Copied this from my other thread since its a new problem. So I am assuming I have a bad ground but am open for suggestins. Wired everything up last night for my new tranny temp gauge and appeared to be working. This morning driving to work everything was screwey. 1st off, I have driving lights wired in with power from the baterry and grounded to the parking brake assembly under dash. I got my power for new gauge from fuse panel and used same ground as was used for driving lights. I got power for the gauge light coming from the parking lights so it only lights up when headlights are turned on and used same ground as I did for the rest.
I think the power from parking lights is backfeeding the rest of my added electronics. When I turn on the headlights my driving lights switch now illuminates like they are turned on and my new tranny gauge works only with lights on but the backlight for the gauge does not turn on. My assumbtion is the grounds all tied together is my problem. Any suggestions?

 

Link to my original post.
https://www.f150online.com/forums/sh...d.php?t=433257