Question on which wires to radio work with ignition
 

Hi all. I am going to hardwire my Garmin GPS to my 99 C5 and would like to jump power from behind the radio, so the plug can come up through my dash and into the bottom of the GPS. I would just like to know which wires on the radio harness I should connect my red and black wires to, for this unit to turn on and off with the ignition switch?

I have already hardwired my Escort Passport detector to my passenger footwell, but would like to come off of my radio with this install so I can run my cable from underneath the unit, rather than from above through the mirror panel. If anyone can provide me with what wires I should jump my hardwire off of to work with the ignition, it'd be greatly appreciated. Thanks!

Yellow for ign. switched 12v and use chassis ground because there is more than one black wire and they're not all grounds. There is also more than 1 yellow, so verify it with a DMM or test light.

There isn't an 'ignition' wire at the stock GM head unit... it is turned on via the serial bus commands.

Do you still have the stock GM stereo or an aftermarket HU? If it's aftermarket and you are using a PAC adapter, then tapping the yellow wire and a chassis ground will work.

If the stereo is stock, then there are a couple of ways to get a switched ignition source, one of which you have already done. (Wiring harness in the footwell.)

The other ways are to tap the ignition switch (I don't necessarily recommend this) or tapping into the fuse panel in the foot well.

As much as I hate to tell you this, tapping into the harness in the foot well is really the best solution. Good luck.

Mark

:iagree: Better to go in through the footwell

Hey everyone and thanks a ton for your help. I am using a stock GM head unit currently, so I am assuming using the yellow wire will suddenly not work? My main issue is that the hardwire kit is not long enough and I'd like to come from under the unit anyhow, since the USB head is angled to be connected from below. Seems I am in a bit of a pickle, and sounds like I need to just elongate my hardwire and go through the footwell again as my only solution. Thanks for your help, everyone.

Well that's the thing... 'the yellow wire' is an aftermarket description for the accessory wire. It's the 'standard' color for the accessory/ignition wire in the aftermarket world.

GM doesn't follow this 'standard' and does their own thing... as do many, if not all, of the OEM's.

So no... there isn't a 'yellow' wire in the factory GM head unit in that regard. Matter of fact, there isn't even an accessory wire either. The serial bus in the C5 is what tells the various devices to power up. Which is why you would use a PAC adapter if you wanted to add an aftermarket HU and keep a few features. (Like the radio staying on after you shut down the car.) So basically... there isn't a 'yellow' wire, nor is there an accessory/ignition wire in the center console of the C5.

I don't see any reason why you couldn't splice the new GPS wiring inside the dash area by the radio and run an extension wire down to the footwell. A simple 14 or 16 AWG black/red from Radio Shack with a couple of butt splices at the GPS, then a couple of wire taps at the GM harness. Should be a piece of cake.

Mark

I'll be sure to give it a shot then Mark. I was expecting a may have to remove a good bit of the dash to do that, but maybe not. I'll go tackle it today and see how it turns out! :) Thanks again for your guidance.