2008 f150 +12v constant location dilemma

power at the ignition is fine isolating the switch with the relay would prevent damage to the switch, however this vehicle uses positive lights which isn't very high current to begin with. wont be any problems.Ted

2nd Year Tier 1 Medical School

Still installing as a hobby...pays for groceries

Compustar Expert

The relay isn't there to protect the switch. The relay is there to allow for proper interface of the light switch wiring to the SJB. The SJB reads the position of the switch to determine which operation is desired. The switch has three (or four) positions, each of which applies a ground to the SJB. If a ground is applied to the SJB in the 'OFF' position, the ground needs to be removed from that wire in order for a different mode to be desired whether it is 'AUTO','PARK',or 'HEAD'. That is the purpose of the relay, isolating the ground input/common to the switch.

firebirdude wrote: yellow_cake wrote: Lol, I faced the same dilemma. I used the one in the ignition, no problems so far. https://www.the12volt.com/installbay/forum_postsm.asp?tid=135629 Using positive parking lights too?

Yes, I used the + parking lights as well. No issues. I wasn't comfortable about it before the install but when I saw how thin the parking lights + wire was, it seemed to be of a very low current.