Turn signal problem

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Feb 7, 2022 | 03:38 AM

brain360

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Joined: Feb 2022

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Turn signal problem

So I have a 79 f100 and when I have all the lights off on the truck my turn signals and hazards work fine but as soon and I pull the **** to turn in headlights and parking lights my turning signals stop flashing, why?

Feb 7, 2022 | 07:10 AM

TJDentside

Cross-Country

Joined: Sep 2018

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If you’ve got trailer hookups check and make sure someone hasn’t wired your turn signal wires ( green and yellow I think) into the brown wire somewhere.

Feb 7, 2022 | 10:41 AM

Mark8man

Laughing Gas

Joined: Feb 2011

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When did the problem start? Is it all the turn signals or just right or left? Unless someone was doing some creative wiring, I am guessing the turn signals are getting their ground through the headlamp filiments (due to poor grounding elsewhere) and once the HL's are turned on it prevents that from happening.

Feb 8, 2022 | 11:49 AM

meangreen92

Logistics Pro

Joined: Jul 2005

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Those ground wires are two in the front and two in the rear. The front ones both bolt to the radiator support, and the rears are behind the taillights, and bolted to the bed.

Feb 14, 2022 | 11:06 AM

wdon

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Joined: Nov 2011

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Turn signal problem

I had the same problem on my '79 F-100. The main problem (there were also some bad connections, etc.) was that a towing connector was improperly wired to the taillights.

Feb 14, 2022 | 01:57 PM

HoustonDave

Fleet Mechanic

Joined: Sep 2014

Posts: 1,626

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From: NE Texas

(my perennial line) also check that the ground strips inside the socket side are solidly hooked to the ground wires themselves. When that connection goes, you can polish the screwed in ground points forever and still have the symptoms of a bad ground.