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Headlights go out when using turn signal


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MarineGrunt
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Feb 17, 2013, 8:21 AM

Post #1 of 14 (3776 views)
Headlights go out when using turn signal Sign In

My uncle has a 1999 Mercury Grand Marquis 4.6. It has 171k. Whenever you use the left turn signal the headlights go out. It seems like it would be turn signal lever since it also controls the high beams but it's just a guess. Have you guys ever heard of this happening? Any ideas on how to troubleshoot would be appreciated.

Thanks!


Sidom
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Feb 17, 2013, 12:16 PM

Post #2 of 14 (3743 views)
Re: Headlights go out when using turn signal Sign In

Can you get the high beams to come on when the turn signal is on?....

I'll try to pull up the specs on this one.......You may want to double check that is has the correct headlights....I believe this one use a module for the lights and if the wrong bulbs are in there the module can shut the headlights off cuz it thinks there is a short......


MarineGrunt
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Feb 17, 2013, 1:45 PM

Post #3 of 14 (3730 views)
Re: Headlights go out when using turn signal Sign In

Thanks Sidom. I don't currently have the car to test anything but will try and get it soon. I just didn't know if it was some known problem with a definite fix. I'll give my uncle a call and see if he replaced the bulbs right before this started happening. Hopefully I'll be able to get the car here in a few days and start some troubleshooting. I just have no idea where to start. I'm not that good at troubleshooting, and especially when it comes to vehicle's electrical system, so will definitely need some direction.


Sidom
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Feb 17, 2013, 1:52 PM

Post #4 of 14 (3727 views)
Re: Headlights go out when using turn signal Sign In

Not a problem.....My base is down right now so I haven't been able to check the system yet.....You've done pretty decent with the other stuff so this shouldn't be a problem...At some point though you may need a scan tool to access the module.....My memory sux....I know you have the stuff to get alot things done but don't recall what type of electrical stuff you have....

You may be right though & have a bad multi-function switch......Those are common to go bad & a lot stuff does go thru them...


Hammer Time
Ultimate Carjunky / Moderator
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Feb 17, 2013, 2:17 PM

Post #5 of 14 (3722 views)
Re: Headlights go out when using turn signal Sign In








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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



nickwarner
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Feb 17, 2013, 8:51 PM

Post #6 of 14 (3704 views)
Re: Headlights go out when using turn signal Sign In

I hope Way2Old pops in on this one. This is the same basic design as the cop car fleet he works on. Chances are he knows an exact culprit off memory alone.


Tom Greenleaf
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Feb 17, 2013, 9:08 PM

Post #7 of 14 (3702 views)
Re: Headlights go out when using turn signal Sign In

You are right Nick. He would know this instantly no doubt. I've been thinking and can't figure why one side would behave like that and not both?

My best would be if it has cornering lamps that are separate (not sure for this year) that perhaps it's involved otherwise I'm lost. I'd be chasing a ground shared but that doesn't make sense to me for just one side either? Tom


MarineGrunt
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Feb 17, 2013, 9:12 PM

Post #8 of 14 (3699 views)
Re: Headlights go out when using turn signal Sign In

Sidom.....all I have is a basic scanner (Innova 3160b). Other than that just multi meters and test lights. I haven't really messed with much when it comes to the electrical system on vehicles other than stereos and a car starter. I do understand the basics of wiring so should be okay as long as I'm nudged in the right direction.

Thanks for schematics HT.

Nick...Sounds like Way2Old might have some good info too. By the way. Thanks for the info you left the other night about that guy's videos. You were right. Was out to eat with the wife. I haven't even called the guy that I work with back about his truck. He went from questions about his truck to questions about his dad's Taurus. The car had codes Bank 1 and 2 lean but for some reason though he should scan it again so kept bugging me about driving 45 minutes to scan it and help out. He said the battery wouldn't hold a charge. I kept telling him the first thing he needs to do is get a new battery but said he didn't want to get a new battery until he knew what was wrong with it. Told him it was kind of hard to troubleshoot if the battery is dead so to take care of that first. He kept calling with questions. I asked him about the battery and they still hadn't replaced it. He also said it had dry rotted vacuum lines but didn't want to replace those either until they "figured out the problem" and wanted to scan it first thinking it was going to tell them it had a bad vacuum line or something. I'm done! I don't know you guys deal with these type of idiots everyday! I'd be in jail for assault once a week.


Hammer Time
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Feb 18, 2013, 4:15 AM

Post #9 of 14 (3685 views)
Re: Headlights go out when using turn signal Sign In

As you can see in the diagram, there is nothing in the headlamp circuit that isolates one light so your problem has to be in the local wiring somewhere.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



MarineGrunt
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Feb 18, 2013, 10:04 AM

Post #10 of 14 (3672 views)
Re: Headlights go out when using turn signal Sign In

Thanks HT. This is where I'm out of my comfort zone. What are the chances it's in the multi function switch? If you don't mind can you explain to me what your first steps would be to try and find the problem? As Sidom recommended, I know I need to find out if the bulbs have recently been replaced first.

My uncle isn't going to take the car to a shop because he doesn't think it's worth throwing a bunch of money at it. I figure this could be a good learning experience for me. I'd really like to learn more about testing a vehicle's electrical but have no idea where to start. If you think it's out of my league I understand.


Hammer Time
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Feb 18, 2013, 12:36 PM

Post #11 of 14 (3669 views)
Re: Headlights go out when using turn signal Sign In

You said that you are losing one headlight. There is a single wire feeding both lights and splitting so find out where that circuit is dropping out. Don't forget to look at grounds too.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Tom Greenleaf
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Feb 18, 2013, 1:21 PM

Post #12 of 14 (3664 views)
Re: Headlights go out when using turn signal Sign In

I understand this the both headlights quit when left directional is used? Am I mistaken? -- T


Hammer Time
Ultimate Carjunky / Moderator
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Feb 18, 2013, 1:25 PM

Post #13 of 14 (3660 views)
Re: Headlights go out when using turn signal Sign In

Apparently you're right. In misread that.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Tom Greenleaf
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Feb 18, 2013, 2:09 PM

Post #14 of 14 (3657 views)
Re: Headlights go out when using turn signal Sign In

OK - Here's a wild arse guess for a place to look and no I haven't studied one in person yet. Pic please......

Note the cornering lamp. This appears integrated with the assy of the whole thing but bet it is exposed to substantial moisture and possible spray off the wheel. It should only come on when headlights are on and can't be sure of that. It may have a separate hole thru where the assy all goes in but should have separate wires to it. Just a hunch worth checking that early in the hunt as a problem spot tripping whatever fail safe for headlights are in this car.

In the past when those screwed up they could be a mess or dirt but usually they just didn't work alone and you just fixed that frequently just a bulb or corroded socket. Just a wild guess for a place to inspect early in this game -- Tom






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