70 bronco blinkers and hazards not working

zachjb95

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im working on my 1970 ford bronco thats having a wiring problem i cant figure out. so the issue is the blinkers and hazards don't work. all the other lights work fine .also the front blinkers and blinker indicators on instrument cluster turn on solid when applying the brakes. anyone else encounter this issue or no what's wrong and can help would be much appreciated
 

Tiha

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Sounds like you have a bad ground wire on one of your brake/tail lights.

Pull the housings out and check them, clean them up
 

blksn8k

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Have you confirmed that the round flasher thingy under the dash is good?

Also, something that I encountered when I installed fiberglass quarter panels on my '75 was that the taillight housings themselves are part of the ground. In other words, for any bulb that is plugged into the taillight housing there is no separate ground wire. Make sure that the taillight housing itself is grounded to the body which I believe is actually through the mounting screws since there is a gasket between the housing and the body that acts as a water seal.

On mine, because there was no longer a metal body part to act as the ground since my taillights are now mounted to fiberglass, I did have to add a separate ground wire from each taillight housing to a steel part of the body. I just used the same ground screw that was already there for the side marker lights since they do have a separate ground wire and the ground screw just happens to be right behind the taillight. As a last resort, I suppose you might need to do the same thing.
 

zachjb95

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All the ground wires same fine for the brake lights and I've looked and I've not found one of those round flashers underneath the dash
 

Tiha

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I suppose it could be a turn signal switch, but back feeding into the other lights is usually bad ground.

Maybe grab a test light and see if there is power back there? with your food on the brake.

Do your tail lights work?
Reverse lights?

I was thinking the flasher was right underneath the hazard switch, hanging by the wires under the or behind the dash.

If you replace the flasher with a jumper wire it will turn the brake lights on and keep them on. That might help you troubleshoot with a test light.
 

blksn8k

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Here's a wiring harness diagram. It shows two separate flashers, one for the turn signals and the other for the hazard lights. It also includes a wiring color code chart which you should be able to use to determine which is which based on what color wires are connected to each flasher.

Just something simple to check since your problem seems to be connected to the brake lights, there is a switch on top of the brake proportioning valve which is mounted on the frame rail below the master cylinder. Is the wire connector still attached to that switch?

There is also a mechanical brake light switch attached to the brake pedal arm under the dash. Is that connected and functioning?
 

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ShadetreeSeattle

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If all turn lamps light up when the brake pedal is pressed it would indicate to me that the hazard switch is on, which may be half the problem. Ford's wiring for their turn signal and hazard circuit lacked back feed diodes like modern vehicles with combo stop/turn circuits have. Its normal for the brake lamp circuit to back feed into all turn signals when the hazard switch is on with these rigs. Kind of a nussisance when driving with the hazards on. I'd check first if it does it regardless of hazard switch position. It should only do that if the hazard switch is on. If brake activation makes all turn lamps come on regardless of hazard switch position, I'd look into replacing the turn/haz switch. If it only happens when the haz switch is on (like it normally does) I'd look into wiring faults which result in an open 12v line to the flasher modules, (no power at beginning of flasher circuits) and go from there. If I remember correctly the flasher units should always have 12v at one of the two pins and one of them only has 12v with key on. its when they are connected to a lamp load, they begin cycling as they are thermal type flashers, and otherwise the flasher does nothing until a circuit is completed by the turn signal switch or hazard switch. I'm banking my knowledge off the 70's wiring harness but I'm pretty sure it was the same for 60s stuff if it had a column mount turn/hazswitch. Hope this helps.
 

chrlsful

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2X^^^, echo the "grounds" answrs above - its a 50 y/o vehicle (same as mine) after all. Some of the 1st to ck are the 4 straps oem (esp the dash/frame 1). After that the "unit" ones. Nxt start w/a continuity tester for all on that subsystem and even up past the loom to the harness. Last, unless having a good reflective panel or other way to see what results U R getting (white garage door etc) a 1/2 man or boy to yell out "Off"; "On" even w/partial power (dim) has helped me get to the end (not 'bottom') of IT~
8^ )
 

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