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I have a 1997 Ford Expedition, which, when I bought it, only the speaker in back left door was working. The sound quality was fine, so I made do with just the one speaker. But a couple days ago, while the radio was playing, I heard a loud sharp pop, much like a gunshot, followed by a distinct electrical burning smell that faded away after about 30 seconds. The instant I heard the pop, the speaker stopped working, and it's been silent ever since.

The head unit seems to still be functioning fine. The radio was not playing very loud, so I don't think the speaker was blown, but I'm not sure how to begin trouble shooting. The only thing I did was pull out the speaker, which is a 4 ohm speaker, and run a resistance test on it. I got a steady 4 ohms, which I think means the speaker is still okay, but I'm not sure. Does anyone know what other tests I should try to figure out what broke?

I'm mechanically proficient, but I only have a very rudimentary understanding of electrical stuff, so while I can fix the problem once I know what it is, I just don't know how to go about diagnosing the issue. Any help would be so much appreciated!

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  • The easiest way to check the speaker is to hook it up to another source. I would bet a capacitor blew in the head unit, but that is dependent upon where you heard the pop come from. I'll still give you 10 to 1 that the head unit is actually fried, unless you have an amp (which you may or may not know about). A lot of Fords I've seen come with amps. The Expedition being a relatively high end vehicle should have one installed from the factory.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Mar 14, 2015 at 3:25
  • My model does have an amp somewhere, since I did have to connect the amp wire to the head unit when I installed an aftermarket head unit a few months ago. Assuming I can locate the amp, how do I test it? Also, I'm pretty sure I heard the pop coming from behind me, so I don't think it was the head unit. Would the head unit still appear to be functioning normally on the LCD if it had fried?
    – Timothy
    Mar 14, 2015 at 6:50
  • If the head unit's internal amp was fried, then yes, but since you said there's a factory amp, I'd go with it as the culprit. You can probably do a search online for where it is located in the vehicle.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Mar 14, 2015 at 10:39

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The easiest way to check the speaker is to hook it up to another source. I would bet a capacitor blew in the head unit, but that is dependent upon where you heard the pop come from. I'll still give you 10 to 1 that the head unit is actually fried, unless you have an amp (which you may or may not know about). A lot of Fords I've seen come with amps. The Expedition being a relatively high end vehicle should have one installed from the factory.

My model does have an amp somewhere, since I did have to connect the amp wire to the head unit when I installed an aftermarket head unit a few months ago. Assuming I can locate the amp, how do I test it? Also, I'm pretty sure I heard the pop coming from behind me, so I don't think it was the head unit. Would the head unit still appear to be functioning normally on the LCD if it had fried?

If the head unit's internal amp was fried, then yes, but since you said there's a factory amp, I'd go with it as the culprit. You can probably do a search online for where it is located in the vehicle.

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  • The stock head unit did not have a built in amp, as it relied entirely on the separate factory amp unit that is installed deeper inside the dash. When I installed an aftermarket head unit a few months ago, which did have its own internal amp, that resulted in a lot more power being run through the factory amp than it was designed for. This eventually fried the factory amp.
    – Timothy
    Mar 25, 2015 at 0:44
  • I solved the problem by running new wires directly from my head unit to the four doors, so that the head unit is wired directly to the speakers. It all works fine now, and as an added bonus the sound from the speakers is so much better now. The factory amp was definitely degrading the audio signal quality.
    – Timothy
    Mar 25, 2015 at 0:44
  • Awesome! I'm glad you were able to get to get it fixed :D
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Mar 25, 2015 at 0:59

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