Rapid Turn Signal

[MasterEngineer]

Hi all,

I've been looking through the forum however not sure if there's a single clear/concise answer to my question...

Left turn signal blinks rapidly, and I know it's the rear signal (as it's the one that doesn't blink). However, I always thought that a rapid turn signal was simply a burned out bulb - but as I'm sure you're all aware, there's a single bulb in the taillight housing (not counting reverse light...), and it works normally with the brake lights, running lights, and hazard lights.

If anyone could provide a list of troubleshooting steps, it would be greatly appreciated.

Thanks in advance!

 

[MR. EDDIE]

First of all what year & model are you working with.

In the past with some of my older vehicles I replaced the bulbs with led bulbs and that caused a rapid blinking scenario. Check all your bulbs (I know its a pain in the rear) but at least you can be certain that its the proper bulb in its place. Also if you have mirrors with turn signals check that those are working as well.

 

[1955moose]

I agree with Mr Eddie, you've probably got a burnt out bulb. That said, check to be sure you don't have a different bulb on the left side, from right. Make sure all connections are clean, I put a little die electric grease on terminal ends. It's most likely a burnt out bulb or connection. Take your time, you'll find your problem. Post your results.


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[MasterEngineer]

Hi guys,

Sorry - the vehicle is a 2003 Expedition EB 4X4 5.4L.

It only has a single bulb in the taillight, which lights up at the "dim" level for running lights, and then goes to full brightness when the brakes are applied. The front left turn signal in the headlamp assembly illuminates, and the turn signal in the side mirror also illuminates when I use my left turn signal (they both blink rapidly), however the bulb in the taillight assembly does not illuminate at all whatsoever (when I just use the left turn signal).

When I use my hazards (four-way flashers) or step on the brakes, the left taillight lights up just fine, including the hazards blink at the normal rate.

Given that information, do you think the short exists in the wiring/bulb socket/taillight assembly, or is it something else?

 

[1955moose]

Sounds like a wire/ connection problem. Try wiggling the wires up to the socket. You also have to see if you have power to the bulb. If memory serves, I believe you have a separate fuse for left and right turn signal. As we alway state, not only check for blown fuse, but also for 12 volts at both sides of fuse with turn signal activated. I have a 2000 expedition owners book, in mine it shows number 20 fuse in the under hood box is for trailer tow stop and left turn lamp. Let us know what you find.


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[MasterEngineer]

Okay, I'll check the connections and voltage across the fuse.

And I'm just trying to check my understanding (not argue lol), but in theory, if the left turn signal's fuse is blown/inoperative, then none of vehicle's left turn signals should operate, right? Or can a faulty fuse screw with a single lamp?

 

[1955moose]

No your right, they should be powered by same fuse. Check power at socket, I'm betting if your fronts flashing ok, you've probably got corrosion or problem with wire. Moisture gets into lenses and causes connection problems. If you have a schematic for the turn signal circuit. You could trace all the way back to power, and diagnose from there. I'm betting your bulb flashing fast is a simple problem, most things are, after we do a bunch of diagnostics. Has been for me over the years.


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[MasterEngineer]

Okay, not sure if the problem changed or I'm just an idiot and missed this, but before I changed the bulb I checked the brake lights, and noticed that the taillight in question did not light up. Voila! The second filament must've burned out, so $7 at the auto parts store and 5 minutes with a screwdriver and the turn signal now operates as it should.

Thank you all for your help and contributions, and sorry to have bothered you with such a trivial task.

 

[1955moose]

Told you it would be simple! Glad you figured it out Moose.


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