Hardiwiring Power for C125

[Stephen Dean]

And Subaru's are not that complicated either, in comparison to some other cars on the road.

Which model of Subaru do you have?

[FoxSTI]

I have a 2015 STI. would love to put in a PDM and button in it.
I have a C125 at the movement that I am working on configuring.

[FoxSTI]

Guys so I have been thinking and doing quite a bit of reading.

I have decided to power the C125 with 12V from the battery through a relay. The relay will be switched some a 12v wire on the inside fuse holder box.

I am building a mini harness with a relay and some fuse holders just to bring 12V and switch it on.
I am using 18 AWG for the fused power lines and ground. Then I am using 14 AWG for the 12V and Ground across the relay from the battery. I am just wondering if that will provide adequate current in the case I wanted to go to a break out board like some of you guys have done. 14 AWG wire should be able to carry at least 20A. to power more than then C125 possibly other equipment ?

[the_bluester]

Unless you are later on going to put a heap more load on it then even #14 is probably overkill. The standard looms use #22 power wiring for the C125/C127. One thing I would do (Given you do not have a PDM) would be to fit an appropriately rated self resetting circuit breaker to the battery supply for this relay. Far more convenient than a fuse.

I can not recall exactly what it was but I did see a friends data log from his race car and the PDM output which was powering his C127 was sourcing very little current. I don't think it was even as much as 1A although he does not have any sensors supplied off his dash, all his data is sourced from his PDM and ECU.

[FoxSTI]

Hey Blue, I went to Advanced autoparts today picked up 14G SXL wire rated at 17A and 125C (heat).
The bay on the STI is extremely hot. I decided against the 12G. I was thinking since I do not have a PDM yet and the 14G seems is less ridig. I realize the when the time for a PDM comes I will need to run #8 Gauge or something hefty you like you.

All I have in the car for now is my LC2, the C125 with possibly 3-4 sensor (5v).

I was looking into the circuit breakers. I guess the advantage is not having to replace a fuse and "it will reset it self" as long as the current rating is not exceeded?

Anyway, this mini harness will convert to 18G on the inside of the firewall after the relay, where it connects to the LC2 and C125. I am also leaving a free connection for an additional piece of equipment should it come up.

I have a Hella "weather proof" relay holder with some #12 pre-installed leads that I plan to switch 18G for this exercise.

I am using NTE brand stranded wire for this, I have not stepped up to milspec wire. Not sure how beneficial it really is.


EDIT: I just looked up the milspec wiring it is all rated up to 150C. and its claimed to be lighter than conventional wiring. I will be out out town this weekend so I am order some Milspec wire. I may as well go all out / do it right. Price is very similar to what I am getting locally at the autoparts.

[FoxSTI]

Does anyone know if I need special wire strippers for the milspec stuff?

[the_bluester]

The Tefzel coated and similar cabling can be pretty tough to strip so you do need a good set of strippers. I have a pretty basic set but it takes a lot of care to get a clean strip without nicking the conductors and weakening the wire.

I am borrowing a set like these this weekend from a friend who has just finished his PDM install, although he did not pay anything like the price on this site for them. This style allow a lot better control over stripping and better gauging of how much you are stripping than the pliers style sets.

http://au.element14.com/ideal/45-672/wi ... AGPSPN=pla


EDITED TO ADD: If you happen to buy a good set of strippers, don't use this part number, it is just an example, this set is for #24 to #30 wire.

[FoxSTI]

do you think I can borrow it next ? lol
Thank for clearing that up.

[the_bluester]

The Motec guys might be able to comment, but these might be a good set.

http://www.ebay.com/itm/Ideal-45-092-St ... SwEetV8IIU