# Brake and signal light out - troubleshooting questions



## NancyNGA (Jan 12, 2017)

1997 Ford F-150

Last summer: LEFT rear signal light went out.  Magically it started working two days later and has worked ever since.

This week: both the signal and brake lights went out on the RIGHT rear.

Could the two incidents related?  Too much of a coincidence to just be two bad bulbs? 

It is rather difficult to replace the bulbs.   Not sure it's worth the effort to do it myself, especially if that's not what's wrong.

 Can anyone suggest any tests I can do to narrow the problem down some?


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## Don M. (Jan 12, 2017)

Intermittent bulbs are usually a sign of corrosion in the lamp socket...especially on vehicles over 10 years old in a fairly humid climate.  There really isn't any "quick fix" for this...other than taking the bulbs out, and cleaning the bulb socket contacts with a small piece of Scotchbrite, etc.  I had similar problems a couple of years ago on my old 1997 Dodge Dakota, and I took the bulbs out, rubbed the contacts with Scotchbrite, then sprayed the sockets with a burst of WD-40, wiped of the excess with a q-tip, and then cleaned the base/contacts on the bulbs before reinstalling....no more troubles, since.


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## NancyNGA (Jan 12, 2017)

Thanks, Don!  That makes sense.  Gonna get my wrench out and give it a try tomorrow. Tonight I need to hunt for the wrench.  :lol:


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## steelcitiesgray (Jan 12, 2017)

Nancy, Also check Youtube for video of replacing bulb for your make car. Sometimes there are short cuts, like going through the trunk to replace bulbs.


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## NancyNGA (Jan 12, 2017)

Found the wrench and got the RIGHT rear cover off.  Easier than I thought.  There are 3 bulbs.  Took them all out and cleaned them and Wd40 spray.  They looked fine.  Couldn't see any corrosion in sockets or on bulbs.  

Running lights are OK (top and bottom bulb), but still no signal, brake or backup lights on RIGHT rear.  I don't think the center light over the cab is working either, but it's difficult to tell. I even forgot what that's for.  Brake?   I've rigged up a mirror with a piece of tin roofing.  Ha!  

Everything is working fine on the LEFT side, and on FRONT RIGHT.

 I guess there are two intensities of light on the two bulbs.  Don't know enough about it.  Will go off and study more before asking anymore silly questions.   Thanks!


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## GeorgiaXplant (Jan 12, 2017)

Could it just be a fuse? And you're not asking silly questions!


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## steelcitiesgray (Jan 12, 2017)

GeorgiaXplant said:


> Could it just be a fuse? And you're not asking silly questions!



Fuse was my thought too.


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## NancyNGA (Jan 12, 2017)

But would there be TWO fuses---one for the LEFT and RIGHT sides?   The LEFT side is working fine.   Still Googling.


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## GeorgiaXplant (Jan 12, 2017)

Google is my best friend


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## Butterfly (Jan 12, 2017)

I had a similar problem with my old Saturn.  I took it up to  Pep Boys and they fixed it right up, cheap!  I HATE dealing with that kind of stuff, just frustrates me to the point of wanting to scream.


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## Don M. (Jan 12, 2017)

If you didn't find any issues at the bulb/socket, and it is only the right rear that is failing, that is a pretty good indicator of a wiring problem....the wiring harness to that housing may have come loose or been damaged.  If you have a multimeter, you can verify if the lamps/sockets are getting any voltage...if not, I would suspect a wiring problem.  You would almost need to have a repair manual for a particular vehicle to trace any kind of wiring problem.  If the other lights are working properly, it should not be a fuse...generally a bad fuse would cause All the lights to fail.  In such a case, unless you are a fairly good troubleshooter, you would probably be better off taking the truck to a shop, and they can probably find the problem easily, and hopefully not overcharge you.  Here are a couple of sites where you might be able to get a wiring diagram for your truck....but unless you have done something like this before, it can be a real "learning experience".

http://www.productmanualguide.com/newpdf/1997-ford-f150-wiring-diagram.pdf

http://www.autolib.diakom.ru/CAR/Ford/1997/Pickup F150/SYSTEM WIRING DIAGRAMS/


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## NancyNGA (Jan 12, 2017)

Don M. said:


> If ....it is only the right rear that is failing, that is a pretty good indicator of a wiring problem....the wiring harness to that housing may have come loose or been damaged. ...



That's what I was thinking.  I'll take a look at those bulbs again tomorrow in daylight.  There must be 2 filaments in two one of them, meaning 2 wires going to each bulb.  Maybe I'll check for a loose or broken wire as far as I can follow it. 

Could be there are two things going on at once.

 Thanks for the links, Don. I'll bookmark them. No doubt above my pay grade.   I'll probably end up taking it to Pep Boys, or the like, but I want to know if what they tell me when I go there makes sense.

Just hope it's not some electronic device, the kind they probably quit making for this model, or cost hundreds to replace because they have to take out the whole dashboard,... etc.... 

Thanks again.


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## Don M. (Jan 12, 2017)

At the Bare Minimum....replace, or swap the bulbs with the working side.  You can meter the bulbs, to verify that the filaments are good, but replacing the bulbs would be the best "test".  It would be a shame to pay a shop $50+ to replace a couple of $2 bulbs.  Being a 1997 model, I doubt that there is anything in the "electronics" that would cause such a problem....that kind of thing only happens on some of these newer vehicles.


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## NancyNGA (Jan 13, 2017)

Update:

Switched all 3 light bulbs to the other side this morning.  The signal light didn't work over there either. [_Now,_ I can see the broken filament. ]  But the other two bulbs *did* work.

Decided to just replace all 6 bulbs because the old ones are original, and will be 21 years old this spring.  Now everything is working. Still doesn't quite make sense, so I don't feel like celebrating, just yet. We'll see...

Oh, yes!  The brake light at the top  of the back of the cab is not working. I forgot about it.  But that's a job for another day.

Thanks everyone.  I learned a lot!


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## Ken N Tx (Jan 14, 2017)

NancyNGA said:


> Update:
> 
> Switched all 3 light bulbs to the other side this morning.  The signal light didn't work over there either. [_Now,_ I can see the broken filament. ]  But the other two bulbs *did* work.
> 
> ...



The light in the back roof middle on my truck is a bed light that works when the door is open.

Bulbs come 2 in a pack, best to replace both sides..


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## NancyNGA (Jan 14, 2017)

Ken, mine looks like this.  The two white lights are bed lights.  They are both working.  The middle one is a brake light. It's out.  I'll get to it eventually.   Looks easy enough.  Just 2 screws.  Famous last words....


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