Headlights come on in Parking Light position

[Tjhoward84]

Anyone have this happen? After replacing the blubs in my fog lights, fuse 27 (5A) blew which controls the fog light relay. Replaced the fuse and now the fog lights no longer work and the headlights come on in the Parking Light position. Replaced the headlight switch assembly inside the cab of truck and still the same issue. Any advise would be great.

 

[Tjhoward84]

OK, one problem fixed. Fog lights are working now. The fuse (27 - 5A) under the dash is only to trip the fog light relay under the hood. That was blown (I knew that). There is another fuse in the main fuse box under the hood that runs the fog lights. It's fuse 9 (15A), it too was blown. Replaced that and the fog lights work. Now to fix why the headlights are coming on when the headlight switch is in the Parking Light position.

 

[Yupster Dog]

OK, one problem fixed. Fog lights are working now. The fuse (27 - 5A) under the dash is only to trip the fog light relay under the hood. That was blown (I knew that). There is another fuse in the main fuse box under the hood that runs the fog lights. It's fuse 9 (15A), it too was blown. Replaced that and the fog lights work. Now to fix why the headlights are coming on when the headlight switch is in the Parking Light position.

You would get more help if you started your own thread instead of at the end of multiple dead threads. But good job on trying to look up your problem first.

look at fuse 3 under hood (Main Light Switch, Headlamp Relay, Multifunction Switch) you didn't mention that one.
If that fuse good more than likely you fried you switch.

FYI in the future always good idea to disconnect battery when working on electrical. And never with switch on.
I mean you wouldn't work on your transfer case going down the road would you?

 

[Tjhoward84]

Update number 2 - everything works as it should once I reversed the fog light mod. Removing the jumper wire between the brown and white/black wire solves the problem of the headlights coming on when the headlight switch is in the Parking Light position. What's weird is this jumper and the mod have been on the truck since 2006. I'm sure I mess up the headlight relay when I hot swapped the fog light bulbs.

I checked all fuses under the hood (including fuse 3) and the fuses under the dash and they are appear to be good. Not sure how to check the relays.

 

[99WhiteC5Coupe]

Update number 2 - everything works as it should once I reversed the fog light mod. Removing the jumper wire between the brown and white/black wire solves the problem of the headlights coming on when the headlight switch is in the Parking Light position. What's weird is this jumper and the mod have been on the truck since 2006. I'm sure I mess up the headlight relay when I hot swapped the fog light bulbs.

I checked all fuses under the hood (including fuse 3) and the fuses under the dash and they are appear to be good. Not sure how to check the relays.

Your first post did not report the modified wiring in the fog lights - that may have helped others on this forum with their advice.

 

[Tjhoward84]

Your first post did not report the modified wiring in the fog lights - that may have helped others on this forum with their advice.

I deliberately did not mention the fog light mod since it had been working flawlessly since 2006. I didn't want people to instantly jump to that being the issue. It's worked for 14 years. Obviously there is something that happened when I "hot swapped" the bulbs a few days ago.

Any ideas???

 

[Yupster Dog]

Not sure how to check the relays

Switch out relay with another same relay to check. If it is still the same the only thing left is the modified switch.

 

[Tjhoward84]

Switch out relay with another same relay to check. If it is still the same the only thing left is the modified switch.

I did swap out the fog light relay for a known good one and I have a new (junk yard) switch assembly. Using the junk yard switch assembly yields the same issue. I will swap out the headlight relay - I haven't done that yet.

 

[Anthony DeVor]

Please update if you haven't figured out the issue yet, I am a guru when it comes to LEDs and electrical so I am more than willing to help.