H4`s and 14GA ground wire.

[911SC Pilot]

As some or most know, Im installing H4`s .

I have a guestion. Is it ok to run 14GA wire as my ground, even if I ran 12GA for the rest of the set up ?

I was trying to keep the same colors for the wiring, but i could only find brown in 14GA, really didnt want to go with Black 12GA.

[Bob's Flat-Six]

Wouldn't matter, Just as long as it's a good ground, might even be better.

[911SC Pilot]

Originally posted by Bob's Flat-Six
Wouldn't matter, Just as long as it's a good ground, might even be better.

The answer I needed, thanks, Now I can finish with all the pre wiring.

[Jim Sims]

If that's the only ground then all the current will have to go through it. It should be sized to match the power side; if you can't find 12-gage in the brown run two brown 14-gage wires in parallel. Jim

[Bob's Flat-Six]

My Bad, I was thinking it was a bigger sized when it's smaller, I should leave it to the eletricle experts. I would use the same size or double up.
Sorry

[911SC Pilot]

Originally posted by Jim Sims
If that's the only ground then all the current will have to go through it. It should be sized to match the power side; if you can't find 12-gage in the brown run two brown 14-gage wires in parallel. Jim

So I need to go buy 12GA. I guess it shouldnt matter, color wise.just as long as I have the correct size. Dont want to run more wires.

[Randy Webb]

None of the answers above is correct. YOu need to size the wires based on the power draw. IF the power side is correctly sized THEN you can follow that -- IF the lengths of the runs is the same.

You need to have a negligible resistance in the wiring, hence getting nil voltage drop. You can try the small ga. wire and measure the voltage with all the power draw items operating by using a good volt meter.

OK? So the basis is the resistance/voltage drop -- everything else is just a rule of thumb.

IF you need a size and don't like the color then just use the "wrong" color until you find and buy the "right" color wire.

[Jim Sims]

Oh brother! What do you suggest for nil voltage drop? A microvolt? This isn't a cellphone or satellite; a little wire weight is better than a fire. Wiring can't be exactly optimized unless you are willing to draw custom wire gages. Jim

[jazzbass]

Use 12ga wire. As a rule of thumb all the conductors the same size - its a circuit. If the positive side is carrying 15A into the headlight, then the ground has to carry 15A out of the headlight.

Now, if you're an EE or have studied these things you'll know that the real purpose of sizing wire is to eliminate as much resistance as possible, like Randy said. The resistance of wire varies proportionaly with the length and inversly proportionally with the square of the radius of the wire. This is given by the equation R = pL/A, where p = 1.72E-8 Ohm-meter for copper. To the point, if the wire is smaller (14ga vs. 12ga), but the lenght is shorter than the 12ga run, you might be OK.

If you think all that seems way too overanalyzed and involves too much electrical theory and math for a simple headlight install, you're absolutely correct. Buy 12ga wire and be done with it. Use black if you have to.

[Randy Webb]

Ok, lets make it simple -- do what the factory did. You'll be fine.

If the length of the run on the power side is the same (and you have that stock wire) then just do that.

You don't need the size exact - just step up a notch in size to be more safe....

[911SC Pilot]

LOL, I love you guys.

My space shuttle will be launching next week.

No, I went and bought 12GA black wire and said screw it. The car isnt going anywhere, not selling it, so who cares.

But, I do have another guestion. Is it ok to run the headlight ground to the same point of contact that the relay ground will go ( to the body, at the point of the battery ground), or do I need to find seperate ground sources for both ?

[Jim Sims]

All grounds are equal (no wise cracks about ground loops from the EE's); you can use the same ground point for the relay and the wire. Jim

[911SC Pilot]

Originally posted by Jim Sims
All grounds are equal (no wise cracks about ground loops from the EE's); you can use the same ground point for the relay and the wire. Jim

Thanks Jim.


.,.,.,.,.,.awaiting wise cracks

[RoninLB]

Originally posted by 911SC Pilot
LOL, .

No, I went and bought 12GA black wire and said screw it.

if you have any electricians green vinyl tape.. wrap at least both ends on top of the shrink..

[911SC Pilot]

Originally posted by RoninLB
if you have any electricians green vinyl tape.. wrap at least both ends on top of the shrink..

I have many colors of 3m Elec tape. what do you mean buy wrap both ends ?

[RoninLB]

Originally posted by 911SC Pilot
I have many colors of 3m Elec tape. what do you mean buy wrap both ends ?

green is a common color for elec ground.. wrap a "marker"..
a tape width is fine.

[911SC Pilot]

Originally posted by RoninLB
green is a common color for elec ground.. wrap a "marker"..
a tape width is fine.

A Marker as in writing ground on it ?

If so, I revising a diagram that Jadams1 put in my H4 post.,.,



.,.,.and Ive placed the colors I used, with a 4 relay set up, so i will have a diagram for my H`4 upgrade post I`ll create(with pics), and put a copy in my Porsche folder, for future reference.

[palle7688]

I believe braun is ground in P-cars, like in chart above

[RoninLB]

Originally posted by palle7688
I believe braun is ground in P-cars, like in chart above

your correct..
maybe I shouldn't have said green.. I've always used green because it's much easier for me to distinguish. and brown is not the routine elec shop tape.. I guess if I see green it jumps out and screams ground..

[Jadams1]

911SC Pilot, you have a PM.