The battery gauge is still not working though and the yellow wire is running through the loop. Should I change direction on the yellow wire?

Now off to see if I can hook up the turn signals.

[rotorwrench]

The induction meters were good units but they can wear out like anything else. The only other thing I could figure is that there are two big yellow wires that go to the bus board. The one that comes from the battery connection at the starter relay is the one that goes through the loop on the back of the induction meter then on to the bus. The one from the voltage regulator Bat terminal goes direct to the bus board. I don't know if it's even possible to mix them up but I figured I'd mention it anyway. If it no worky then it no good.

[JSeery]

And to add to rotorwrench, reversing the wire should not make any difference as far as showing that the gauge is working. Reversed polarity would just deflect the needle in the wrong direction.

[Darrell S]

Thanks guys for the gauge info. I did run the wire in the other direction but it made no difference. I am wondering why it worked with the old wiring harness but not this new one.
Does someone offer a 6 volt battery gauge that will work? I'd like to know what the system is doing or not doing.

[JSeery]

Anyway the loop was damaged when the old wire was removed?

[Darrell S]

Originally Posted by JSeery

Anyway the loop was damaged when the old wire was removed?

Not that I am aware of, it looked the same. Is that loop just wire or something else?

[Darrell S]

Would this kind work, the back is different?

[Newc]

wow; Watch out for '47-48 changes. Tyee sent me three secmatics and none matched my Nov '47 manufactured '48 Canadian Merc. Totally odd car newc

[Darrell S]

Originally Posted by Newc

wow; Watch out for '47-48 changes. Tyee sent me three secmatics and none matched my Nov '47 manufactured '48 Canadian Merc. Totally odd car newc

This 48 is Canadian too, I have found some differences. New wiring harnesses did OK though.