Lights come on, Audio goes out

March 16, 2007 12:05 PM

Car Audio Filter: I have a 2003 Ford F-150 with audio that drops out completely. The receiver still works when the audio goes out, just no audio from any of the speakers. The audio does return (so I don't think its a faulty speaker).

I get no sound from my speakers in some very strange circumstances. During daytime driving, I rarely have problems. I get audio from the speakers from both the radio and CD. However, when the sun goes down and the headlights are on (either manually or automatic) the audio output could stop at any time. Another situation where the audio stops is when it rains, although that may be a symptom of the sensors for the automatic lights. The strangest part of this is that if I take the truck out of gear, putting it in neutral, the audio returns to normal. I have even had instances where going over a rough bump may knock the audio out (or even bring it back if it was already out)

I've had the dealer look at this several times. They just tighten all the connections and say that electrical issues like this are close to impossible to troubleshoot. Where should I go to get this fixed? Is this even fixable?

posted by unceman to technology (9 comments total)

Sounds like your electrical system can't handle the load, faulty alternator? So when you have something other than the radio drawing power the head unit/amp stops getting enough juice to power the speakers.
posted by zeoslap at 12:14 PM on March 16, 2007

Although the whole bump thing sounds like a loose connection to whatever powers the speakers. Does the head unit turn off or just the audio? Is there a separate amp?
posted by zeoslap at 12:16 PM on March 16, 2007

If it is an electrical system overload, then turning the volume way down should probably bring the speakers back on. If it is an issue of a short, the breaker in the head unit will keep the speakers off until the short is no longer detected. Since this seems to happen regularly, I think your best bet is to disconnect the speakers at the head unit one by one and see which combination of disconnected speakers allows you to drive and listen to music without suffering from this problem.
posted by Derive the Hamiltonian of... at 12:27 PM on March 16, 2007

I have succesfully diagnosed a similar problem by disconnecting the speakers one by one. If you can get the sound system to stay in borked mode, this is better. I got it to do so, and then just yanked and re-connected speaker connections from the head unit until I pulled the front left door speaker connection and the sound came back on. I pulled apart the door, found the flawed wire insulation (my fault, I had installed the system myself), and fixed it. Your dealership is a giant striped pirate galleon full of flatulent clowns (or something appropriate) if they cannot diagnose this. Especially if they tell you such a thing is "impossible to troubleshoot." Seriously, what a bunch of wankers.
posted by Derive the Hamiltonian of... at 12:31 PM on March 16, 2007

Ummm, if everything is run through an amp, you do the same procedure as the head unit except for the amp.

I've also had the problem of the head unit and amp not being able to draw enough power. For me, this failure caused the sound to fluctuate and then die out. Your head unit or amp may react differently to a drop in voltage and current, but I would say in general a load problem is not likely to cause the same kind of sharp cut-out that a short is.

In any case, a car stereo system is not a very complicated array of electronics. While it may be difficult (and therefor) expensive to get to the components and wiring, actually troubleshooting something so simple and linear is not a big deal. I do all of my own troubleshooting, maybe someone can tell you where you should go to get it done by a competent professional if you don't think you can do it yourself.
posted by Derive the Hamiltonian of... at 12:41 PM on March 16, 2007

Especially if they tell you such a thing is "impossible to troubleshoot." Seriously, what a bunch of wankers.

I'd give them a bit more credit than that. Granted it's something they probably don't want to spend a lot of time at but intermittent problems can be extremely time consuming to troubleshoot, though of course not impossible.

To the OP, can you duplicate the problem at home? Since it seems somewhat related to other demands on the electrical system trying turning on everything you can at home; lights on high, wipers, AC with fan on high, radio up. If that causes the problem pop the hood and measure the voltage on the battery. It should be about 14 volts. If it's less than that, especially if it's under 12 then I'd suspect the alternator and/or battery. If the vehicle isn't under warranty replacing an alternator is actually a pretty easy DIY job and you can get a remanufactured one at an auto parts store for a fairly reasonable fee once you return the old and get the core charge back.
posted by 6550 at 12:43 PM on March 16, 2007

Claiming it's near impossible to troubleshoot doesn't make them wankers, it makes them realistic about the time involved in finding an intermittent short and the fact that most people don't want to spend $80 per hour for two to twenty hours of labor. Additionally, since it's an intermittent problem, they don't want to have the almost certain experience of seeming to fix it and then having you come back - after writing them a big honking check - and have it still be broken.

Now, that said, if this is still under warranty (or you first reported it during the warranty period) then under no circumstances should you let them off the hook! Check to see if your state has a lemon law - you might have some additional options if you've returned for service on the same issue three or more times.

If you're not covered and you just want this fixed at a reasonable price then the simplest thing to do is just install a stereo with all new wiring. All you need for a stereo system is a ground, variable power (when the car is on), constant power (to keep your radio presets stored), and the speaker wires to the various speakers. You need an antenna too, but the chances that this is your core issue are almost 0.

A live wire can be pulled from the battery easily and you can install a relay on the ignition lead easily too for your intermittent power. Speaker wire is cheap and it's more time consuming than it is hard to run.
posted by phearlez at 2:07 PM on March 16, 2007

Single ground = single point of failure. Some audio systems use a single ground wire for all the speakers. The head unit is most likely grounded seperately, and thus does not lose power.
posted by Gungho at 5:39 PM on March 16, 2007

My problems are limited to the speakers. I do not get any problems from any other electrical unit other than the audio.

The problem that I would face in troubleshooting is that when I recreate the problem (no audio), I would have to put the truck in PARK to begin the troubleshooting process that Derive mentioned, which would be enough to "reset" the speakers into an operational state.
posted by unceman at 7:17 AM on March 19, 2007