Hello all. I'm in need of some assistance concerning a single low beam issue. Both high beams work. The right low beam does but the left does not. I've tried a new lamp and verified the left low fuse is good.
Tomorrow I'll use a voltmeter to check the voltage at the lamp plug but was wanting to know what voltage I should be expecting normally. Also if anyone had any ideas other than a possible failed wire and if a bad light switch would cause only one low beam current failure.
Thank you for any knowledge you can supply.

Kevin

 

Some more info. Checked the voltage on the lights. My left side headlight low beam voltage is at 8.89 and stays at that level. The right side shows 12.3 unless the high beams are on then it drops to the 8.89. It appears to me the left side is not switching like it's suppose to be. I've been trying to find the headlight relay but have no idea where it's located in this model. Google search is only showing pre 2007 model info.

 

Isn't there a wiring or fuse/relay diagram in the manual? Mine is not handy right now.

-- Chuck

 

Did you figure out what the problem was? I have the exact same issue as you. The only difference is that I read 8.45v on the low beam. Also, my daytime running light does not work on that side too. Everything else checks out ok. Fuses are good.

Any help appreciated!

 

I took it back where I bought it from, Pre-owned. They troubleshot it for half a day and had tentatively determined it was in the fusebox. I got the impression that 8.XX voltage isn't suppose to be there at all when the low beams are not active but it is. They tried to find out where it could be coming from and it points to something in the fusebox. They were going to see what info they could get from the Ford place but as yet I haven't an answer. I'm not happy with the dealership I bought it from so I'm still investigating it on my own. I'll post if I find out a definite cause and or a solution.

Also, it is definitely not the switch, they swapped that out.

Does the 2008 Xpy have a LOM. A Lamp Out Module? Reading online, this would cause it if the 2008 has it. The manual has no info on it and no fuse labeled as such.

 

Yeah, from what I understand so far, that low voltage is supposed to be there. The same voltage (8.45-8.89v) is on the working side low beams when I switch it to high beams. So there is always voltage at the low beams. But on the working side, when it is switched back to low beams, it obviously switches to 12v. The non-working side stays at 8.45. I just got my FORD Super Duty repair manual, and it has some awesome diagnostic stuff in it. Hopefully I will get to do some diagnostics in the next couple of days and I will come up with the solution.

I don't think the 2008 has a LOM. Mine is a 2009 F-350, but they work the same. I don't think they are used anymore.

I will post the solution here if you don't get to do it first. I think between the 2 of us we should be able to get it done. Although from what you told me of your dealer, they don't sound too competent with the Ford electronics. I would probably have it figured out tonight, except I am not sure if I have the time. Good luck and keep me posted!

 

That's interesting. I also had the 8.xx voltage on the low beam of the working light that did switch to 12 volts when lit. Sounds like we have the exact same problem albeit on different models but the basic electronics should be the same. As far as my dealer, that's an understatement. I look forward to what you come up with and good luck for both of us..

 

Ok, I finally had a bit of time to test. I ran out during my lunch and pulled my headlight out and tested. To make a long story short, it is a bad ground. From what I have been reading, this is a common problem. I did all of the diagnostics from the Ford repair manuals I have (dealer manuals are extremely thourough! 8-P) and everything checked out until I was doing the ground testing. You are supposed to have a minimum of 10,000ohms an I had 0. I did a quick ground test on the high beam and I set the meter to 20k and got 20k ohms. So now I have have to go through the laborious task of finding the bad ground. The manual I have has all the wiring diagrams too, so that will help. Have you fixed yours yet? If you need an explanation of how and what to test, let me know, but I think I would definitely start with the ground after all of the easy stuff is done. (fuses, etc....) Let me know!

 

No not yet. Between work and my daughter's upcoming graduation I haven't had time. Saturday afternoon I plan on pulling the light and checking the ohms on the ground. The fuses and light switch are all good.

 

Ok, there is a specific way you need to check the ground. You need to unplug a specific wire set from the SBJ. Then check the ohms from your low beam wire to ground. I hope yours is the same as mine. I am going to try to get the specific diagnostic pages for that circuit and send it to you. I will let you know tomorrow. I have a busy day with the kids too, BD party, swimming lessons.... I know how it is!

 

Sorry it took me so long. Been crazy busy! I got the diagnostic pages you need out of the manual I have. I hope they are the same. I think they probably are. PM me your email and I will send it to you. Its only 317kb so its pretty small. This is Ford's step by step diagnostics for their techs, and very detailed. It will pinpoint your problem so that you know exactly what to fix.

 

no option to send a pm. left you a visitor message on your profile.

 

No problem! I have sent you the diagnostic steps. If you have any questions, don't forget to post them here so that everyone else can benefit, and if you do figure out your problem, please post also. I am eager to hear if your ground is bad the same as mine.

 

Hey mate, nothing has come through yet on my email.

 

Sorry about that...check again.....