Possible to reuse the OEM wiring harness?

**hutacars** · 08-06-2009, 08:20 PM

I've removed my head unit, and was wondering if I could reuse its wiring by connecting it to my P2140. It has all the wires I need (12V, Ground, and Ignition), so I don't see why it should be a problem-- at least in that respect. However, I don't know if the wires are thick enough to carry enough current. The P2140 calls for both of its 12V wires to be connected together and to the 12V source, so while individually each wire seems to have the same gauge, the P2140 may try to draw more current than the car's wiring can handle. I would like someone to please confirm if this is the case.

Also, will this be a problem with grounding as well? Or should I not have to worry about current with grounding?

In addition: if I can't reuse the wiring harness, how do I send an ignition signal to the P2140? Or can I just use that wire, since the gauge is the same and I don't have to connect two wires from the P2140? Also, the ignition wire says it sends +12V, not just a signal. Is that a problem, or is that the way it's supposed to be?

Sorry for all the (newbish?) questions.

**csfile** · 08-06-2009, 09:54 PM

I'd say it would be safe to use the ignition wire. Only use the 12V line if it is a large enough gauge. Use this as a guide for gauge/amperage: http://www.mp3car.com/vbulletin/advf...iew&advfaqid=5

ground should be at least the same gauge as the 12V and try to keep it as short as possible.

Edit: Since P2140 is 185W (even though you may not use the whole 185W), use at least 14awg if 10ft or less of wire. But I'd recommend going a little larger (12awg).

**hutacars** · 08-06-2009, 11:06 PM

Thank you for pointing me at that very helpful guide. Considering I was pointed at FAQ pages twice today... I'll take it as a sign that I ought to check the FAQ's before I post

**soundman98** · 08-07-2009, 10:02 AM

from a reliability standpoint, it would best to run a new, dedicated power and ground wire to the power supply. this will also simplify trouble shooting if you run into any problems later-- because it is very possible that multiple devices are drawing off that wire (in my car, the dome light, chime, and radio, and clock pod all use the same wiring/ fuse).

it might work to draw off the factory wiring, but the first time i tried it in my install, i blew 2 of the factory wiring fuses that controlled most of the car functions-this resulted in a trip to the dealership-because auto makers like to hide certain fuses--i was also trying to use a defective m4, so that could have also been the cause.

it will take some more time, and sometimes a few choice words, but in the long run, a dedicated power wire off the battery is the best.

**hutacars** · 08-07-2009, 11:29 AM

What do you think of a wiring kit such as this to connect the P2140 to the battery?

**Bugbyte** · 08-07-2009, 11:34 AM

That looks like it will work. Don't use the car's wiring. Run new wires. I have been running my Mini and a 2140 with 8 gauge wires and haven't had any problem.

The car PC 101 video in my signature link explains how I set up the 2140 for the Mini.

**hutacars** · 08-07-2009, 01:31 PM

Very helpful video, thanks! I don't have any "fusable links" however, just two ordinary fuse boxes, so I'll likely end up running my power cable directly from the battery, with my own fuse in the middle. I'll probably follow the procedure outlined in the book "Geek My Ride," including the bit about the terminal strip to connect devices.