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I recently bought a 06 Chevy Impala. The radio unit does not turn on (no lights, no sound, no response). There is no voltage at the harness.

But there IS voltage at the fuse. So the break must be somewhere between the fuse and the radio.

How do I determine where the break is without tearing apart the entire dash?

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    Have you thought about just running a new line from the fuse to the radio? – Pᴀᴜʟsᴛᴇʀ2♦ Aug 4 '18 at 19:12
  • @Pᴀᴜʟsᴛᴇʀ2 Yes I just might do that. My only worry is that there might be other breaks in the harness. – x0a Aug 4 '18 at 19:14
  • Can you confirm there is power on both polls of the fuse? Is there an aftermarket radio installed? Just from experience-I work on a lot of GMs-there aren’t known problems with the radio power circuit on these, unless an aftermarket radio is installed or the vehicle has suffered some kind of damage or flooding. Either way it’s a fairly straight run from the underhood fuse block to the radio-through the firewall into the passenger floor area and to the radio-. You should be able to pull the glovebox or lower panel and expose most of the in cabin wiring. – Ben Aug 5 '18 at 7:32
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There are two possibilities, in my experience, either:

1) the wire is broken in the first few inches of the connector - either end and pulling on it or chopping it back may show you which.

2) the wire has broken inside the harness - for this, there is usually some sign of damage at some point.

If it is not (1) above, then the easiest solution is to run a new wire from the supply point to the device, note if this supply also powers other devices then connecting to both free ends may solve that issue as well...

The time and effort in opening the harness is not worth it unless there is significant damage that has to be repaired...

Edit: the other thing to check is that you have 12v both sides of the fuse - visually checking is fine but the element can fracture and the fuse looks good but isn't, so checking with a meter is necessary.

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While I am not at all versed in electronics, a guy who was told me they have a method they use to find an issue in most any electronics. This same method would work with just wiring alone. The simple method is to divide in half. What I mean by this is, you have a length of wire. The bad spot is somewhere within the length of wire. Find the approximate center of the wire and check the continuity from the center to one end. If you have continuity, check it from the center to the other end (just to prove to yourself you aren't going crazy). From the center, you divide the wire in half again, starting from the center of the 1/2 you're working on out to the end and to where the center you just tested from is. One side or the other is going to be dead. Continue dividing the wire by 1/2 until you find your break. Now, you aren't physically dividing it, just testing 1/2 at a time. All this takes to do this is a multimeter which will read continuity, time, and patience.

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    So, all you need is to cut open the harness at the relevant half-way points... Good method when wires are loosely tied together as in most electrical cabinets but a bit different with a harness that is usually fitted up behind the dash of the car with very limited access... – Solar Mike Aug 4 '18 at 19:28
  • @SolarMike - They did include the word "cheaply" ... I guess they also stated they didn't want to tear the dash apart either. Been my experience "cheap" and "easy" should never be used in the same sentence, because they are pretty exclusive. – Pᴀᴜʟsᴛᴇʀ2♦ Aug 4 '18 at 19:34
  • @Paulster2 now that analysis of cheap and easy I agree with :) – Solar Mike Aug 4 '18 at 19:38

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