Headlights Won't Turn Off - Fried Switch???

[Hodor]

I was beginning my Roush boost gauge install and pulled the headlight/dimmer switch panel out to expose the wires and connectors on the back of it. From reading various posts, many people seem to tap into those wires to power their gauges, so I was trying to figure out which wire had go where to get the proper lighting (white during day, blue at night, etc). I was touching the ends of the gauge wires to the back of the connector pins before splicing into any wires and making sure I had the correct colors coming on as I wanted. Just as I was figured out which wires needed to go where, I noticed that the headlights would not shut off now, no matter what I did. I even unplugged the headlight switch and removed it and the headlights were still stuck on. I had to unhook the battery to get the lights to turn off...

Did I somehow fry the headlight switch? I don't know much about automotive wiring - how can the headlights be stuck in the ON position when I even removed the switch??? Do you think I fried the headlight switch and need a new one, or could I have done something else??? Any help is appreciated, thanks...

 

[Beernuts]

The headlights will remain on if the smart junction box does not detect a signal from the headlight switch (ie: disconnected.) The headlights will also remain on if the SJB detects multiple signals from the headlight switch (ie: fried switch or wiring.) Note: this is a safety feature so you don't lose your headlights should the switch or wiring fail.

Have you reconnected the headlight switch after removing/replacing the battery cable and verified the lights stay on?

If so, with the switch disconnected, try grounding pin 6 of the headlamp sw connector (vehicle harness side) and see if the headlamps turn off. If they do, your switch is likely the culprit.

 

[Hodor]

Yes, they stay on after reconnecting the switch and the battery.

Looking at the wiring schematic of the harness, I see that pin #6 is the "Headlamp Off" wire, so it makes sense why you suggest doing this. Thanks for taking the time to help me out and explain things for me, I appreciate it! I'll give that a try when I get home from work.

Where in MI are you? Thanks again.

 

[Beernuts]

No problem. There is some additional troubleshooting we can do if you have a multimeter. I'm in Livonia, you?

 

[Hodor]

Grand Rapids

 

[Hodor]

Yep, the lights turn off when I ground pin #6 and I can turn the fogs on with another - almost certain it's the switch. Ordered a new one. Thank you!

 

[Beernuts]

Good to hear, now dont fry the new one!

And dont feel bad, apparently this happens enough that Ford has issued a service message:

SSM 12019 - Low Current Switch Failures Due To Improperly Installed Accessories
Some 2012-2013 Multiple vehicle lines equipped with aftermarket or Genuine Ford Accessories (GFA), may experience failed low current switches such as a headlight switch, due to high current inputs/draws. These switches are designed to toggle low current reference voltage and will fail if current exceeds the switches design intent. If a low current switch has failed due to an over current condition, inspect for improperly installed aftermarket or GFA accessories. Improperly installed accessories can directly affect switch function. Please review the Warranty and Policy manual for proper repair coverage.

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