Running lights and dash lights cutting out

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Running lights and dash lights cutting out

Postby Rox Crusher » Mon Sep 01, 2014 10:09 am

Ok, electron whisperers, need some help

I noticed that my dash lights and running lights have started to turn off intermittently.

They come right back on.

Seems like a loose connection but I haven't found anything obvious.

- I installed headlight relay a couple years ago
- I recently swapped old turn signal lights / grill running lights for the older style which doesn't include a ground wire (other style does)
- I also installed and hooked up the horn when I swapped the turn signals

Any and all advice appreciated
1977 Sport, 351w OBDII EFI motor, 4R70W auto, 4:88 gears, ARB lockers, 3.5" suspension, 33" tires.
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Running lights and dash lights cutting out

Postby Colorado75bronc » Mon Sep 01, 2014 11:12 am

Check to make sure the ground points for the turn signal housings are clean. Under dash grounds to be tight and clean. Also it might not hurt to run a ground strap from the body to the frame and frame to engine to make sure you have excellent grounds throughout the truck.

On a side note did you have to reverse the connections on your turn signal conversion? I had to when I did mine because the turn signal was powering the running lights and the running lights were powering the turn signal filament.


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Re: Running lights and dash lights cutting out

Postby Kinder » Mon Sep 01, 2014 12:20 pm

I'm with CO75Bronc on the ground check, the 3 way ground is what we did to TFB's to confirm he didn't have problems and I believe most factory trucks run that setup. Have you looked closely at your headlight switch lately, the dash lights are powered by that silly wound (spring like) wire on the back side of the switch.
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Re: Running lights and dash lights cutting out

Postby Rox Crusher » Mon Sep 01, 2014 12:26 pm

Colorado75bronc wrote:Check to make sure the ground points for the turn signal housings are clean. Under dash grounds to be tight and clean. Also it might not hurt to run a ground strap from the body to the frame and frame to engine to make sure you have excellent grounds throughout the truck.

On a side note did you have to reverse the connections on your turn signal conversion? I had to when I did mine because the turn signal was powering the running lights and the running lights were powering the turn signal filament.


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I have all those grounding wires in place so I think I'm good there.

Which filament is which ?

The turn signal is powering the longer one which is dimmer than the other one.

The shorter / brighter one is powered by the running lights.

Seems the turn signal should be the brightest one ?

If they are reversed, could this be causing the lights to cut out ?
1977 Sport, 351w OBDII EFI motor, 4R70W auto, 4:88 gears, ARB lockers, 3.5" suspension, 33" tires.
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Re: Running lights and dash lights cutting out

Postby Colorado75bronc » Mon Sep 01, 2014 1:33 pm

Turn signal is the brightest so if it is you're good, it wouldn't cause light cutout just the turn signals would be dim and running lights bright, just wanted to make sure. And I agree also with kinder that you should check the headlight switch as that could cause the interior lighting/ cluster lights to cut out. Running lights sound like a poor connection/ ground maybe a fuse box connection too


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Re: Running lights and dash lights cutting out

Postby Rox Crusher » Mon Sep 01, 2014 1:44 pm

Looks like I need to reverse the connections.

I will check grounds again and look at light switch.
1977 Sport, 351w OBDII EFI motor, 4R70W auto, 4:88 gears, ARB lockers, 3.5" suspension, 33" tires.
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Re: Running lights and dash lights cutting out

Postby Viperwolf1 » Mon Sep 01, 2014 1:58 pm

Running lights and dash lights are different circuits. Problem is at the switch.
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Re: Running lights and dash lights cutting out

Postby horseplay » Mon Sep 01, 2014 3:43 pm

I agree with viper replace the light switch and your problem should be gone
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Re: Running lights and dash lights cutting out

Postby Gregg » Mon Sep 01, 2014 7:53 pm

Have you been to the optometrist ? That's the doctor that checks your eyes...not your a$$. Your Bronco is fine.
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Re: Running lights and dash lights cutting out

Postby Rox Crusher » Sat Sep 06, 2014 5:13 pm

Replaced the light switch this afternoon. That is tricky getting the little adapter and the light switch behind the dash to line up with the socket so you can thread in the retaining nut from the front.

Also switched the wiring on the new turn signals so they were correct.

Thanks for the tech support guys !
1977 Sport, 351w OBDII EFI motor, 4R70W auto, 4:88 gears, ARB lockers, 3.5" suspension, 33" tires.
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Re: Running lights and dash lights cutting out

Postby Colorado75bronc » Sun Sep 07, 2014 9:15 am

Awesome! Glad to hear it's fixed


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Re: Running lights and dash lights cutting out

Postby Rox Crusher » Sun Sep 07, 2014 9:50 am

I drove home from docono last night and it didn't mess a beat.

I might be imagining things because I don't drive it at night much, but it seemed like the dash lights were a little brighter than normal which is good
1977 Sport, 351w OBDII EFI motor, 4R70W auto, 4:88 gears, ARB lockers, 3.5" suspension, 33" tires.
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Re: Running lights and dash lights cutting out

Postby horseplay » Sun Sep 07, 2014 2:12 pm

Makes sense less resistance better currant flow better potential.
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Re: Running lights and dash lights cutting out

Postby Moab Mike » Sun Sep 07, 2014 4:02 pm

Rox Crusher wrote:I drove home from docono last night and it didn't mess a beat.

I might be imagining things because I don't drive it at night much, but it seemed like the dash lights were a little brighter than normal which is good


A new rheostat (dimmer) in the new switch would account for that.
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