h4 bulb wiring question

[spyghost]

hi,

i noticed that there are two kinds of wirings for h4's that the manufacturers use for stock wirings:
- switched ground, common positive
- switched positive, common ground

what are the benefits/disadvantages of each?

i am planning to upgrade my wiring harness such that one relay controls both lows and another relay controls the highs. question now is, which among the two should i use?

i know that the stock wiring doesn't matter anymore for pins 85 and 86 since they only provide the signal to the electromagnet, but my dilemma now is for the 30 and 87.

common positive or common ground?

 

[tom slick]

You match it to your car's existing wiring. Most cars are switched positive but some , such as toyota, are switched negative.

 

[eljefino]

I like wiring switched ground. Give each side a seperately fused +12v. Then if a fuse goes you still have light.