Car Stereos: Installing Amp on OEM HU on 2005 Silverado, chevrolet silverado, fuse block

Question
QUESTION: Justin,

I've installed an amplifier to power a subwoofer in my truck using the factory head unit. I've got everything working properly, but since the factory head unit has no remote power-on or power antenna wire to connect to my amp, I've used a fuse tap for the amp to turn on. The problem is, the amp stays on- draining my battery over night. The fuse I've tapped into is the "Radio" fuse in the fuse block under the hood. If the "Radio" fuse is not one that shuts off when the ignition is switched to the "off" position, which fuse can I tap into so I won't have to jump start my truck to come to work everyday?

Thanks,
Mike

ANSWER: Hi Mike,

Fuses all receive power pretty much all the time. It's up to relays and switches farther down the circuit to disable the flow of electricity.

What you'll want to tap into is the switched power wire behind the deck.  The one that tells the deck when it should be on.  This wire is usually (and confusingly) yellow on GM factory harnesses.

Justin

---------- FOLLOW-UP ----------

QUESTION: Justin,
I've found this information from a website listing what the wires are for the HU in question. It states that the switched ignition for the radio is "Class 2 Serial Data". I have no idea what that means. The info. I received is as follows:

2005 Chevrolet Silverado Car Stereo Radio Wiring Diagram:

Radio Constant 12V+ Wire: Orange
Radio Ignition Switched 12V+ Wire: Class 2 Serial Data
Radio Ground Wire: Black/White
Radio Illumination Dimmer Wire: N/A
Radio Antenna Trigger Wire: N/A
Radio Amplifier Trigger Wire: Pink
Front Speakers Size: N/A
Front Speakers Location: N/A
Left Front Speaker Wire (+): Tan
Left Front Speaker Wire (-): Gray
Right Front Speaker Wire (+): Light Green
Right Front Speaker Wire (-): Dark Green
Rear Speakers Size: N/A
Rear Speakers Location: N/A
Left Rear Speaker Wire (+): Brown
Left Rear Speaker Wire (-): Yellow
Right Rear Speaker Wire (+): Dark Blue
Right Rear Speaker Wire (-): Light Blue


ANSWER: Hi Mike,

The class 2 serial data means you have one of the GM systems where the door chime, and various other buzzers and bells are piped through the stereo.  In this case, you should still be able to tap into the wire since you're just using it as a switch.  The only question is what colour is it?  You can find with a multimeter by disconnecting the harness from your factory deck, putting the car in accessory, setting the multimeter to VDC, putting the black prong on ground somewhere on the car (any unpainted metal), and the red prong on harness wires until you find 12V.  Then make sure the 12V goes away when the car is taken out of accessory.  Anywhere you can get 12V switched is OK though, so if your car has an external clock, or cigarette lighter, and they lose power when the car is off, you can use those too.

Justin

---------- FOLLOW-UP ----------

QUESTION: Justin, I used a light meter to find a fuse that would shut off when the ignition switch is off. I removed several fuses until I found one that would shut off when the ignition is off and turn on when the ignition is switched on. The amp works fine and now my truck will not start. It won't even turn over, even when using jumper cables to another vehicle. I guess my next question deals with not the amp, but my ignition on my truck. What can I do to solve this problem? I went back and double checked the fuses I tampered with, and they are not blown. Is there something that needs to be "re-set" for the computer/ignition/starter?
Thanks,
Mike

Answer
No, there shouldn't be anything that needs to be reset.  The most likely scenario is simple that you've either not replaced a fuse in the right place, or blew one in the process of swapping them out.  Some fuses don't look blown even when they are.

Not even turning over means simply that the starter solenoid isn't sending the 'start' signal to the car (which is why jumpers won't help).

Another possibility is that in the process of fishing for wires to tap into, you knocked the starter solenoid's harness loose from the ignition column somewhere.  Check around where you were looking and where you may have placed any stress on the wiring in the process of locating the amp wire, and make sure all of the clips are securely fastened in place.

Also, if you weren't anywhere near the ignition colum, another possibility is the park/neutral sensor switch or the clutch switch if it's a manual transmission.  Most cars will refuse to start if you don't clutch to the floor in a manual, or have the car in park in an automatic.  If you were anywhere near those, check those wires and harnesses too.

Good luck,
Justin