Heres one for the wiring gurus. We all know that when the high beams are turned on the fogs go off. The fogs can be turned on or off when the low beams are used. How would one modify this stock set up so that when either the hi or low beams are being used the fogs can be turned on or off at any time at will. I do not want my low beams to be on at the same time as my high beams.


Would a jumper be needed or a differnet program in the BCM?


Thanks for your advice


AbsoluteGMCEdited by: AbsoluteGMC

Actually after careful inspection we determined that you would have to install a separate switch in order to make this work. The lights will work with this setup but you will not be able to turn them on and off...http://dieselplace.com/forum/uploads/44Z_hifogonly.JPGEdited by: GMC2500HD

You could do it easily by adding in another switch.

Another switch ? Do you mean to say that the low beams use one switch and the highs would use another?


The red line in your picture would be a jumper right?


I am an Electrician by trade maybe If I had a schematic of how the lighting system worked as a whole ( Hi, low beams and fogs) I might be able to figure something out only thing it might take alot more work.


Thank you for your response it was greatly appriceiated.Edited by: AbsoluteGMC

Talk to Max Power he had something figured out. We talked about too. I think he had another idea for you on this.

They are controlled through the BCM. You can't just ground one side of the switch in the cab because the signal only goes back to the BCM. The Fog Lamp Relay control comes directly from the BCM, so the easiest way to do it is to add a diode and a switch inline between the high beam and fog lamp relays, that way they will work with the high beams automatically and if you want to turn them off, just flip the switch.


Dennis

You could also wire it up like this. This way you can have the fogs on automatically when your high or low beams are on as long as the new switch is on.


http://www.dieselplace.com/forum/uploads/MVC-003S2.JPG

What if you bypassed the entire BCM and just switched the ground of the fog light relay. Then you could just change the switch in the dash to a maintained contact type of push button (similar to a ball point pen) from a suitable gmc part and it would look the same but function independantly of the other lights in the truck. The BCM would just think that you never used your fog lights at all.


Here is my drawing. What do you think?


fromhttp://dieselplace.com/forum/uploads/Fog_light_Mod.jpg

The only thing wrong with that is that because you are supplying grond to activate the relay, you would be able to leave the fog lights on even when the truck is off or the headlights are not on. So you would either need to supply the other side of the relay with a switched ignition or add another relay to only provide ground to the OEM relay when the ignition is on. Too much hacking for my liking. But it would work.

Does the 12v remain present at the hot side of the fog light relay even when the truck is turned off?


On second thought why dont I just Install some nice aux. driving lights... OH Yeh thats the ticket!Edited by: AbsoluteGMC

I honestly don't know. I would assume so, but I have never personally tested it. Even if that were the case, the fog lights could still be on during the day when no other lights are on.Edited by: Max Power

Yes, it is hot at all times.


Dennis