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I have an '87 F-250 that has turn signal problems. I turn my turn signal on as if I were to turn left and I notice that my driver's side front turn signal is not flashing but the driver's side rear tail light turn signal flashes just fine. Both turn signals on the passenger side work. I find it a little odd that the rear flashes but not the front. It's not the bulbs because my running lights work, so I'm kind of confused as to where to look first, any thoughts?
 

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The most-likely suspect is the turn/hazard switch. This failure can often be remedied by simply cycling the hazard switch repeatedly. The terminals are designed to self-clean with use.

If that doesn't fix it, the turn switch is likely burned internally. Click this & read the captions:


(phone app link)
 

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The most-likely suspect is the turn/hazard switch. This failure can often be remedied by simply cycling the hazard switch repeatedly. The terminals are designed to self-clean with use.
No it's not other than the wires going directly to the light itself, they're two separate circuits with each having their own flashers and of course separate switches (this isn't a bronco). Self cleaning??
La_Grua00, the first thing to check, which is the problem 99 percent of the time, is a poor ground between the T/S light housing to the body panel.
 

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is the signal/park light double filament bulb?
 

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Unless I'm having a brain-fade which is entirely possible, park light and T/S are two separate filaments. Not so decades ago if I remember right. It's easy to tell, turn on park lights and a turn signal, if the turn signal is way brighter then two filaments.
 

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...the wires going directly to the light itself, they're two separate circuits...
The circuits separate AT the turn/hazard switch. The hazard switch combines them. So if the hazard switch contacts are dirty, some of the circuits don't work, like he's describing.
...and of course separate switches...
No, the turn/hazard switch assembly is for all 4 light circuits, and both flasher circuits.
...this isn't a bronco...
Do you think the turn/hazard wiring is even slightly different? Other than the lengths of the wires?
Self cleaning?
Yes, most switch contacts are designed to self-clean by abrasion. The window & lock switches are notable exceptions.
...a poor ground between the T/S light housing to the body panel.
The turn housing is plastic - it doesn't ground to anything.
is the signal/park light double filament bulb?
Yes. Turn/hazard/brake on the bright filament; park on the dim one.
 

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No, the turn/hazard switch assembly is for all 4 light circuits, and both flasher circuits.
Have you ever even opened the door on a pre '91 (or any) Ford diesel? They have two totally separate switches and two separate flashers. As for the rest, not worth a comment.
 

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Yes - several. Have you ever looked at the wiring diagrams? Are you saying the diesel steering column or turn/hazard switch is different from a gasser's?

No comment about grounding a plastic light housing?
 
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