Signal Light Wiring Diagram 78 Ford
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Discussion Starter · #1 ·
Somebody please help me out with my turn sigs. The problem is I don't have any. I have done all the normal stuff; new bulbs, new fuse, check the wiring for cracks or breaks, bad grounds and open circuits. Oh yeah, and my drivers side rear brake light is out, but only when the lights are on. All lights come on when I turn on the lights but when I press the brake pedal the that light goes out. If I can't get it figured out, what kind of shop should I take it to, body shop? This is killing me! :banghead
By the way: 78 bronco
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Have you checked out the flasher unit? Other than that you will have to get the test light and manual out and check the wiring. As you have no flashers at all by the sound of what you have written I would suggest the problem will be more than likely up to and including the indicator switch.
HTH
Tim
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Discussion Starter · #3 ·
The flasher unit being the round silver thingy right? Yeah replaced that also. The signal switch is in the steering column right? It has to that because my four ways still work.
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i think the four ways and the turn signals use seperate flasher units. I think mine are on the passenger side behind the glovebox somewhere, but in my 77 monarch it has two seperate units, four ways and signals
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Yes, turn & hazard flashers are separate. Check for power at the turn flasher - it should have 12V whenever the key is on.
The reason that light goes off is because it has a bad ground.
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time to get a meter or test light and test the socket. the PO on mine tried to find a short and messed the harness up and time killed the connection at the socket. does the 4 ways caus the lights to light (Flash)? if not the i bet socket or under the bumper connector (mine also had 4 -6 different trailer light connections). i whent to a junk yard and got new ones out of a truck.http://www.supermotors.org/registry/vehicles/detail.php?id=6364
you can see what i did.
mike
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Discussion Starter · #7 ·
I tested both round flasher units (relays?) with a test light, and only one has power. They are both under the column. At what point do the hazards cut into the circuit so I can test back from there? I am going nucking futs!
Thanks I'll keep trying.
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bigred, do the turn signals light up but not flash or not light up at all?
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Discussion Starter · #9 ·
They do not come on at all, not even a blip.
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I would start checking for power at the steering column harness. See if you have power going to and coming from the turn signal switch in the column. The harness plug is down by the column mounting bracket under the dash.
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The hazard switch (built into the turn signal switch assembly) converts the taillights from turn to hazard. You really need a good wiring diagram to diagnose them, because even Haynes has errors in this circuit for some years. 
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Steve83 said:
converts the taillights from turn to hazard.
Actually steve on the 78/79 and maybe the newer model's, not sure, I believe it converts the brake light circuit to a hazard. When you have the hazards on and step on the brake's it cancels out the hazards.
bigred said:
my drivers side rear brake light is out, but only when the lights are on. All lights come on when I turn on the lights but when I press the brake pedal the that light goes out
bigred tell us what exactly works and does not work. When you say the lights come on I take it you mean the parking lights? And when you step on the brake only the right side light's up and cancels out the parking light on the driver side rear? Do both brake's light up when the parking lights are off? Do the front turn signal's light up but not flash? Do the hazards work? We need more info on the problem.
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The brakes & turns use the same bulb elements, so it's almost the same thing. But since the change occurs inside the turn switch, that's what I say. The brake switch still functions normally, and will override the hazards, so it doesn't really convert the brake circuit.
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No turn signals.
The brake light going out is probably a separate problem caused by a bad ground at the light assembly. The turn signal failure is most likely caused by a wire damaged inside the steering column. You will have to pull the steering wheel off, and test at the turn signal switch itself. The hazzard warning lights are on a separate circuit, and use a separate flasher and wires up the column. If you find the wire from the turn signal flasher to the switch in the column is "open", you can jumper from the six wire connector "hot" for the hazzard lights (on the right side) to the "open" turn signal "hot" on the connector to the switch (on the left side). You will have to solder both ends of the jumper, keeping it as short as possible to avoid rubbing when you reinstall the wheel. The alternative is to replace the harness going up the steering column, which can be a VERY difficult procedure!
Good Luck!!
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Discussion Starter · #15 ·
Okay here we go, when the brake pedal is pushed, both sides light up in the back. When I turn on the lights, then press the brake pedal the drivers side brake light does not come on, the whole light goes completely out. The pass. side still works. Now for the turn signals, neither side flashes when the lights are on or off. But like I said before the hazards still work. I pulled the steering wheel off but cannot get the turn signal assembly off. There is a stud with a flared end preventing me fromm pulling it off. I don't want to grind it off, but it seems thats the only way to get it. Does this help a little? Thanks guys.
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:thumbup Check for power at the turn signal flasher with the key on,if you have power to the turn signal flasher,then jumper the turn signal flasher terminals with a piece of wire with male spade connectors,if the lights come on when you turn the signal swith to one side or the other(the side that you turn it to)note: it wouldn't flash at this time.then the problem is the flasher(as a way to confirm this,try the 4 way flasher in the turn signal flasher connector)you could try the flasher 1st, before trying the jumper if you want.If the turn signal lights still don't work, put the jumper wire in the turn signal connector/with key on,then check for power at the turn signal switch connector,if there is no power to the turn signal switch then run a new wire from the flasher connector to the turn signal switch connector,if there is power to the turn signal switch, then the switch either has a broken wire or is toast and needs to be replaced
Clear as mud? :banghead :goodfinge :toothless
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bigred said:
I pulled the steering wheel off but cannot get the turn signal assembly off. There is a stud with a flared end preventing me fromm pulling it off
The turn signal switch is held in place by 3 phillips screws.
I agree with bronco1, start at the flasher, check for power there. If you have no power at the flasher then you want to check the turn signal harness by the steering column.
You want these wires for checking power going to the turn signals:
green W/white stripe = left front
yellow W/black stripe = left rear
white W/blue stripe = right front
solid green = right rear
Check and see if you have power at those wires, if there is power there the switch is good and you have a problem with the wiring harness going to the turn signal socket's. If you have no power there then I would look for a bad turn signal switch.
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Did you get them fixed bigred?
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yeah im having the same problem my hazards work but not turn signal an replaced the flasher so now im checking out the wiring an so far it looks correct and good , my meter is outta batteries so i have to wait till tommrow an pick up a battry to cehck for power and see how that works out. I'll tell yeah what i found out if anything when i do
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I had a similar problem. But I had no brake lights either. Nothing no brake lights, no turn signals and no hazards. I knew the bulbs were good. I changed both flasher unit/relay( the round things) and fuses. They were all good. So I bought a new multifunction switch and put it in. Everything works great now. Pretty easy to install too.
Posted by: boydllorens.blogspot.com
Source: https://www.fullsizebronco.com/threads/no-turn-signals.31208/