I installed two forward facing driving lights on my grille guard. They are wired to my battery (with an inline fuse) and wired to a switch on my dash. Both lights are well grounded as is the switch. Everything was working fine. Later I installed to auxillary back up lights. They too are wired direct to my batter with an inline fuse and are also well grounded. But after I installed the back up lights, whenever I turned either my forward, or rearward facing aux lights my gas guage quits working. It shows I have less fuel than I really do. Do I have a short somewhere? I drive a '97 4Runner 4X4 SR5. These are my only extra/after-market/auxillary items with wiring.

 

ehh id really recommend getting some relay's and wire the lights up right and use good wire min 14ga

here's how to wire up the relay
http://www.4runners.org/image/hella5...auxfusebox.jpg

 

Hopefully that'll fix it...but if it doesn't...any other ideas?

 

You've got mutual induction! The high current in the lighting wiring is affecting the low current signal from the fuel guage sensor. You could try running the wires differently, but the best way is to use relays. Relays will save your switch and keep all of the high current wiring out of the dash.

 

Awesome info. Thank you!