I'm trying to install a car stereo in a Jeep Compass 2010.

The third-party car stereo came with a red cable that I'm supposed to connect to a fuse. It's marked as 12V ignition.

However, the OEM car stereo was not connected to a fuse. It was just connected to the car's connector and to the antenna. So my assumption is that the car's connector already provides the 12v ignition source, otherwise the OEM car stereo couldn't have worked, but it did.

Is this assumption correct? Do I really need to connect to a fuse even if the OEM car stereo wasn't?

  • 1
    Hard to say for sure, you may need to because the aftermarket stereo may have a higher-power amplifier that pulls more current than the OEM radio. Otherwise, it may not require it. Again, tough to say without more detail. – Shamtam May 14 '18 at 19:45
  • Welcome to Motor Vehicle Maintenance & Repair! – Pᴀᴜʟsᴛᴇʀ2 May 14 '18 at 20:19

The OEM stereo was most definitely connected to a fuse through the car connector. The fuse will be somewhere in the car's fuse box.

What you need to get is an adapter that connects to the car's connector and breaks out all the wires for power and for the speakers. Then connect the adapter to the new third party stereo. This way all the wires will go where they need to be and you don't hack up the car connector. These adapters can be found online or at Walmart.

That said, there are some cars that literally don't have an ignition feed in the car connector. They only have a battery feed and a data bus connection. GM is famous for doing this. The OEM stereo would get the signal to turn on and off through the data bus. The third party stereo would require stealing and ignition feed from something else or there was a third party box you could buy that would sit on the data bus and provide a signal to the stereo of when to turn on and off.

  • Thanks for your reply. I already bought an adapter and I connected the cables from the adapter to the third-party stereo by color. I then connected the adapter to the car's connector but it didn't work. I bought a multi-meter to make sure that I connected the cables properly. – user11081980 May 14 '18 at 20:12
  • @user11081980 Was the red wire left over after connecting all the wires to the adapter? – vini_i May 14 '18 at 20:14
  • Yes, the red wire was left over. The adapter didn't have a matching red cable so it was left over. – user11081980 May 14 '18 at 20:16
  • @user11081980 Then most likely the last paragraph applies to you. – vini_i May 14 '18 at 20:17
  • I see, thank you! I read that an alternative for my vehicle is to connect it to the cigarette lighter, given that the fuse box is under the hood. At this point I'll leave the installation to a professional. – user11081980 May 14 '18 at 20:25

This is an old thread but I was after the same info for a 1973 car with the same issue. The lighter tip worked a treat and didn’t need a professional - just hooked up the battery wire to the existing fused cable, earth to earth and the 12V wire to the lighter cable. Don’t need the lighter anyway... Thanks to all for the v useful question & ideas :)

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