What have I got wrong?

smitty_r51

Well-Known Member
Just finished wiring up a stedi light bar.
Specs say Current Draw 8.6A @ 13.6v

For this I had to do away with the supplied wiring kit as it wouldn't fit so picked up some 15a cable from Jaycar. https://www.jaycar.com.au/15a-twin-core-power-cable-sold-per-metre/p/WH3079


Problem is when I tested it the wiring got hot on the negative wire and it melted the 10a fuse. Ran it briefly connected to the terminals directly with the multimeter in between and it shows 12.7amp.


Are they that badly rated and do I need to increase my wiring to 25a, or is there something wrong with either my circuit or my test methodology?
 

CruisingSned

Active Member
Smitty
Your testing setup sounds right.
Did you happen to measure volts while running the light? As voltage drops current rises.
Are you sure you read the rating for the correct light? 12.7A sounds like a reasonable current draw depending on size of the light. It would be worth checking.

By melting the fuse, sounds like there is something wrong in the circuit as well. I would be guessing a bad connection at the fuse on the supply side to get it to melt if it didn't blow the fuse.

Are you able to post the model number of the light?
 

CruisingSned

Active Member
Rip it out have a coffee and start again youve crossed your + directly to Neg some how. And what sort of multi meter are you using ?
Generally a dead short would result in a lot higher current and massive voltage drop to the point where the LEDs wouldn't light up.
 

Colly18

Well-Known Member
I'd suggest look at a cross section of the wiring in the STEDI wiring loom and compare it with the Jaycar wiring to see whether you need to upgrade from 15 amp to heavier wiring.
Which STEDI light bar? would be useful information.
I recently fitted a STEDI light bar to a friend's vehicle with no problems. Like you, I found the supplied loom was useless, so I just rejected it and wired the lights with a relay triggered from a 'tap' into light high beam wiring. I went about 20 amp wiring and all worked well.
Some of those STEDI light bars are pretty bright things and I wouldn't be surprised if they draw more current than specs indicate(?)
 

Drewswb

Well-Known Member
Yup "Generally" but as hes asking if hes measured correctly Im wondering if the 12.7 measured is volts not Amps he wouldn't be the first to be befuddled by a multi meter (spent 10 min the other day with mine on hold )
 

smitty_r51

Well-Known Member
had an extra thought, because the relay was DOA, the wiring is the full length of 6.5m from the roll. Wonder if the length is adding some resistance.

Going to pull it apart tomorrow and recheck it all anyway and grab a new relay so i am doing it properly and see how we go
 

Petunia

Well-Known Member
Volts, Amps, Watts ...... so .... 8.6A @ 13.6v = 116.96Watts [cant argue with that, fact jack] so now knowing wattage working back from 12.7Volts @ 116.96Watts = 9.21Amps.
Therefore without engine running 10Amps draw, a 10 amp fuse will be on its limit of blow or go? I suggest 15amp fuse cures that portion of the potion.

As much as I love my local Jaycar, in this case I would suggest that there is an inconsistency with the wire size?

one : https://www.jaycar.com.au/15a-twin-core-power-cable-sold-per-metre/p/WH3079
is not consistent with
two : https://www.jaycar.com.au/red-15-amp-dc-power-cable-sold-per-metre/p/WH3073
cross referenced by
three : https://powerstream.com/Wire_Size.htm

A : Bigger fuse.
B : Bigger wire.
C : Happy smoke free light.

:cool:
 

TheregoesSteph

New Member
That wire is only 1.5mm =3mm auto. Rated at 15a on short runs, I wouldn't use less than 4mm auto cable for any light bar, and 6mm on bigger light bars or roof mounted.sounds like the wiring and fuses are too small.
 

smitty_r51

Well-Known Member
Looking at the supplied wiring from Stedi it isn't 8G, i am guessing it is 25A. Although they have that wired with a 60A Relay and a 30A fuse which is kind of a worry as that means the wire goes first :|

So would the recommendation be to go up to 25A https://www.jaycar.com.au/25a-2-core-tinned-dc-power-cable-sold-per-metre/p/WH3087
or 8G https://www.jaycar.com.au/8-gauge-figure-8-power-cable-sold-per-metre/p/WH3063

only difference is going to be how much bigger i have to make the hole in the roof (currently coming through the middle of the M5 captive nut built into the skin, will just drill the nut out)
 

Petunia

Well-Known Member
Looking at the Stedi wire? it may have black printing on the red wire? an AWG figure may be printed on the wire?

The best guess I can see from a Stedi wiring harness is 10AWG > Disclaimer: this is a figure quoted on a wiring harness NOT necessarily the actual harness supplied in the particular box in front of you?

8AWG being bigger than 10AWG will work, given extra overall distance of the circuit to the standard wiring loom provided.
 
The rating on the wire is just before the point where it starts to melt the insulation hence with your current draw its getting hot. As mentioned before its only 1.5mm2 conductor so not large enough when you factor in the distance. If you are running it to your roof a minimum of 6mm auto which is 4.59mm2 is more suitable, as Petunia mentioned 8AWG is ideal to eliminate volt drop. With 12 volt circuits distance has a huge affect. Hopefully in the future everything will be 48 volts.
 
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