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Turn signal switch wiring with Centech harness

JAFO

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Just sharing. Hopefully this will help others. If I find I have made a mistake I will edit later.

My Centech harness has a connector with letters. I will note the letter, wire designation and then the color of the turn signal switch wire. I installed a brand new turn signal switch purchased from Tom's Bronco Parts. None of the three color combinations noted in the Centech instructions matched the new switch wire colors, so I ended up ohming the switch to figure out where to connect the wires.

P - Stop switch - Green
N - Passenger stop light - Orange
M - Driver stop light - Green/red stripe
L - Turn flasher - Blue
J - Right front turn - White/blue stripe
H - Left front turn - Green/white stripe
D - Horn Power - Yellow (fat wire)
E - Horn (to the horn) - Blue/white stripe

Notes:
12v DC power is supplied to the horn from the steering wheel horn button. Mine is a 1973 and that year doesn't have a horn relay. I wanted a relay, so wired in one with one side of the relay coil grounded and then fed the other side of the coil with the yellow horn wire in the Centech harness. I found out after the fact that the Centech harness does have a relay, but I would need to modify my column, steering wheel, so that one side of the steering wheel was grounded. I didn't want to change my stock configuration in the column, so opted to install a relay out at the horn. Works fine and my column remains as a 73 would be configured.

L is the feed from the flasher to the lights when turning left or right. L is going to one of the center terminals on the turn signal switch. At each end of the turn signal switch is a front and back light, but for different sides of the truck. So when you are turning right, one end of the switch contacts to flash the front light and at the other end of the switch (opposite side) contacts to flash the rear light on the right side. This little tid bit helped me figure out how to land the wires.

I have notes at home of where the wires of the switch connect on the switch itself. I will edit later and put that in, which once I had ohmed those it really helped me to figure out where wires went.
 
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JAFO

JAFO

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Ha. Now mine has two. Darn I missed that about the harness. I guess I will undo all my fancy wiring under the hood. Thanks.
 
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JAFO

JAFO

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Wait, mine is a 1973, which does not have a horn relay from the factory. I am remembering now that I read something in the instructions about the harness is different for the different years. Years with a horn relay ground when you press the horn button. Years without the relay power goes through the horn button. On the Centech harness the horn relay is terminal G, which I do not connect on my year. I used D and E for the horn, so 12v DC was passing through my horn button as per that year. Anyway, I think I am correct and will leave the relay I installed. I guess I could modify my horn at the column so that it grounds when I press the horn and then I could use the Centech relay, but figure I'll leave it stock and have added a horn relay under the hood.
 

DirtDonk

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You might as well leave it, but you can also simply re-wire the connector at the column so that the power-out (Blue w/white) goes out to the relay's positive switching terminal (#86 usually), rather than to the horn directly like stock.
That's probably how you have it wired now to your own relay? But utilizing the Centech's built in relay instead.

You mention the colors not matching the diagram. I'm betting because yours was a '73 that your original wiring did not match the new turn signal switch's wiring either?
Too many changes made to that one particular section of the harness for '73 for some reason. I've found three distinctly different layouts all with the original switches.

Thanks for posting up the list. Should save a lot of people a lot of grief.

Paul
 

ransil

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the early years use a 12v feed to the horn button and when the horn button is pressed it sends 12v to the horn.

Later years use a relay when the horn button is pressed the horn button grounds the horn wire that provides a ground to the horn relay then the relay send 12v to the horn.

the early years should be able to be converted just need to ground on side if the horn button and remove/not use the 12 horn feed.
 
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JAFO

JAFO

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DirtDonk, you are correct, the old switch also had different color combinations that did not match the Centech notes. I ended up Ohming the old switch (since it was out and I could see all the connections easily), then transposed the wires to the new switch wires. It was a real pita working it out since it just is not something I have worked with much. Just don't think about the old turn signal wiring until something like this goes on.

I didn't want to modify the existing horn wiring in the steering column and opted to just install my own horn relay out under the hood. It works fine and I did no modifications to the wiring harness.

Got the steering column in last night. That was really tight getting my hands in to start the bolts up into the cowl.
 

JWMcCrary

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Found this thread when searching. The turn signal switch I bought matches the wiring from the first post. Prior to seeing this thread nothing lined up for wire colors in the Centech instructions or the diagram that came with the switch. I have the turn signal plug pinned as in the first post to connect to my Centech harness which has the horn relay. After reading this through, I'm wondering if this will work or if when pressing the horn button it will be shorted ???
 

DirtDonk

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What year is yours JW? Factory relay type, or not?
The good thing about the Centech is that the new horn circuit goes through a relay, so can be made to work with a grounded column or powered. The trouble comes when trying to interpret what Centech is trying to tell you in the instructions.%)
I've even hooked them up multiple ways and never blown a fuse or burned a wire in the steering column. That's the good news of course. The bad news is that... Your Results May Vary!!!!:eek:;D

The other good news though is that ultimately it is protected by a fuse, so in theory if you connect it in such a way as to short circuit it, you'll only be out a fuse or two.

Thanks for bringing this back up.
In fact, now that I'm thinking about it JAFO, I should have asked you before if you still have the original turn signal switch from your '73 laying around that you can take a picture of? If so, definitely document it. I'd like to see it myself, to keep track of those darn '73 wiring changes.
I've got one literally pinned out on a piece of paper with the wires taped in a row and their descriptions. This way it was easier to compare to the others I was working on at the time.
Kind of a pain, and not very durable when being battled around inside a tool box or electrical supply can. But it's been handy while it lasts.
I realize it's been almost two years. But hey, I've kept old junk in my garage for decades (centuries even!) without tossing them out.

Thanks. And good luck JW

Paul
 

JWMcCrary

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What year is yours JW? Factory relay type, or not?

Every wire in the bronco was removed and installing Centech harness and a new turn signal switch. The switch is JBG part# 17042, their site says 71-73. Not sure why I chose that switch, have had all these parts since 2012 just now getting it together. My other Bronco is a 73 so must have had it on my mind when I ordered it.

YEAR ??? haha, It has 68 tub, 75 frame, and 76 axles. The steering column is an older manual steering type. I took it apart and put new bearings, all the shift mechanism has been removed and the shaft cutoff and fitted for a WH lower shaft.
 

DirtDonk

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Hah! A Johnny Cash special, eh?
Since the column is what we're after at the moment, you have the 2-contact style for use without a relay (factory) that lends itself very well to the Centech harness.
I don't think you'll have any trouble once you've determined which wires are which. Since you bought the switch awhile back, and you say it matches JAFO's wire colors(?) then you should be able to make it work safely and securely. Just utilize the Centech's wiring and relay, and you'll be fine.

Your horn switch is a "pass-through" design, which means the signal, be it ground or power, comes in on one wire and out the other. So it really does not matter if it's 12v in and out like original, or grounded at one end.
If you keep it like original you have a 12v source in the Centech column wiring that can go into the column, then back out to the relay (I think they call it the "horn coil" maybe?) which will honk the horn.

Good luck.
I think I'm right, but you can use the old "trust but verify" method here anyway;D
Wait for someone else to chime in, but maybe start testing wires with an ohm-meter just to make sure.
You have Steve83's wiring diagrams to use as reference?

Paul
 

rydog1130

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I figured I'd ad to this post, here were the colors I came up with my AT column switch and centech harness. My switch came from JBGY

IMG_0107.jpg IMG_0065.JPG
 

DirtDonk

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Glad you got it sorted. These can certainly be a pain.
Thanks for posting up the orientation. I'm saving that for future reference.

The pic you posted is of a '74 and later automatic though.

Paul
 

rydog1130

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Glad you got it sorted. These can certainly be a pain.
Thanks for posting up the orientation. I'm saving that for future reference.

The pic you posted is of a '74 and later automatic though.

Paul

Yeah, I realized after that JAFO was referring to the old 3 on the tree column switch but It doesn't hurt to have the AT column on here in case someone is searching and is looking for it. The funny thing was about a week after I got it all figured out someone posted a new thread with all the wire codes sorted out, lol go figure!
 

Bronco1294

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Ok- having an issue. The turn signal switch I bought from bronco hut. Wires are LT blue/red, grn/wht, ylw/blk,wht/blue, LT blue, wht/Red, blue/ylw, Red/blk, and grn.

Any help appreciated!!
75 AT
 

DirtDonk

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Are you asking which colored wires do what? Don't your colors match the ones that JAFO and rydog posted up above? Seem to, but I didn't look at each one.

We can run each one down, but what wiring harness do you have? Guessing it's not factory then? If so, the switch colors would most likely match at least most of the wires on the truck.
Since yours is a '75 (thanks for including that by the way) then you should not run into the problem that many '73 owners have with varying mystery colors on their original units. But the aftermarket ones seem consistent. At least I hope they have not changed any!

If you're in need of diagrams in the middle of the night sometime, Steve83 here has some really nice ones on his SuperMotors pages, and the seabiscuit diagrams have been handy for many, many years. Don't have the link off-hand, but it's at "tripod.com" or something like that.

In the meantime, are you asking what each one does?

Paul
 

Bronco1294

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THX! New Centech harness. Colors don’t match above that I can tell. Blue/ylw for example.


Sent from my iPad using Tapatalk
 

JWMcCrary

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Ok- having an issue. The turn signal switch I bought from bronco hut. Wires are LT blue/red, grn/wht, ylw/blk,wht/blue, LT blue, wht/Red, blue/ylw, Red/blk, and grn.

Any help appreciated!!
75 AT

I feel your pain. I ended up just forgetting about colors. I traced out the wires from the switch and wrote down what each did and then matched that up with the way the wires were labeled on the harness.
 
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