Turn signal problem
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Turn signal problem
06 F150 FX4 crew cab. Got a fast flash with left turn signal. Front signal and mirror works properly. All other lights work as they should. Left rear not working. Started replacing parts, bulb, socket, pigtail still not working. Ohm meter shows 0 just like the right side. After replacing socket and pigtail it blinks 2-3 times then quits. Replaced flasher nothing. Decided to bite the bullet and replace multifunction/turn signal switch. 2-3 regular blinks then quits. Obviously I am not very good with electrical issues. Any ideas appreciated.
Fleet Mechanic
Joined: Apr 2016
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You have an open circuit in the left rear . You need to see where you are losing 12vdc signal or good ground for light . Fast flash means it sees a lack of current draw on that circuit. use a long lead to battery for reference . You can even use it to supply ground to that side . Forget the ohmmeter unless you are very electrical minded . A 12vdc test light will be better . It draws load . You have a connector under drivers side that gets crudded up ,clean it with contact cleaner ..
Your reference lead from battery can be either positive or negative . You may want to use a inline fuse at battery if you go to use a positive reference. That way if you make a mistake fuse will blow . It can make your head spin if you aren't an electrical guy .I have friends who I forbid them from doing electrical work since they just can't think electrical . I do it for free for those folks .
Your reference lead from battery can be either positive or negative . You may want to use a inline fuse at battery if you go to use a positive reference. That way if you make a mistake fuse will blow . It can make your head spin if you aren't an electrical guy .I have friends who I forbid them from doing electrical work since they just can't think electrical . I do it for free for those folks .
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The head is spinning already. I plan to get with a friend that has a better grasp of electrical next week and share the info you gave. I did check the connectors under the drivers side. they were dirty but seemed well connected. I opened and cleaned them with no change. Beside one of the connectors is a green wire sticking out that capped with rubber. It comes from the harness coming down from the cab. I assumed (yea I know) it was for some option not used. Again any time you completely disconnect and reconnect you will get 2-4 blinks then nothing. Thanks for replying.
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If your other rear lights work, your ground is fine. All rear lighting share a main ground that is located above the spare tire. Each tail light shares a ground with that turn signal.
Hyper flash indicates an open circuit in the left turn signal. Since the left tail works (at normal brightness?) you know the ground is good, therefore, it can only be in the power... I don't have a schematic in front of me, but I say with 90% certainly, that the left turn power wire is orange with a light blue stripe.
Unplug the plug that feeds the rear lights. Hook one end of your test light to ground, with the turn signal on, check the truck side harness at the or/lb wire. If the light flashes, remove and repair/replace the rear harness. If not, remove the trim panels along side the driver's side seats, search in that bundle for the appropriate wire and try to find the break. It's common to break about the middle of the driver's front door... it's possible to be elsewhere, but these would be the most common causes...
Hyper flash indicates an open circuit in the left turn signal. Since the left tail works (at normal brightness?) you know the ground is good, therefore, it can only be in the power... I don't have a schematic in front of me, but I say with 90% certainly, that the left turn power wire is orange with a light blue stripe.
Unplug the plug that feeds the rear lights. Hook one end of your test light to ground, with the turn signal on, check the truck side harness at the or/lb wire. If the light flashes, remove and repair/replace the rear harness. If not, remove the trim panels along side the driver's side seats, search in that bundle for the appropriate wire and try to find the break. It's common to break about the middle of the driver's front door... it's possible to be elsewhere, but these would be the most common causes...
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heres a partial schematic, left lt green /org.
when you say it quits after 2-4 flashes --does it stay lit or go dark , if its going dark .the load is breaking down a connection along the way, it could be the ground side going to that junction or a wire is broken inside insulation and barely making contact, corrosion can do that . you can find it doing a voltage drop test when its failed. take that common blk wire on left rear bulb and run a express line to battery negative . that will tell you if its s grd problem . I'm not there so i would be observing more ,its just hard to see it from this distance .
doing this test it would be prudent to have running lights on and observe left rear ,does running left stay good ? if so ground is okay .What happens if you hit brake .
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heres a partial schematic, left lt green /org.
when you say it quits after 2-4 flashes --does it stay lit or go dark , if its going dark .the load is breaking down a connection along the way, it could be the ground side going to that junction or a wire is broken inside insulation and barely making contact, corrosion can do that . you can find it doing a voltage drop test when its failed. take that common blk wire on left rear bulb and run a express line to battery negative . that will tell you if its s grd problem . I'm not there so i would be observing more ,its just hard to see it from this distance .
doing this test it would be prudent to have running lights on and observe left rear ,does running left stay good ? if so ground is okay .What happens if you hit brake .
You mention the ground again... With the symptoms described, it is highly unlikely to be a failed ground, even between the light housing and splice 401. A failed ground in that location, with the headlights off, would most likely cause the current to flow through the turn/stop filament, then on it's search for ground it would go through the left tail filament, back through the brown wire to the RIGHT tail filament, and finally to ground. Since this essentially puts all 3 filaments in series, the flasher would have enough resistance to flash at the normal speed, but all 3 filaments would illuminate very dim (if at all).
A failed ground at G300 would cause all the rear lights to be inoperative, or operate very dim.
Your schematic doesn't show it, but there *is* a ground for the rear lighting above the spare tire.
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