Car Stereos: Car Stereo Wiring, car stereo wiring, mitsubishi 3000gt

Question
I have a Mitsubishi 3000GT and I had a pioneer 6 in Double Din Dash dvd/gps/cd/etc unit in there before I left the car at an auto shop and it got stolen so I bought a new system for it. Once I got the radio, a lanzar 6.5 in double din, it stopped working cause I guess I fried it because the guy that stole my radio cut my radio harness off to the stock wire so I just guessed where they went. So after that I got a pyle 7" motorized dvd/cd/etc unit. I also printed out a 3000GT wiring diagram so I could decipher each wire like the black wire with the red stripe is connected to the yellow wire or constant 12V+ and so on. After I matched up all the wires and so on. I connected the harness to the radio and nothing. I then turned on and off the car and it would come on then dim and shut off on its own seconds later. I thought it was the car battery and then replaced it and I got the same reaction. Then I replace the 10v fuse with a 15v and it reacted the same way. My car does have a stock amp. I don't know if I blew the amp fuse or need to replace the electrical fuse. I also have a aftermarket sub and amp system that is not yet installed. Every auto mobile sound installation place is backed up for weeks since the holidays and I travel a lot and it sucks w/o music. I'm stuck at what to do now. All that I can think of now is replacing fuses. Any ideas or a solution.

Answer
Hi Tony,

Head unit power problems are very easy to troubleshoot it you have a digital multimeter available, and very difficult if you don't.  You really just have to verify voltage on two wires:  the yellow constant power wire and the red accessory power wire.  

There's no factory ground wire in your vehicle's radio harness. If you have the head unit's ground wire connected to a vehicle wire, I'd connect it directly to the metal dash structure instead.  That should ensure a good ground connection.

You can't always trust wire color guides, so it's a good idea to use a multimeter to verify your wire functions.  (For example, my source shows a red wire with a black stripe for constant power, not a black wire with a red stripe).  Just test each of your wires until you find one with 12 volts regardless of the key position. This is the constant power wire. If you can't find such a wire, it's time to check your fuses.

Most vehicle have at least two fuses in the vehicle fuse box that supply radio power.  One fuse is for the constant power wire, and the other for the key-switched power.  The tricky part is that they may not both be labeled as radio fuses, so you need to test all your vehicle's fuses.  Again, a multimeter makes this easy.  Here's a guide to using a multimeter for vehicle fuse testing:  http://kzcarfi.blogspot.com/2008/08/testing-vehicle-fuses-with-multimeter.html

The constant power wire should be connected to the head unit's yellow wire.  Next, use the multimeter to find the accessory power wire (my source shows it as a blue wire).   The accessory wire will test with 12 volts when the key is in the ACC or ON positions, and 0 volts when the key is off.  This wire should be connected to the red wire at the head unit.

If you have a solid ground connection, and 12 volts on both the accessory and constant power wires, then the head unit should power up.  If it doesn't, then there's a defect in the head unit.  However, I suspect your problem is either a blown fuse, a poor ground, or a power wire connected to the wrong vehicle wire.  

If you don't have a multimeter, you'll definitely want to go and buy one.  It doesn't have to be an expensive model.  The cheapest digital multimeter available at any hardware store will work perfectly well for your needs.  Without one, though, it's almost impossible to do any  real troubleshooting.

Good luck!

Brian