Fog lights have power, don't work
06-02-2020, 05:02 AM
#1
JK Newbie
Thread Starter
Fog lights have power, don't work
Odd electrical problem. 2011 Stock Wrangler Sport.
Daughter tells me the fog lights don't work. Pull the stick out, lights do not no on and the indicator display does not illuminate.
I remove the bulbs, connect them to a workbench power supply and they work.
I connect a multi-meter to each fog light connector. They receive nominal voltage (13.5V when engine on, 11.8 V when engine off) when the headlights are turned on, even when the fog lights are not on.
I have reset the engine computer (battery disconnect). I also ran a new independent ground for both lights, since I previously had a front turn signal light problem that was fixed by running a new ground and it was easy to tap that.
So what is next? I know the computer does current sensing and turns off if it detects too much current, could that be not right? And why is there nominal voltage when the fog lights are off?
I am a EE so feel free to get technical. But I also really don't care to invest too much time into figuring this out. I might just give up and eventually wire up a separate switch and after-market lights. But the debugger in me wants to figure it out.
On a side note, getting these bulbs to actually insert back into the bumper and stay in is a real pain. I can't quite get the "click" right on either side.
Daughter tells me the fog lights don't work. Pull the stick out, lights do not no on and the indicator display does not illuminate.
I remove the bulbs, connect them to a workbench power supply and they work.
I connect a multi-meter to each fog light connector. They receive nominal voltage (13.5V when engine on, 11.8 V when engine off) when the headlights are turned on, even when the fog lights are not on.
I have reset the engine computer (battery disconnect). I also ran a new independent ground for both lights, since I previously had a front turn signal light problem that was fixed by running a new ground and it was easy to tap that.
So what is next? I know the computer does current sensing and turns off if it detects too much current, could that be not right? And why is there nominal voltage when the fog lights are off?
I am a EE so feel free to get technical. But I also really don't care to invest too much time into figuring this out. I might just give up and eventually wire up a separate switch and after-market lights. But the debugger in me wants to figure it out.
On a side note, getting these bulbs to actually insert back into the bumper and stay in is a real pain. I can't quite get the "click" right on either side.
06-02-2020, 05:10 AM
#2
Super Moderator
It sounds like someone had them wired differently before you got a hold of the vehicle. Maybe they had aftermarket lights and were looking for a steady source of power. For kicks, do they still receive voltage if you flip to the high beam? The fog light harness extends from the passenger side, across the crash bar, and up towards the frame on the driver's side- do you see anything there that's cut?
06-02-2020, 05:22 AM
#3
JK Newbie
Thread Starter
Bulbs are OEM, harness and connector appear to be stock (until I ran separate grounds) and runs exactly as you stated (I have a downloaded electrical diagram and it follows that). No apparent mods to any electrical work under the hood beyond the ground wires I ran.
Fog lights worked for 2.5 years until recently. Then this problem appeared out of nowhere.
Thanks for the tip. Next time I get stuff connected I'll see what happens if I flip the high beams.
Fog lights worked for 2.5 years until recently. Then this problem appeared out of nowhere.
Thanks for the tip. Next time I get stuff connected I'll see what happens if I flip the high beams.