Alright, I am reaching my witts end, I have a 2013 Roush S3 that I cannot get the low beam headlights to shut off.

I have tested the in-car wiring to match the test guide from Ford with no issues. I have replaced the Headlight Switch, I have grounded pin 6 directly, replaced the Smart Junction Box in the car, and I have now replaced the headlights with brand new Ford Headlights (They were OEM before as well). No matter what the Low Beams just will not shut off unless I pull the headlight fuses.
I have tried using a Snap-On Modus and I can control everything but the low beams.

I am running out of ideas, to be honest, and I am not sure what to think and I was hoping the forums might lend me a hand.

What am I missing here?

 

Did you try disconnecting the battery to try and reset them and are they factory or aftermarket?

 

I have a Roush Stage 2, but the RS3 is the same as the RS2 and any other GT Mustang as far as the headlights go. Sounds like maybe a short or other modification to the headlights or fog lights that by-passes the switch?

 

Yes the only way to shut them off is to pull the fuses and they are factory and as of tonight brand new factory because I thought the others might have an issue internally.

 

I sadly have not made any changes to the fog light or headlight wiring. It should all be OEM as the only aftermarket thing was an old alarm and I removed that as well thinking it died.

Even when you command them off with the Modus they just won't shut off. I have to say it's rather frustrating. I checked the harness under the radiator cover still couldn't see anything and I've pulled the headlights out and checked I didn't see any issues there either.

 

This going to sound dumb but are they in auto, also are they HID bulbs. And can't remember but did you try checking the switch if they are in auto maybe the switch for them is going bad.

 

I have treated the switch and have a replacement switch here just for good measure.
In or out of auto they won't shut off, if you remove the switch and ground pin 6 it's supposed to tell the SJB to turn them off and even that doesn't work, all the other lights will turn off but the low beams just won't shut off.

 

Did you use relays for them if they are HID bulbs

 

Factory HIDs, I've checked for relays in the SJB and Main fuse box, there's only fuses.

 

Did you try checking the SJB itself. Check the connectors and see if they have any corrosion on them. My mustang is a 07 but just going through the possible options. Everything I have been seeing has this on there. You probably checked them, I just had to ask.

 

Yes, I even replaced it still no change

 

Wow, I am at a loss here. Sounds like you have checked or replaced just about everything. So no matter where the switch is Auto or manual or off the headlights (HIDs) remain on. It sounds like some how the switch is being by-passed. If this was only when in auto mode it could be the sensor is not acting correctly and sensing no light. But since it is only with pulled fuse they go off, then some how it is as if they are direct wired. All stock and no mods. Must be some kind of computer issue. Is that the ECU?

 

That is what I would be leaning towards. I am at a loss my self. Are any of the harnesses or connection hot when they stay on after the car is off.

 

So I wanted to update on some more testing I did because I decided to go through and try again as well as I also got access to OASIS.

So Testing again in the car cabin resulted in everything working and testing correctly. Even pulling the Headlight Fuses in the car showed no change in the Low Beams shutting off, only pulling the fuses in the Engine Bay shut them off.

Next, I started testing in the engine bay and ended up testing Pin 1 on the Drivers Side as it was easier to access and I found that using the Ford Procedures I did have Voltage with the switch on and the voltage dropped to 0 with it off. Showing that the switch is getting all the way to the front. But again as soon as I plugged the headlight harness back in the low beam was on even though it showed no voltage going to Pin 1. That means that this is not the wiring. (I even ohm tested the grounds on that headlight to confirm they work and they were connected and working) which leads me to one other possible conclusion even though it seems quite unlikely... the Ballasts themselves are the issue. For some reason, they are locked on.

I am going to try replacing the ballasts now and see what happens.

 

Very strange. Good luck and hope you figure this one out.

 

Replaced the Ballasts with OEM and the lights work just fine... not the problem I expected but good to know for anyone else who has this problem.

 

Wow, glad you figured it out. So the ballasts would act like a capacitor and hold a charge? Or did they have some kind of a short that would not go off without killing the battery or pulling a fuse?