'78 to '77 Steering Colomn Swap Wiring

[jckkys]

My '78 steering column has a different color code than the '77 harness. Has anyone swapped a '78 column into a late specifically '77 EB with an auto trans and got the wiring figured out? The semi circular plugs are the same so it's just a matter of putting the pins in the right positions.

 

[bronkenn]

If you scroll down these instructions you will see the color of wire and their designation https://www.americanautowire.com/PDFLink/92970069 510317 IN 8.0.pdf
Don't know if this will help

 

[Steve83]

Ford generally uses the same wire colors for a given function, regardless of year/model/options. So if you carefully trace each wire on the turn/hazard switch, you can probably get the connectors re-pinned to match each other. This shows the original layout:


(phone app link)

This & the NEXT several pages give the Ford wiring colors & functions:


(phone app link)

 

[jckkys]

Thanks Steve. The '76 is the same as the '77. I'd love to see the same kind of diagram for the '78. About 1/2 the color codes are same. The '78 has 2 contact brushes and 2 contact rings in the back of the steering wheel. One must be for the horn and the other could be cruise control. The smaller contact ring seems to be for the horn button. The other has no equivalent on the '77. The '77 horn wire is black while the '78 inner contact brush has a dark blue wire. The selector illumination light/wire is the same blue with a red stripe on both. Also there are green with orange stripe and orange with a blue stripe wires on the '78 that are nowhere on the '77 switch. So there is some but not total consistency in color codes. I have old worn out examples of both switches to disassemble.

 

[DirtDonk]

So yours does have cruise on the wheel? If not for that I would have said the two traces were the horn traces like a '73 and older Bronco. Unlike the Broncos, where every model had a horn relay after '74, the full size trucks still came both with, or without a relay depending on the setup.
Even though Ford had been using horn relays on pickups since the early sixties, my '79 for example did not have a horn relay. So I added my own.

If it turns out you have a 2-wire horn (which some of those wire colors sound like) then you can use them to trigger a relay with 12v rather than with ground like the factory did on your '77.
This might entail using a non-Ford horn relay, but that's a small issue.

With the addition of the cruise-control things change. Don't have my book open right now and both hands are typing and one eye is watching the timer, but I'll check my '78 diagram to see if I see anything that might help.
When I have both a hand and an eye available at the same time, I'll let you know what I find!%);D

Paul

 

[jckkys]

The standard color code chart says both contact rings are for the horn on the '78. WTF. The '76/'77s only have one ring and contact for the horn. It just feeds power to the horn relay. Why 2 wires? The horn always gets power it's not fed by the ignition switch.

 

[jckkys]

RockAuto lists a '78 Bronco horn relay that looks like the '74-'77s. Neither the '78 nor the '77 have cruise control. One, the (dark blue) wire is described as a horn switch control and the other yellow and light blue stripe is called a horn switch feed. How can they both work with a '77 harness?

 

[DirtDonk]

I've run into this before, where the wire colors on a '78 turn signal switch did not match the diagrams.
Maybe the Haynes diagrams are off. I'll check the '77 just to see if that sheds any light. But I don't pretend to understand the whole layout of this year switch anyway. Some oddities due to the cruise control that just don't compute. Maybe Viper or Steve would know, but they're Greek to me.
In the case of some turn signal and hazard wires, they are LOOPED between one side of the flasher and the other with the switch in the middle!

The '77 horn wire is black while the '78 inner contact brush has a dark blue wire.

According to the '78/'79 diagram, the only Blue listed (does not say dark or light) is the circuit in from the turn signal flasher.

Also there are green with orange stripe

This is one that I have seen before, but is not showing on the diagram.
Check it's function as the right front turn signal circuit though. That one is supposed to be Green w/white, so maybe it's discolored with age? Or are you working with a new switch in the column?

and orange with a blue stripe wires on the '78 that are nowhere on the '77 switch.

No Orange w/blue that I see. Gonna' have to test that one and let us know so we can put it in the diagrams ourselves.

I guess the best thing would be to post up a pic...

 

[DirtDonk]

'77 is the same. Sorry I could not catch the full page due to it being close to the binding. Basically the turn signal flasher is just out of the image.

Paul

 

[DirtDonk]

Yes, if both rings meant as just the horn circuit you have to treat it like you're swapping an old switch into your newer vehicle and re-wire the horn circuit as mentioned above.

With a normal Bosch-type relay (instead of the 3wire Ford relay) use the 12v that is fed in one wire and out the other wire to trigger #86 on the new relay. Other connections are standard with #30 Yellow from the battery, #87 out to the horn and #85 is ground.
Will work like a charm except you have to get rid of the factory relay. Not sure if that's a bummer for you, or you don't care as long as it works. But it can easily be made to work.

Paul

 

[jckkys]

Thanks Paul. I want to keep the harness as close as possible to OE '77. So the simple switch feeding the horn relay should be possible. I have both '77 and '78 switches that are no good to disassemble trace the wires. After seeing the cruise control diagram I'm glad I don't have that. I want to add the '77 is in the middle of a frame off. So I can't try out the various circuits'

 

[Steve83]

One must be for the horn and the other could be cruise control.

No, it depends how the truck is wired. Trucks without cruise can use both for the horn.

Also there are green with orange stripe and orange with a blue stripe wires on the '78 that are nowhere on the '77 switch.

Remember that colors can fade or change over 40 years. But it's also possible that there are functions (circuits/colors) that were removed &/or added, even between consecutive years.

I have old worn out examples of both switches to disassemble.

Trace each wire to find its actual function, and compare THOSE, regardless of wire colors.

Some oddities due to the cruise control that just don't compute.

It's not so much the cruise itself as the AVAILABILITY of cruise... It wasn't available on eBs, so no need for the wheel (sliding contacts) to accommodate cruise. But it WAS available on vehicles that use the same column as the '78 truck, so that column & wheel DO accommodate cruise. So the wiring changed slightly...
On vehicles without cruise, there was either 1) a "hot horn" (NOT grounded to the body) with 2 terminals (a hot & a switch both showing 12V when the horn was not blowing) going through 1 sliding contact ring on the wheel to ground on the steering shaft, or 2) a "cold horn" (with 1 terminal going to ground through its mounting tab) either triggered by A) a horn relay & its associated wiring to the wheel as #1), or B) a switch wire coming from 1 sliding contact ring via the horn switch powered by 12V on the other ring.
Those WITH cruise used 2A wiring for the horn, and the 2nd ring on the wheel was for cruise signals.

Clear as mud? %)

...the '77 is in the middle of a frame off. So I can't try out the various circuits'

Well, you CAN - you just have to plug it all together & add a "ground" wire that runs to each device & wiring ground terminal to get back to the battery negative. Jumper cables work, if you have several. I've helped a guy make his donor Mountaineer engine run on his eB frame with the wiring & fuel lines strung across the floor of his shop.


(phone app link)

Unfortunately (and like so many), that truck is still in mothballs...