Power IGN question

**Viscouse** · 08-18-2005, 04:32 PM

I understand perfectly how to wire up an Opus with the Constant power. Search helped with that. What I could not find was different loads for the ignition wire.
Opus needs Constant & Ignition power sources.
Here's my question.

I have an ignition switched cigarette lighter (which is not used for anything other than power). I already have an XM Commander (needs ignition as well) hooked into it. Can I wire an Opus 120W in there as well? Is the Igntion wire actually used or is it a "sense" wire to let the Opus know the vehicle is turned on & to go ahead & turn on/off.

Thanks...

**strohj** · 08-18-2005, 04:41 PM

its a "sense" wire so that the Opus knows when you turn your car on and off again

so unless your cigarette lighter loses power when you turn the car off... you cant wire it there

**ukchris** · 08-18-2005, 04:41 PM

I mailed Opus and they said there is practically no draw, it is only used for switching. I have mine sharing a connection to my screen, FM modulator and radar detector all through a 7.5A fuse and no problems.

**Viscouse** · 08-19-2005, 06:00 AM

Thank you kindly, that was exactly what I needed to know.

**CornToeGoblin** · 09-16-2005, 01:05 AM

Originally Posted by Viscouse

Thank you kindly, that was exactly what I needed to know.

you could always put in a fuse if you paranoid

**0okami** · 02-19-2006, 08:36 AM

Originally Posted by CornToeGoblin

you could always put in a fuse if you paranoid

what size fuse?

sorry had to ask.

**stapan** · 02-19-2006, 10:53 PM

you should absolutely put a fuse if the wire is thinner than the wire you are tapping into. while the opus itself may not draw a lot of power on this line, the purpose of the fuse is to protect the wire itself in case something bad happens and the wire shorts out. remember, this wire is still connected to a hot source of power, and if the wire gets in contact with anything grounded -- whether its twisted sheet metal in a car accident, or just getting disconnected due to shock or vibration and the disconnected end touching something grounded -- you're looking at a serious fire risk without a properly rated fuse. the best would be to use the same wire thickness (so its properly protected by the factory "cig lighter fuse") or if needed use a lower rated cig lighter fuse than factory

**0okami** · 02-20-2006, 12:22 AM

Originally Posted by stapan

you should absolutely put a fuse if the wire is thinner than the wire you are tapping into. while the opus itself may not draw a lot of power on this line, the purpose of the fuse is to protect the wire itself in case something bad happens and the wire shorts out. remember, this wire is still connected to a hot source of power, and if the wire gets in contact with anything grounded -- whether its twisted sheet metal in a car accident, or just getting disconnected due to shock or vibration and the disconnected end touching something grounded -- you're looking at a serious fire risk without a properly rated fuse. the best would be to use the same wire thickness (so its properly protected by the factory "cig lighter fuse") or if needed use a lower rated cig lighter fuse than factory

so in short, if its a positive/hot/+ wire, always fuse it near the source. correct?
*takes note*

**piabu** · 02-20-2006, 01:06 AM

Originally Posted by 0okami

so in short, if its a positive/hot/+ wire, always fuse it near the source. correct?
*takes note*

The fuse is actually to protect the battery.

The idea of fusing as near the battery as possible is that in the event of a short-to-GND, the battery would not continue to drain with a large current until it dies (or until something catches fire from a spark or overheat).

By fusing close to the battery, you also reduce the length of "hot" wire that may melt or spark or otherwise be vulnerable.

**spuzzdawg** · 02-20-2006, 10:02 AM

Originally Posted by piabu

The fuse is actually to protect the battery.

The idea of fusing as near the battery as possible is that in the event of a short-to-GND, the battery would not continue to drain with a large current until it dies (or until something catches fire from a spark or overheat).

By fusing close to the battery, you also reduce the length of "hot" wire that may melt or spark or otherwise be vulnerable.

I don't know how you worked this out. It's standard practice to fuse electronic items - The first thing a textbook will tell you is that fuses ONLY save electronic components - not people. I guess a battery prob counts as an electronic component but i wouldn't say "the fuse is actually to protect the battery"

My understanding of why the higher power cables are fused close to the battery is to reduce the length of positive cable protuding from the battery in the event the fuse holder came apart. The ideal length therefore would be to place the fuse at a distance less than the closest metal surface to the battery. I think this may be what you were trying to say - but I couldn't really make sense of your comment

Spuzzdawg