jb451

Hey guys, i have a few newb ish questions.

I bought a relay upgrade harness, conversion headlight lenses and H4 bulbs, and i also found a set of work lights out at the junkyard. I plan on running all of the power wires to a distribution block out of an 80's chevy pickup.

Distribution block-


aux lights-


planned set up-


Question 1- The upgrade harness i bought comes with an already built in 30A fuse, and both H4's are 55w. (autopal brand) I plan on running 55W H3 bulbs in the auxiliary lights. When i do the math- 55Wx2=110w, 110/12V=9.16amps, I get roughly 9 amps for the aux lights, and that should be the same as well for the head lights. So should i run the 30A like the headlights or is 10 okay? My math process may be wrong as well, so if it is, let me know.

Question 2- On my diagram, from the battery to the distribution block, do i need a fuse? If so, is the size dependent on the total amount of wattage from all attached items?

Question 3- what gauge wire should i use on both battery to to block and block to aux lights? i was thinking 12g from the lights to block, and 2 or 6 gauge from block to battery... Y'alls thoughts?

FWIW, in the future i do plan on adding 4 more lights on the roof, and electric fan, and possibly a winch (i'll probably install a second battery for that though)

Thanks guys

Justin

dropzone

iTrader: (6)

You really should install a relay and a fuse for the aux lights

jb451

Thanks Dropzone, i forgot to add the relay and the switch into the diagram! Actually, i forgot relays and switches for both sets of lights...lol

Hadmatt54

Your circuit wire size and fuse size should be appropriate for the total load on the circuit. You of course want to co-ordinate your fuse size so that your smallest fuse closes to the load blows first in case of a fault. That distribution block looks like it has 3/8" studs, which would probably let your truck melt around it before it ever fails, so you can rule that out!
The wire from your battery to the block needs to fused close to the battery as protection for the entire circuit. You will be able to run 3 circuits from the block(if you don't double anything up). If you make one of these a control circuit for your relays that control the other circuits, your switches don't need to be high current and can be wired either switched power or switched ground.
Your circuit integrity is only as good as your weakest link. From the picture it looks like the auxiliary lights are wired with 18-20 gauge, so unless you change that wire as well ,wiring your circuit with 12 gauge won't be much of an advantage. Current flows on the outside of a conductor, that is why the larger the conductor the easier it for current to flow, but if you wire your circuit with 12 gauge and tie it the smaller wire You will have a bottleneck at the smaller wire and you are still going to get a substantial voltage drop across the smaller wire. Remember that 55watts is the max one of those lights will put out, at 12vdc. It is 4.58a. If you decrease the voltage you will not get 55watts output from your lights. Wiring a resistor into the circuit would have the same effect.
The new headlight circuit should be easy, you just use your old wiring/relay to control the new.

jb451

HadMatt, thanks for the great info!

The wires coming out of the light itself are attached to the bulb, so they were gonna get replaced as well!

So my fuse closest to the battery needs to be close to the amount of amps i am pulling through the entire system? (in this case a 20 amp fuse)

Hadmatt54

Start with 20a, I'd use 6 gauge from the battery to the block, that way if you find that 20a is not sufficient you can increase the fuse size without any damage to your wire.

jb451

right on, thanks bud!